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<h2 class="titleHead">Vorbis I specification</h2>
<div class="author" ><span
-class="cmr-17">Xiph.org Foundation</span></div>
-<br />
+class="cmr-17">Xiph.Org Foundation</span></div><br />
<div class="date" ><span
-class="cmr-17">January 25, 2010</span></div>
+class="cmr-17">February 3, 2012</span></div>
</div>
<h3 class="likesectionHead"><a
id="x1-1000"></a>Contents</h3>
href="#x1-120001.2.1" id="QQ2-1-13">Global Config</a></span>
<br />   <span class="subsubsectionToc" >1.2.2 <a
href="#x1-130001.2.2" id="QQ2-1-14">Mode</a></span>
+<br />   <span class="subsubsectionToc" >1.2.3 <a
+href="#x1-140001.2.3" id="QQ2-1-15">Mapping</a></span>
-<br />   <span class="subsubsectionToc" >1.2.3 <a
-href="#x1-140001.2.3" id="QQ2-1-15">Mapping</a></span>
<br />   <span class="subsubsectionToc" >1.2.4 <a
href="#x1-150001.2.4" id="QQ2-1-16">Floor</a></span>
<br />   <span class="subsubsectionToc" >1.2.5 <a
href="#x1-610004.2.1" id="QQ2-1-66">Common header decode</a></span>
<br />   <span class="subsubsectionToc" >4.2.2 <a
href="#x1-620004.2.2" id="QQ2-1-67">Identification header</a></span>
+<br />   <span class="subsubsectionToc" >4.2.3 <a
+href="#x1-630004.2.3" id="QQ2-1-68">Comment header</a></span>
-<br />   <span class="subsubsectionToc" >4.2.3 <a
-href="#x1-630004.2.3" id="QQ2-1-68">Comment header</a></span>
<br />   <span class="subsubsectionToc" >4.2.4 <a
href="#x1-640004.2.4" id="QQ2-1-69">Setup header</a></span>
<br />  <span class="subsectionToc" >4.3 <a
<br />   <span class="subsubsectionToc" >4.3.7 <a
href="#x1-780004.3.7" id="QQ2-1-84">inverse MDCT</a></span>
<br />   <span class="subsubsectionToc" >4.3.8 <a
-href="#x1-790004.3.8" id="QQ2-1-85">overlap˙add</a></span>
+href="#x1-790004.3.8" id="QQ2-1-85">overlap_add</a></span>
<br />   <span class="subsubsectionToc" >4.3.9 <a
href="#x1-800004.3.9" id="QQ2-1-86">output channel order</a></span>
<br /> <span class="sectionToc" >5 <a
href="#x1-980007.2.1" id="QQ2-1-104">model</a></span>
<br />   <span class="subsubsectionToc" >7.2.2 <a
href="#x1-990007.2.2" id="QQ2-1-109">header decode</a></span>
+<br />   <span class="subsubsectionToc" >7.2.3 <a
+href="#x1-1000007.2.3" id="QQ2-1-110">packet decode</a></span>
+<br />   <span class="subsubsectionToc" >7.2.4 <a
+href="#x1-1010007.2.4" id="QQ2-1-111">curve computation</a></span>
<br /> <span class="sectionToc" >8 <a
href="#x1-1020008" id="QQ2-1-112">Residue setup and decode</a></span>
<br />  <span class="subsectionToc" >8.1 <a
<br />   <span class="subsubsectionToc" >9.2.1 <a
href="#x1-1170009.2.1" id="QQ2-1-129">ilog</a></span>
<br />   <span class="subsubsectionToc" >9.2.2 <a
-href="#x1-1180009.2.2" id="QQ2-1-130">float32˙unpack</a></span>
+href="#x1-1180009.2.2" id="QQ2-1-130">float32_unpack</a></span>
<br />   <span class="subsubsectionToc" >9.2.3 <a
-href="#x1-1190009.2.3" id="QQ2-1-131">lookup1˙values</a></span>
+href="#x1-1190009.2.3" id="QQ2-1-131">lookup1_values</a></span>
<br />   <span class="subsubsectionToc" >9.2.4 <a
-href="#x1-1200009.2.4" id="QQ2-1-132">low˙neighbor</a></span>
+href="#x1-1200009.2.4" id="QQ2-1-132">low_neighbor</a></span>
<br />   <span class="subsubsectionToc" >9.2.5 <a
-href="#x1-1210009.2.5" id="QQ2-1-133">high˙neighbor</a></span>
+href="#x1-1210009.2.5" id="QQ2-1-133">high_neighbor</a></span>
<br />   <span class="subsubsectionToc" >9.2.6 <a
-href="#x1-1220009.2.6" id="QQ2-1-134">render˙point</a></span>
+href="#x1-1220009.2.6" id="QQ2-1-134">render_point</a></span>
<br />   <span class="subsubsectionToc" >9.2.7 <a
-href="#x1-1230009.2.7" id="QQ2-1-135">render˙line</a></span>
+href="#x1-1230009.2.7" id="QQ2-1-135">render_line</a></span>
<br /> <span class="sectionToc" >10 <a
href="#x1-12400010" id="QQ2-1-136">Tables</a></span>
<br />  <span class="subsectionToc" >10.1 <a
href="#x1-128000A.1.1" id="QQ2-1-140">Restrictions</a></span>
<br />   <span class="subsubsectionToc" >A.1.2 <a
href="#x1-129000A.1.2" id="QQ2-1-141">MIME type</a></span>
-<br />  <span class="subsectionToc" >A.2 <a
-href="#x1-130000A.2" id="QQ2-1-142">Encapsulation</a></span>
+<br />  <span class="subsectionToc" >A.2 <a
+href="#x1-130000A.2" id="QQ2-1-142">Encapsulation</a></span>
<br /> <span class="sectionToc" >B <a
href="#x1-132000B" id="QQ2-1-144">Vorbis encapsulation in RTP</a></span>
</div>
-<h3 class="sectionHead"><span class="titlemark">1 </span> <a
+<h3 class="sectionHead"><span class="titlemark">1
. </span> <a
id="x1-20001"></a>Introduction and Description</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">1.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">1.1
. </span> <a
id="x1-30001.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >This document provides a high level description of the Vorbis codec’s construction. A bit-by-bit
specification appears beginning in <a
sections assume a high-level understanding of the Vorbis decode process, which is provided
here.
<!--l. 15--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.1
. </span> <a
id="x1-40001.1.1"></a>Application</h5>
<!--l. 16--><p class="noindent" >Vorbis is a general purpose perceptual audio CODEC intended to allow maximum encoder
flexibility, thus allowing it to scale competitively over an exceptionally wide range of bitrates. At
representations (monaural, polyphonic, stereo, quadraphonic, 5.1, ambisonic, or up to 255
discrete channels).
<!--l. 29--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.2
. </span> <a
id="x1-50001.1.2"></a>Classification</h5>
<!--l. 30--><p class="noindent" >Vorbis I is a forward-adaptive monolithic transform CODEC based on the Modified Discrete
Cosine Transform. The codec is structured to allow addition of a hybrid wavelet filterbank in
<!--l. 37--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.3
. </span> <a
id="x1-60001.1.3"></a>Assumptions</h5>
<!--l. 39--><p class="noindent" >The Vorbis CODEC design assumes a complex, psychoacoustically-aware encoder and simple,
low-complexity decoder. Vorbis decode is computationally simpler than mp3, although it does
“<a
href="#x1-126000A">Embedding Vorbis into an Ogg stream<!--tex4ht:ref: vorbis:over:ogg --></a>”.
<!--l. 77--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.4
. </span> <a
id="x1-70001.1.4"></a>Codec Setup and Probability Model</h5>
<!--l. 79--><p class="noindent" >Vorbis’ heritage is as a research CODEC and its current design reflects a desire to allow multiple
decades of continuous encoder improvement before running out of room within the codec
designs, such as Windows’ ACM codec framework). However, we find that it does not
fundamentally limit Vorbis’ suitable application space.
<!--l. 115--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.5 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.5
. </span> <a
id="x1-90001.1.5"></a>Format Specification</h5>
<!--l. 116--><p class="noindent" >The Vorbis format is well-defined by its decode specification; any encoder that produces packets
that are correctly decoded by the reference Vorbis decoder described below may be considered
specification defined below (except where noted) to be considered a proper Vorbis
decoder.
<!--l. 123--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.1.6 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.1.6
. </span> <a
id="x1-100001.1.6"></a>Hardware Profile</h5>
the ‘full’ decode specification yet still be certified compliant. These optional omissions are
labelled in the spec where relevant.
<!--l. 131--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">1.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">1.2
. </span> <a
id="x1-110001.2"></a>Decoder Configuration</h4>
<!--l. 133--><p class="noindent" >Decoder setup consists of configuration of multiple, self-contained component abstractions that
perform specific functions in the decode pipeline. Each different component instance of a specific
class="content">decoder pipeline configuration</span></div><!--tex4ht:label?: x1-110011 -->
</div>
<!--l. 146--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.1
. </span> <a
id="x1-120001.2.1"></a>Global Config</h5>
<!--l. 147--><p class="noindent" >Global codec configuration consists of a few audio related fields (sample rate, channels), Vorbis
version (always ’0’ in Vorbis I), bitrate hints, and the lists of component instances. All other
configuration is in the context of specific components.
<!--l. 152--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.2
. </span> <a
id="x1-130001.2.2"></a>Mode</h5>
number. The mapping number specifies which mapping configuration instance to use for low-level
packet decode and synthesis.
<!--l. 171--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.3
. </span> <a
id="x1-140001.2.3"></a>Mapping</h5>
<!--l. 173--><p class="noindent" >A mapping contains a channel coupling description and a list of ’submaps’ that bundle sets
of channel vectors together for grouped encoding and decoding. These submaps are
<!--l. 199--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.4
. </span> <a
id="x1-150001.2.4"></a>Floor</h5>
<!--l. 201--><p class="noindent" >Vorbis encodes a spectral ’floor’ vector for each PCM channel. This vector is a low-resolution
representation of the audio spectrum for the given channel in the current frame, generally used
high bitrate modes. Floor 1 is also considerably less expensive to decode than floor
0.
<!--l. 218--><p class="noindent" >Floor 0 is not to be considered deprecated, but it is of limited modern use. No known Vorbis
-encoder past Xiph.org’s own beta 4 makes use of floor 0.
+encoder past Xiph.Org’s own beta 4 makes use of floor 0.
<!--l. 222--><p class="noindent" >The values coded/decoded by a floor are both compactly formatted and make use of entropy
coding to save space. For this reason, a floor configuration generally refers to multiple
codebooks in the codebook component list. Entropy coding is thus provided as an
abstraction, and each floor instance may choose from any and all available codebooks when
coding/decoding.
<!--l. 230--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.5 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.5
. </span> <a
id="x1-160001.2.5"></a>Residue</h5>
<!--l. 231--><p class="noindent" >The spectral residue is the fine structure of the audio spectrum once the floor curve has been
subtracted out. In simplest terms, it is coded in the bitstream using cascaded (multi-pass) vector
-<h5 class="subsubsectionHead"><span class="titlemark">1.2.6 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.2.6
. </span> <a
id="x1-170001.2.6"></a>Codebooks</h5>
<!--l. 243--><p class="noindent" >Codebooks are a self-contained abstraction that perform entropy decoding and, optionally, use
the entropy-decoded integer value as an offset into an index of output value vectors, returning
the vector index is encoded as a single list of values of possible values that are then permuted
into a list of n-dimensional rows (lattice VQ).
<!--l. 260--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">1.3 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">1.3
. </span> <a
id="x1-180001.3"></a>High-level Decode Process</h4>
<!--l. 262--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.3.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.3.1
. </span> <a
id="x1-190001.3.1"></a>Decode Setup</h5>
<!--l. 264--><p class="noindent" >Before decoding can begin, a decoder must initialize using the bitstream headers matching the
stream to be decoded. Vorbis uses three header packets; all are required, in-order, by
The setup header includes extensive CODEC setup information as well as the complete VQ and
Huffman codebooks needed for decode.
<!--l. 289--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">1.3.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">1.3.2
. </span> <a
id="x1-230001.3.2"></a>Decode Procedure</h5>
<!--l. 291--><p class="noindent" >The decoding and synthesis procedure for all audio packets is fundamentally the same.
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-23002x1">decode packet type flag
- </li>
- <li
- class="enumerate" id="x1-23004x2">decode mode number
- </li>
- <li
- class="enumerate" id="x1-23006x3">decode window shape (long windows only)
- </li>
- <li
- class="enumerate" id="x1-23008x4">decode floor
- </li>
- <li
- class="enumerate" id="x1-23010x5">decode residue into residue vectors
- </li>
- <li
- class="enumerate" id="x1-23012x6">inverse channel coupling of residue vectors
- </li>
- <li
- class="enumerate" id="x1-23014x7">generate floor curve from decoded floor data
- </li>
- <li
- class="enumerate" id="x1-23016x8">compute dot product of floor and residue, producing audio spectrum vector
- </li>
- <li
- class="enumerate" id="x1-23018x9">inverse monolithic transform of audio spectrum vector, always an MDCT in Vorbis
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">decode packet type flag
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">decode mode number
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">decode window shape (long windows only)
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">decode floor
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem">decode residue into residue vectors
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem">inverse channel coupling of residue vectors
+ </dd><dt class="enumerate-enumitem">
+ 7. </dt><dd
+class="enumerate-enumitem">generate floor curve from decoded floor data
+ </dd><dt class="enumerate-enumitem">
+ 8. </dt><dd
+class="enumerate-enumitem">compute dot product of floor and residue, producing audio spectrum vector
+ </dd><dt class="enumerate-enumitem">
+ 9. </dt><dd
+class="enumerate-enumitem">inverse monolithic transform of audio spectrum vector, always an MDCT in Vorbis
I
- </li>
- <li
- class="enumerate" id="x1-23020x10">overlap/add left-hand output of transform with right-hand output of previous frame
- </li>
- <li
- class="enumerate" id="x1-23022x11">store right hand-data from transform of current frame for future lapping
- </li>
- <li
- class="enumerate" id="x1-23024x12">if not first frame, return results of overlap/add as audio result of current frame</li></ol>
+ </dd><dt class="enumerate-enumitem">
+ 10. </dt><dd
+class="enumerate-enumitem">overlap/add left-hand output of transform with right-hand output of previous frame
+ </dd><dt class="enumerate-enumitem">
+ 11. </dt><dd
+class="enumerate-enumitem">store right hand-data from transform of current frame for future lapping
+ </dd><dt class="enumerate-enumitem">
+ 12. </dt><dd
+class="enumerate-enumitem">if not first frame, return results of overlap/add as audio result of current frame</dd></dl>
<!--l. 308--><p class="noindent" >Note that clever rearrangement of the synthesis arithmetic is possible; as an example, one can
take advantage of symmetries in the MDCT to store the right-hand transform data of a partial
MDCT for a 50% inter-frame buffer space savings, and then complete the transform later before
-<h3 class="sectionHead"><span class="titlemark">2 </span> <a
+<h3 class="sectionHead"><span class="titlemark">2
. </span> <a
id="x1-360002"></a>Bitpacking Convention</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">2.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">2.1
. </span> <a
id="x1-370002.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >The Vorbis codec uses relatively unstructured raw packets containing arbitrary-width binary
integer fields. Logically, these packets are a bitstream in which bits are coded one-by-one by the
bitpacking convention specifies the correct mapping of the logical packet bitstream into an actual
representation in fixed-width words.
<!--l. 19--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.1
. </span> <a
id="x1-380002.1.1"></a>octets, bytes and words</h5>
<!--l. 21--><p class="noindent" >In most contemporary architectures, a ’byte’ is synonymous with an ’octet’, that is, eight bits.
This has not always been the case; seven, ten, eleven and sixteen bit ’bytes’ have been used.
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.2
. </span> <a
id="x1-390002.1.2"></a>bit order</h5>
<!--l. 41--><p class="noindent" >A byte has a well-defined ’least significant’ bit (LSb), which is the only bit set when the byte is
storing the two’s complement integer value +1. A byte’s ’most significant’ bit (MSb) is at the
class="cmmi-12">n </span>= 7 in an
octet) for the MSb.
<!--l. 50--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.3
. </span> <a
id="x1-400002.1.3"></a>byte order</h5>
<!--l. 52--><p class="noindent" >Words are native groupings of multiple bytes. Several byte orderings are possible in a word; the
common ones are 3-2-1-0 (’big endian’ or ’most significant byte first’ in which the
<span
class="cmmi-12">n</span>.
<!--l. 68--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.4
. </span> <a
id="x1-410002.1.4"></a>coding bits into byte sequences</h5>
<!--l. 70--><p class="noindent" >The Vorbis codec has need to code arbitrary bit-width integers, from zero to 32 bits
wide, into packets. These integer fields are not aligned to the boundaries of the byte
as encoding, but by reading bits from the byte stream and reassembling them into
integers.
<!--l. 90--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.5 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.5
. </span> <a
id="x1-420002.1.5"></a>signedness</h5>
<!--l. 92--><p class="noindent" >The signedness of a specific number resulting from decode is to be interpreted by the decoder
given decode context. That is, the three bit binary pattern ’b111’ can be taken to represent
encoder and decoder are responsible for knowing if fields are to be treated as signed or
unsigned.
<!--l. 101--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.6 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.6
. </span> <a
id="x1-430002.1.6"></a>coding example</h5>
<!--l. 103--><p class="noindent" >Code the 4 bit integer value ’12’ [b1100] into an empty bytestream. Bytestream result:
<!--l. 106--><p class="noindent" >
class="cmtt-8"> </span>
</div>
<!--l. 173--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.7 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.7
. </span> <a
id="x1-440002.1.7"></a>decoding example</h5>
<!--l. 175--><p class="noindent" >Reading from the beginning of the bytestream encoded in the above example:
<!--l. 177--><p class="noindent" >
either as the unsigned value ’3’, or the signed value ’-1’. Signedness is dependent on
decode context.</li></ul>
<!--l. 208--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.8 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.8
. </span> <a
id="x1-450002.1.8"></a>end-of-packet alignment</h5>
<!--l. 210--><p class="noindent" >The typical use of bitpacking is to produce many independent byte-aligned packets which are
embedded into a larger byte-aligned container structure, such as an Ogg transport bitstream.
<!--l. 233--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">2.1.9 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">2.1.9
. </span> <a
id="x1-460002.1.9"></a>reading zero bits</h5>
<!--l. 235--><p class="noindent" >Reading a zero-bit-wide integer returns the value ’0’ and does not increment the stream cursor.
Reading to the end of the packet (but not past, such that an ’end-of-packet’ condition has not
-<h3 class="sectionHead"><span class="titlemark">3 </span> <a
+<h3 class="sectionHead"><span class="titlemark">3
. </span> <a
id="x1-470003"></a>Probability Model and Codebooks</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">3.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">3.1
. </span> <a
id="x1-480003.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >Unlike practically every other mainstream audio codec, Vorbis has no statically configured
probability model, instead packing all entropy decoding configuration, VQ and Huffman, into the
decoded Huffman value is applied as an offset, generating the final decoded output corresponding
to a given compressed codeword.
<!--l. 18--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">3.1.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">3.1.1
. </span> <a
id="x1-490003.1.1"></a>Bitwise operation</h5>
<!--l. 19--><p class="noindent" >The codebook mechanism is built on top of the vorbis bitpacker. Both the codebooks themselves
and the codewords they decode are unrolled from a packet as a series of arbitrary-width values
href="#x1-360002">Section 2</a>, “<a
href="#x1-360002">Bitpacking Convention<!--tex4ht:ref: vorbis:spec:bitpacking --></a>”.
<!--l. 27--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">3.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">3.2
. </span> <a
id="x1-500003.2"></a>Packed codebook format</h4>
<!--l. 29--><p class="noindent" >For purposes of the examples below, we assume that the storage system’s native byte width is
eight bits. This is not universally true; see <a
<!--l. 34--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">3.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">3.2.1
. </span> <a
id="x1-510003.2.1"></a>codebook decode</h5>
<!--l. 36--><p class="noindent" >A codebook begins with a 24 bit sync pattern, 0x564342:
<!--l. 38--><p class="noindent" >
</li></ul>
<!--l. 136--><p class="noindent" >After all codeword lengths have been decoded, the decoder reads the vector lookup table. Vorbis
I supports three lookup types:
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-51098x1">No lookup
- </li>
- <li
- class="enumerate" id="x1-51100x2">Implicitly populated value mapping (lattice VQ)
- </li>
- <li
- class="enumerate" id="x1-51102x3">Explicitly populated value mapping (tessellated or ’foam’ VQ)</li></ol>
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">No lookup
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">Implicitly populated value mapping (lattice VQ)
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">Explicitly populated value mapping (tessellated or ’foam’ VQ)</dd></dl>
<!--l. 149--><p class="noindent" >The lookup table type is read as a four bit unsigned integer:
<div class="fancyvrb" id="fancyvrb13">
<a
- id="x1-51104r1"></a><span
+ id="x1-51101r1"></a><span
class="cmr-6">1</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
<!--l. 168--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb14">
<a
- id="x1-51106r1"></a><span
+ id="x1-51103r1"></a><span
class="cmr-6">1</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> unsigned</span><span
class="cmtt-8"> integer)</span>
<br class="fancyvrb" /><a
- id="x1-51108r2"></a><span
+ id="x1-51105r2"></a><span
class="cmr-6">2</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> unsigned</span><span
class="cmtt-8"> integer)</span>
<br class="fancyvrb" /><a
- id="x1-51110r3"></a><span
+ id="x1-51107r3"></a><span
class="cmr-6">3</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> add</span><span
class="cmtt-8"> 1</span>
<br class="fancyvrb" /><a
- id="x1-51112r4"></a><span
+ id="x1-51109r4"></a><span
class="cmr-6">4</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> boolean</span><span
class="cmtt-8"> flag</span>
<br class="fancyvrb" /><a
- id="x1-51114r5"></a><span
+ id="x1-51111r5"></a><span
class="cmr-6">5</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51116r6"></a><span
+ id="x1-51113r6"></a><span
class="cmr-6">6</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmsy-8">{</span>
<br class="fancyvrb" /><a
- id="x1-51118r7"></a><span
+ id="x1-51115r7"></a><span
class="cmr-6">7</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51120r8"></a><span
+ id="x1-51117r8"></a><span
class="cmr-6">8</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> [codebook_dimensions]</span><span
class="cmtt-8"> )</span>
<br class="fancyvrb" /><a
- id="x1-51122r9"></a><span
+ id="x1-51119r9"></a><span
class="cmr-6">9</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51124r10"></a><span
+ id="x1-51121r10"></a><span
class="cmr-6">10</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmsy-8">{</span>
<br class="fancyvrb" /><a
- id="x1-51126r11"></a><span
+ id="x1-51123r11"></a><span
class="cmr-6">11</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51128r12"></a><span
+ id="x1-51125r12"></a><span
class="cmr-6">12</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> *</span><span
class="cmtt-8"> [codebook_dimensions]</span>
<br class="fancyvrb" /><a
- id="x1-51130r13"></a><span
+ id="x1-51127r13"></a><span
class="cmr-6">13</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51132r14"></a><span
+ id="x1-51129r14"></a><span
class="cmr-6">14</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmsy-8">}</span>
<br class="fancyvrb" /><a
- id="x1-51134r15"></a><span
+ id="x1-51131r15"></a><span
class="cmr-6">15</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-51136r16"></a><span
+ id="x1-51133r16"></a><span
class="cmr-6">16</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
<br class="fancyvrb" /><a
- id="x1-51138r17"></a><span
+ id="x1-51135r17"></a><span
class="cmr-6">17</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmr-6">1</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> the</span><span
-class="cmtt-8"> [codebook_multiplicands]</span><span
+class="cmtt-8"> [codebook\_multiplicands]</span><span
class="cmtt-8"> array</span>
<br class="fancyvrb" /><a
id="x1-54004r2"></a><span
class="cmr-6">2</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_minimum_value]</span>
+class="cmtt-8"> [codebook\_minimum\_value]</span>
<br class="fancyvrb" /><a
id="x1-54006r3"></a><span
class="cmr-6">3</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_delta_value]</span>
+class="cmtt-8"> [codebook\_delta\_value]</span>
<br class="fancyvrb" /><a
id="x1-54008r4"></a><span
class="cmr-6">4</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_sequence_p]</span>
+class="cmtt-8"> [codebook\_sequence\_p]</span>
<br class="fancyvrb" /><a
id="x1-54010r5"></a><span
class="cmr-6">5</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_lookup_type]</span>
+class="cmtt-8"> [codebook\_lookup\_type]</span>
<br class="fancyvrb" /><a
id="x1-54012r6"></a><span
class="cmr-6">6</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_entries]</span>
+class="cmtt-8"> [codebook\_entries]</span>
<br class="fancyvrb" /><a
id="x1-54014r7"></a><span
class="cmr-6">7</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_dimensions]</span>
+class="cmtt-8"> [codebook\_dimensions]</span>
<br class="fancyvrb" /><a
id="x1-54016r8"></a><span
class="cmr-6">8</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> [codebook_lookup_values]</span>
+class="cmtt-8"> [codebook\_lookup\_values]</span>
</div>
<!--l. 297--><p class="noindent" >Decoding (unpacking) a specific vector in the vector lookup table proceeds according to
<span
class="cmtt-8"> completed.</span>
</div>
<!--l. 370--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">3.3 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">3.3
. </span> <a
id="x1-570003.3"></a>Use of the codebook abstraction</h4>
<!--l. 372--><p class="noindent" >The decoder uses the codebook abstraction much as it does the bit-unpacking convention; a
specific codebook reads a codeword from the bitstream, decoding it into an entry number, and
-<h3 class="sectionHead"><span class="titlemark">4 </span> <a
+<h3 class="sectionHead"><span class="titlemark">4
. </span> <a
id="x1-580004"></a>Codec Setup and Packet Decode</h3>
<!--l. 7--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">4.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">4.1
. </span> <a
id="x1-590004.1"></a>Overview</h4>
<!--l. 9--><p class="noindent" >This document serves as the top-level reference document for the bit-by-bit decode specification
of Vorbis I. This document assumes a high-level understanding of the Vorbis decode
href="#x1-360002">Bitpacking Convention<!--tex4ht:ref: vorbis:spec:bitpacking --></a>” covers reading and writing bit fields from and to bitstream
packets.
<!--l. 17--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">4.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">4.2
. </span> <a
id="x1-600004.2"></a>Header decode and decode setup</h4>
<!--l. 19--><p class="noindent" >A Vorbis bitstream begins with three header packets. The header packets are, in order, the
identification header, the comments header, and the setup header. All are required for decode
the stream undecodable. End-of-packet decoding the comment header is a non-fatal error
condition.
<!--l. 26--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.2.1
. </span> <a
id="x1-610004.2.1"></a>Common header decode</h5>
<!--l. 28--><p class="noindent" >Each header packet begins with the same header fields.
<!--l. 31--><p class="noindent" >
single bit of ’0’ is an audio packet). The packets must occur in the order of identification,
comment, setup.
<!--l. 44--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.2.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.2.2
. </span> <a
id="x1-620004.2.2"></a>Identification header</h5>
<!--l. 46--><p class="noindent" >The identification header is a short header of only a few fields used to declare the stream
definitively as Vorbis, and provide a few externally relevant pieces of information about the audio
</li>
<li class="itemize">None set indicates the encoder does not care to speculate.</li></ul>
<!--l. 85--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.2.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.2.3
. </span> <a
id="x1-630004.2.3"></a>Comment header</h5>
<!--l. 86--><p class="noindent" >Comment header decode and data specification is covered in <a
href="#x1-810005">Section 5</a>, “<a
href="#x1-810005">comment field and
header specification<!--tex4ht:ref: vorbis:spec:comment --></a>”.
<!--l. 90--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.2.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.2.4
. </span> <a
id="x1-640004.2.4"></a>Setup header</h5>
<!--l. 92--><p class="noindent" >Vorbis codec setup is configurable to an extreme degree:
<div class="center"
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-65002x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_codebook_count] </span>= read eight bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-65004x2">Decode <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">Decode <span
class="cmtt-12">[vorbis_codebook_count] </span>codebooks in order as defined in <a
href="#x1-470003">Section 3</a>,
“<a
href="#x1-470003">Probability Model and Codebooks<!--tex4ht:ref: vorbis:spec:codebook --></a>”. Save each configuration, in order, in an array
of codebook configurations <span
-class="cmtt-12">[vorbis_codebook_configurations]</span>.</li></ol>
+class="cmtt-12">[vorbis_codebook_configurations]</span>.</dd></dl>
<!--l. 120--><p class="noindent" ><span class="paragraphHead"><a
id="x1-660004.2.4"></a><span
class="cmbx-12">Time domain transforms</span></span>
These hooks are placeholders in Vorbis I. Nevertheless, the configuration placeholder values must
be read to maintain bitstream sync.
-<!--l. 12
6--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-66002x1"><span
+<!--l. 12
7--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_time_count] </span>= read 6 bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-66004x2">read <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">read <span
class="cmtt-12">[vorbis_time_count] </span>16 bit values; each value should be zero. If any value is
- nonzero, this is an error condition and the stream is undecodable.</li></ol>
+ nonzero, this is an error condition and the stream is undecodable.</dd></dl>
<!--l. 133--><p class="noindent" ><span class="paragraphHead"><a
id="x1-670004.2.4"></a><span
class="cmbx-12">Floors</span></span>
Vorbis uses two floor types; header decode is handed to the decode abstraction of the appropriate
type.
-<!--l. 13
8--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-67002x1"><span
+<!--l. 13
9--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_floor_count] </span>= read 6 bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-67004x2">For each <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">For each <span
class="cmtt-12">[i] </span>of <span
class="cmtt-12">[vorbis_floor_count] </span>floor numbers:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-67006x1">read the floor type: vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">read the floor type: vector <span
class="cmtt-12">[vorbis_floor_types] </span>element <span
class="cmtt-12">[i] </span>= read 16 bits
as unsigned integer
- </li>
- <li
-
class="enumerate" id="x1-67008x2">If the floor type is zero, decode the floor configuration as defined in <a
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+
class="enumerate-enumitem">If the floor type is zero, decode the floor configuration as defined in <a
href="#x1-890006">Section 6</a>,
“<a
href="#x1-890006">Floor type 0 setup and decode<!--tex4ht:ref: vorbis:spec:floor0 --></a>”; save this configuration in slot <span
- </li>
- <li
-
class="enumerate" id="x1-67010x3">If the floor type is one, decode the floor configuration as defined in <a
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+
class="enumerate-enumitem">If the floor type is one, decode the floor configuration as defined in <a
href="#x1-950007">Section 7</a>,
“<a
href="#x1-950007">Floor type 1 setup and decode<!--tex4ht:ref: vorbis:spec:floor1 --></a>”; save this configuration in slot <span
class="cmtt-12">[i] </span>of the floor
configuration array <span
class="cmtt-12">[vorbis_floor_configurations]</span>.
- </li>
- <li
- class="enumerate" id="x1-67012x4">If the the floor type is greater than one, this stream is undecodable; ERROR
- CONDITION</li></ol>
- </li></ol>
+ </dd><dt class="enumerate-enumitem">
+ d) </dt><dd
+class="enumerate-enumitem">If the the floor type is greater than one, this stream is undecodable; ERROR
+ CONDITION</dd></dl>
+ </dd></dl>
<!--l. 157--><p class="noindent" ><span class="paragraphHead"><a
id="x1-680004.2.4"></a><span
class="cmbx-12">Residues</span></span>
Vorbis uses three residue types; header decode of each type is identical.
-<!--l. 16
2--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-68002x1"><span
+<!--l. 16
3--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_residue_count] </span>= read 6 bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-68004x2">For each of <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">For each of <span
class="cmtt-12">[vorbis_residue_count] </span>residue numbers:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-68006x1">read the residue type; vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">read the residue type; vector <span
class="cmtt-12">[vorbis_residue_types] </span>element <span
class="cmtt-12">[i] </span>= read 16
bits as unsigned integer
- </li>
- <li
- class="enumerate" id="x1-68008x2">If the residue type is zero, one or two, decode the residue configuration as defined
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem">If the residue type is zero, one or two, decode the residue configuration as defined
in <a
href="#x1-1020008">Section 8</a>, “<a
href="#x1-1020008">Residue setup and decode<!--tex4ht:ref: vorbis:spec:residue --></a>”; save this configuration in slot <span
class="cmtt-12">[i] </span>of
the residue configuration array <span
class="cmtt-12">[vorbis_residue_configurations]</span>.
- </li>
- <li
- class="enumerate" id="x1-68010x3">If the the residue type is greater than two, this stream is undecodable; ERROR
- CONDITION</li></ol>
- </li></ol>
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem">If the the residue type is greater than two, this stream is undecodable; ERROR
+ CONDITION</dd></dl>
+ </dd></dl>
<!--l. 177--><p class="noindent" ><span class="paragraphHead"><a
id="x1-690004.2.4"></a><span
class="cmbx-12">Mappings</span></span>
-<!--l. 18
7--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-69002x1"><span
+<!--l. 18
8--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mapping_count] </span>= read 6 bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-69004x2">For each <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">For each <span
class="cmtt-12">[i] </span>of <span
class="cmtt-12">[vorbis_mapping_count] </span>mapping numbers:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-69006x1">read the mapping type: 16 bits as unsigned integer. There’s no reason to save
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">read the mapping type: 16 bits as unsigned integer. There’s no reason to save
the mapping type in Vorbis I.
- </li>
- <li
- class="enumerate" id="x1-69008x2">If the mapping type is nonzero, the stream is undecodable
- </li>
- <li
- class="enumerate" id="x1-69010x3">If the mapping type is zero:
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-69012x1">read 1 bit as a boolean flag
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-69014x1">if set, <span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem">If the mapping type is nonzero, the stream is undecodable
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem">If the mapping type is zero:
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">read 1 bit as a boolean flag
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">if set, <span
class="cmtt-12">[vorbis_mapping_submaps] </span>= read 4 bits as unsigned integer
and add one
- </li>
- <li
- class="enumerate" id="x1-69016x2">if unset, <span
-class="cmtt-12">[vorbis_mapping_submaps] </span>= 1</li></ol>
- </li>
- <li
- class="enumerate" id="x1-69018x2">read 1 bit as a boolean flag
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-69020x1">if set, square polar channel mapping is in use:
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem">if unset, <span
+class="cmtt-12">[vorbis_mapping_submaps] </span>= 1</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ ii. </dt><dd
+class="enumerate-enumitem">read 1 bit as a boolean flag
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">if set, square polar channel mapping is in use:
<ul class="itemize1">
<li class="itemize"><span
class="cmtt-12">[vorbis_mapping_coupling_steps] </span>= read 8 bits as unsigned
class="cmtt-12">[audio_channels]</span>-1, the stream
is undecodable.</li></ul>
</li></ul>
- </li>
- <li
- class="enumerate" id="x1-69022x2">if unset, <span
-class="cmtt-12">[vorbis_mapping_coupling_steps] </span>= 0</li></ol>
- </li>
- <li
- class="enumerate" id="x1-69024x3">read 2 bits (reserved field); if the value is nonzero, the stream is undecodable
- </li>
- <li
- class="enumerate" id="x1-69026x4">if <span
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem">if unset, <span
+class="cmtt-12">[vorbis_mapping_coupling_steps] </span>= 0</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ iii. </dt><dd
+class="enumerate-enumitem">read 2 bits (reserved field); if the value is nonzero, the stream is undecodable
+ </dd><dt class="enumerate-enumitem">
+ iv. </dt><dd
+class="enumerate-enumitem">if <span
class="cmtt-12">[vorbis_mapping_submaps] </span>is greater than one, we read channel multiplex
settings. For each <span
class="cmtt-12">[j] </span>of <span
class="cmtt-12">[audio_channels] </span>channels:
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-69028x1">vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">vector <span
class="cmtt-12">[vorbis_mapping_mux] </span>element <span
class="cmtt-12">[j] </span>= read 4 bits as unsigned
integer
- </li>
- <li
- class="enumerate" id="x1-69030x2">if the value is greater than the highest numbered submap
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem">if the value is greater than the highest numbered submap
(<span
class="cmtt-12">[vorbis_mapping_submaps] </span>- 1), this in an error condition rendering
- the stream undecodable</li></ol>
- </li>
- <li
- class="enumerate" id="x1-69032x5">for each submap <span
+ the stream undecodable</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ v. </dt><dd
+class="enumerate-enumitem">for each submap <span
class="cmtt-12">[j] </span>of <span
class="cmtt-12">[vorbis_mapping_submaps] </span>submaps, read the floor and
residue numbers for use in decoding that submap:
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-69034x1">read and discard 8 bits (the unused time configuration placeholder)
- </li>
- <li
- class="enumerate" id="x1-69036x2">read 8 bits as unsigned integer for the floor number; save in vector
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">read and discard 8 bits (the unused time configuration placeholder)
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem">read 8 bits as unsigned integer for the floor number; save in vector
<span
class="cmtt-12">[vorbis_mapping_submap_floor] </span>element <span
class="cmtt-12">[j]</span>
- </li>
- <li
- class="enumerate" id="x1-69038x3">verify the floor number is not greater than the highest number floor
+ </dd><dt class="enumerate-enumitem">
+ C. </dt><dd
+class="enumerate-enumitem">verify the floor number is not greater than the highest number floor
configured for the bitstream. If it is, the bitstream is undecodable
- </li>
- <li
- class="enumerate" id="x1-69040x4">read 8 bits as unsigned integer for the residue number; save in vector
+ </dd><dt class="enumerate-enumitem">
+ D. </dt><dd
+class="enumerate-enumitem">read 8 bits as unsigned integer for the residue number; save in vector
<span
class="cmtt-12">[vorbis_mapping_submap_residue] </span>element <span
class="cmtt-12">[j]</span>
- </li>
- <li
- class="enumerate" id="x1-69042x5">verify the residue number is not greater than the highest number residue
- configured for the bitstream. If it is, the bitstream is undecodable</li></ol>
- </li>
- <li
- class="enumerate" id="x1-69044x6">save this mapping configuration in slot <span
+ </dd><dt class="enumerate-enumitem">
+ E. </dt><dd
+class="enumerate-enumitem">verify the residue number is not greater than the highest number residue
+ configured for the bitstream. If it is, the bitstream is undecodable</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ vi. </dt><dd
+class="enumerate-enumitem">save this mapping configuration in slot <span
class="cmtt-12">[i] </span>of the mapping configuration array
<span
-class="cmtt-12">[vorbis_mapping_configurations]</span>.</li></ol>
- </li></ol>
- </li></ol>
+class="cmtt-12">[vorbis_mapping_configurations]</span>.</dd></dl>
+ </dd></dl>
+ </dd></dl>
<!--l. 247--><p class="noindent" ><span class="paragraphHead"><a
id="x1-700004.2.4"></a><span
class="cmbx-12">Modes</span></span>
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-70002x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mode_count] </span>= read 6 bits as unsigned integer and add one
- </li>
- <li
- class="enumerate" id="x1-70004x2">For each of <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">For each of <span
class="cmtt-12">[vorbis_mode_count] </span>mode numbers:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-70006x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mode_blockflag] </span>= read 1 bit
- </li>
- <li
- class="enumerate" id="x1-70008x2"><span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mode_windowtype] </span>= read 16 bits as unsigned integer
- </li>
- <li
- class="enumerate" id="x1-70010x3"><span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mode_transformtype] </span>= read 16 bits as unsigned integer
- </li>
- <li
- class="enumerate" id="x1-70012x4"><span
+ </dd><dt class="enumerate-enumitem">
+ d) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[vorbis_mode_mapping] </span>= read 8 bits as unsigned integer
- </li>
- <li
- class="enumerate" id="x1-70014x5">verify ranges; zero is the only legal value in
+ </dd><dt class="enumerate-enumitem">
+ e) </dt><dd
+class="enumerate-enumitem">verify ranges; zero is the only legal value in
Vorbis I for <span
class="cmtt-12">[vorbis_mode_windowtype] </span>and <span
class="cmtt-12">[vorbis_mode_transformtype]</span>.
<span
class="cmtt-12">[vorbis_mode_mapping] </span>must not be greater than the highest number mapping
in use. Any illegal values render the stream undecodable.
- </li>
- <li
- class="enumerate" id="x1-70016x6">save this mode configuration in slot <span
+ </dd><dt class="enumerate-enumitem">
+ f) </dt><dd
+class="enumerate-enumitem">save this mode configuration in slot <span
class="cmtt-12">[i] </span>of the mode configuration array
<span
-class="cmtt-12">[vorbis_mode_configurations]</span>.</li></ol>
- </li>
- <li
- class="enumerate" id="x1-70018x3">read 1 bit as a framing flag. If unset, a framing error occurred and the stream is not
- decodable.</li></ol>
+class="cmtt-12">[vorbis_mode_configurations]</span>.</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">read 1 bit as a framing flag. If unset, a framing error occurred and the stream is not
+ decodable.</dd></dl>
<!--l. 268--><p class="noindent" >After reading mode descriptions, setup header decode is complete.
<!--l. 277--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">4.3 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">4.3
. </span> <a
id="x1-710004.3"></a>Audio packet decode and synthesis</h4>
<!--l. 279--><p class="noindent" >Following the three header packets, all packets in a Vorbis I stream are audio. The first step of
audio packet decode is to read and verify the packet type. <span
<span
class="cmti-12">packet and not attempt decoding it to audio</span>.
<!--l. 286--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.1
. </span> <a
id="x1-720004.3.1"></a>packet type, mode and window decode</h5>
-<!--l. 28
8--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-72002x1">read 1 bit <span
+<!--l. 28
9--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">read 1 bit <span
class="cmtt-12">[packet_type]</span>; check that packet type is 0 (audio)
- </li>
- <li
-
class="enumerate" id="x1-72004x2">read <a
-href="#x1-1170009.2.1">ilog</a>([vorbis˙mode˙count]-1) bits <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+
class="enumerate-enumitem">read <a
+href="#x1-1170009.2.1">ilog</a>([vorbis_mode_count]-1) bits <span
class="cmtt-12">[mode_number]</span>
- </li>
- <li
- class="enumerate" id="x1-72006x3">decode blocksize <span
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">decode blocksize <span
class="cmtt-12">[n] </span>is equal to <span
class="cmtt-12">[blocksize_0] </span>if <span
class="cmtt-12">[vorbis_mode_blockflag] </span>is 0,
else <span
class="cmtt-12">[n] </span>is equal to <span
class="cmtt-12">[blocksize_1]</span>.
- </li>
- <li
- class="enumerate" id="x1-72008x4">perform window selection and setup; this window is used later by the inverse
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">perform window selection and setup; this window is used later by the inverse
MDCT:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-72010x1">if this is a long window (the <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">if this is a long window (the <span
class="cmtt-12">[vorbis_mode_blockflag] </span>flag of this mode is
set):
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-72012x1">read 1 bit for <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">read 1 bit for <span
class="cmtt-12">[previous_window_flag]</span>
- </li>
- <li
- class="enumerate" id="x1-72014x2">read 1 bit for <span
+ </dd><dt class="enumerate-enumitem">
+ ii. </dt><dd
+class="enumerate-enumitem">read 1 bit for <span
class="cmtt-12">[next_window_flag]</span>
- </li>
- <li
- class="enumerate" id="x1-72016x3">if <span
+ </dd><dt class="enumerate-enumitem">
+ iii. </dt><dd
+class="enumerate-enumitem">if <span
class="cmtt-12">[previous_window_flag] </span>is not set, the left half of the window will
be a hybrid window for lapping with a short block. See <a
href="#paragraph.1" >paragraph <a
href="#x1-260001.3.2">Window shape decode (long windows only)<!--tex4ht:ref: vorbis:spec:window --></a>” for an illustration of
overlapping dissimilar windows. Else, the left half window will have normal
long shape.
- </li>
- <li
- class="enumerate" id="x1-72018x4">if <span
+ </dd><dt class="enumerate-enumitem">
+ iv. </dt><dd
+class="enumerate-enumitem">if <span
class="cmtt-12">[next_window_flag] </span>is not set, the right half of the window will be
a hybrid window for lapping with a short block. See <a
href="#x1-260001.3.2">paragraph 1.3.2</a>,
“<a
href="#x1-260001.3.2">Window shape decode (long windows only)<!--tex4ht:ref: vorbis:spec:window --></a>” for an illustration of
overlapping dissimilar windows. Else, the left right window will have normal
- long shape.</li></ol>
- </li>
- <li
- class="enumerate" id="x1-72020x2">if this is a short window, the window is always the same short-window
- shape.</li></ol>
- </li></ol>
+ long shape.</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem">if this is a short window, the window is always the same short-window
+ shape.</dd></dl>
+ </dd></dl>
<!--l. 321--><p class="noindent" >Vorbis windows all use the slope function <span
class="cmmi-12">y </span>= sin(<img
src="Vorbis_I_spec1x.png" alt="π2" class="frac" align="middle"> <span
class="cmmi-12">n</span><span
class="cmsy-10x-x-120">− </span>1, but dissimilar lapping requirements can affect overall shape. Window
generation proceeds as follows:
-<!--l. 32
6--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-72022x1"><span
+<!--l. 32
7--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[window_center] </span>= <span
class="cmtt-12">[n] </span>/ 2
- </li>
- <li
- class="enumerate" id="x1-72024x2">if (<span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">if (<span
class="cmtt-12">[vorbis_mode_blockflag] </span>is set and <span
class="cmtt-12">[previous_window_flag] </span>is not set)
then
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-72026x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_window_start] </span>= <span
class="cmtt-12">[n]</span>/4 - <span
class="cmtt-12">[blocksize_0]</span>/4
- </li>
- <li
- class="enumerate" id="x1-72028x2"><span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_window_end] </span>= <span
class="cmtt-12">[n]</span>/4 + <span
class="cmtt-12">[blocksize_0]</span>/4
- </li>
- <li
- class="enumerate" id="x1-72030x3"><span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_n] </span>= <span
-class="cmtt-12">[blocksize_0]</span>/2</li></ol>
+class="cmtt-12">[blocksize_0]</span>/2</dd></dl>
<!--l. 336--><p class="noindent" >else
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-72032x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_window_start] </span>= 0
- </li>
- <li
- class="enumerate" id="x1-72034x2"><span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_window_end] </span>= <span
class="cmtt-12">[window_center]</span>
- </li>
- <li
- class="enumerate" id="x1-72036x3"><span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[left_n] </span>= <span
-class="cmtt-12">[n]</span>/2</li></ol>
- </li>
- <li
- class="enumerate" id="x1-72038x3">if (<span
+class="cmtt-12">[n]</span>/2</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">if (<span
class="cmtt-12">[vorbis_mode_blockflag] </span>is set and <span
class="cmtt-12">[next_window_flag] </span>is not set) then
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-72040x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_window_start] </span>= <span
class="cmtt-12">[n]*3</span>/4 - <span
class="cmtt-12">[blocksize_0]</span>/4
- </li>
- <li
- class="enumerate" id="x1-72042x2"><span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_window_end] </span>= <span
class="cmtt-12">[n]*3</span>/4 + <span
class="cmtt-12">[blocksize_0]</span>/4
- </li>
- <li
- class="enumerate" id="x1-72044x3"><span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_n] </span>= <span
-class="cmtt-12">[blocksize_0]</span>/2</li></ol>
+class="cmtt-12">[blocksize_0]</span>/2</dd></dl>
<!--l. 352--><p class="noindent" >else
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-72046x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_window_start] </span>= <span
class="cmtt-12">[window_center]</span>
- </li>
- <li
- class="enumerate" id="x1-72048x2"><span
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_window_end] </span>= <span
class="cmtt-12">[n]</span>
- </li>
- <li
- class="enumerate" id="x1-72050x3"><span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[right_n] </span>= <span
-class="cmtt-12">[n]</span>/2</li></ol>
- </li>
- <li
- class="enumerate" id="x1-72052x4">window from range 0 ... <span
+class="cmtt-12">[n]</span>/2</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">window from range 0 ... <span
class="cmtt-12">[left_window_start]</span>-1 inclusive is zero
- </li>
- <li
- class="enumerate" id="x1-72054x5">for <span
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem">for <span
class="cmtt-12">[i] </span>in range <span
class="cmtt-12">[left_window_start] </span>... <span
class="cmtt-12">[left_window_end]</span>-1, window(<span
class="cmsy-10x-x-120">∗</span><img
src="Vorbis_I_spec3x.png" alt="π
2" class="frac" align="middle">) )
- </li>
- <li
- class="enumerate" id="x1-72056x6">window from range <span
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem">window from range <span
class="cmtt-12">[left_window_end] </span>... <span
class="cmtt-12">[right_window_start]</span>-1 inclusive is
one
- </li>
- <li
- class="enumerate" id="x1-72058x7">for <span
+ </dd><dt class="enumerate-enumitem">
+ 7. </dt><dd
+class="enumerate-enumitem">for <span
class="cmtt-12">[i] </span>in range <span
class="cmtt-12">[right_window_start] </span>... <span
class="cmtt-12">[right_window_end]</span>-1, window(<span
2" class="frac" align="middle"> + <img
src="Vorbis_I_spec6x.png" alt="π
2" class="frac" align="middle">) )
- </li>
- <li
- class="enumerate" id="x1-72060x8">window from range <span
+ </dd><dt class="enumerate-enumitem">
+ 8. </dt><dd
+class="enumerate-enumitem">window from range <span
class="cmtt-12">[right_window_start] </span>... <span
-class="cmtt-12">[n]</span>-1 is zero</li></ol>
+class="cmtt-12">[n]</span>-1 is zero</dd></dl>
<!--l. 368--><p class="noindent" >An end-of-packet condition up to this point should be considered an error that discards this
packet from the stream. An end of packet condition past this point is to be considered a possible
nominal occurrence.
<!--l. 375--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.2
. </span> <a
id="x1-730004.3.2"></a>floor curve decode</h5>
<!--l. 377--><p class="noindent" >From this point on, we assume out decode context is using mode number <span
class="cmtt-12">[mode_number]</span>
<!--l. 386--><p class="noindent" >For each floor <span
class="cmtt-12">[i] </span>of <span
class="cmtt-12">[audio_channels]</span>
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-73002x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[submap_number] </span>= element <span
-class="cmtt-12">[i] </span>of vector [vorbis˙mapping˙mux]
- </li>
- <li
- class="enumerate" id="x1-73004x2"><span
+class="cmtt-12">[i] </span>of vector [vorbis_mapping_mux]
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[floor_number] </span>= element <span
-class="cmtt-12">[submap_number] </span>of vector [vorbis˙submap˙floor]
- </li>
- <li
- class="enumerate" id="x1-73006x3">if the floor type of this floor (vector
+class="cmtt-12">[submap_number] </span>of vector [vorbis_submap_floor]
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">if the floor type of this floor (vector
<span
class="cmtt-12">[vorbis_floor_types] </span>element <span
class="cmtt-12">[floor_number]</span>) is zero then decode the floor for
class="cmtt-12">[i] </span>according to the <a
href="#x1-930006.2.2">subsubsection 6.2.2</a>, “<a
href="#x1-930006.2.2">packet decode<!--tex4ht:ref: vorbis:spec:floor0-decode --></a>”
- </li>
- <li
- class="enumerate" id="x1-73008x4">if the type of this floor is one then decode the floor for channel <span
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">if the type of this floor is one then decode the floor for channel <span
class="cmtt-12">[i] </span>according to the
<a
-href="#x1-1000007.2.
2">paragraph 7.2.2</a>, “<a
-href="#x1-1000007.2.2">packet decode<!--tex4ht:ref: vorbis:spec:floor1-decode --></a>”
- </li>
- <li
- class="enumerate" id="x1-73010x5">save the needed decoded floor information for channel for later synthesis
- </li>
- <li
- class="enumerate" id="x1-73012x6">if the decoded floor returned ’unused’, set vector <span
+href="#x1-1000007.2.
3">subsubsection 7.2.3</a>, “<a
+href="#x1-1000007.2.3">packet decode<!--tex4ht:ref: vorbis:spec:floor1-decode --></a>”
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem">save the needed decoded floor information for channel for later synthesis
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem">if the decoded floor returned ’unused’, set vector <span
class="cmtt-12">[no_residue] </span>element <span
class="cmtt-12">[i] </span>to true,
else set vector <span
class="cmtt-12">[no_residue] </span>element <span
-class="cmtt-12">[i] </span>to false</li></ol>
+class="cmtt-12">[i] </span>to false</dd></dl>
<!--l. 406--><p class="noindent" >An end-of-packet condition during floor decode shall result in packet decode zeroing all channel
output vectors and skipping to the add/overlap output stage.
<!--l. 412--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.3
. </span> <a
id="x1-740004.3.3"></a>nonzero vector propagate</h5>
<!--l. 414--><p class="noindent" >A possible result of floor decode is that a specific vector is marked ’unused’ which indicates that
that final output vector is all-zero values (and the floor is zero). The residue for that vector is not
<!--l. 421--><p class="noindent" >for each <span
class="cmtt-12">[i] </span>from 0 ... <span
class="cmtt-12">[vorbis_mapping_coupling_steps]</span>-1
-<!--l. 42
3--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-74002x1">if either <span
+<!--l. 42
4--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">if either <span
class="cmtt-12">[no_residue] </span>entry for channel (<span
class="cmtt-12">[vorbis_mapping_magnitude] </span>element
<span
class="cmtt-12">[vorbis_mapping_angle] </span>element <span
class="cmtt-12">[i]</span>) are set to false, then both
must be set to false. Note that an ’unused’ floor has no decoded floor information; it
- is important that this is remembered at floor curve synthesis time.</li></ol>
+ is important that this is remembered at floor curve synthesis time.</dd></dl>
<!--l. 436--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.4
. </span> <a
id="x1-750004.3.4"></a>residue decode</h5>
<!--l. 438--><p class="noindent" >Unlike floors, which are decoded in channel order, the residue vectors are decoded in submap
order.
<!--l. 441--><p class="noindent" >for each submap <span
class="cmtt-12">[i] </span>in order from 0 ... <span
class="cmtt-12">[vorbis_mapping_submaps]</span>-1
-<!--l. 44
3--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-75002x1"><span
+<!--l. 44
4--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[ch] </span>= 0
- </li>
- <li
- class="enumerate" id="x1-75004x2">for each channel <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">for each channel <span
class="cmtt-12">[j] </span>in order from 0 ... <span
class="cmtt-12">[audio_channels] </span>- 1
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-75006x1">if channel <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">if channel <span
class="cmtt-12">[j] </span>in submap <span
class="cmtt-12">[i] </span>(vector <span
class="cmtt-12">[vorbis_mapping_mux] </span>element <span
class="cmtt-12">[j] </span>is equal to
<span
class="cmtt-12">[i]</span>)
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-75008x1">if vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">if vector <span
class="cmtt-12">[no_residue] </span>element <span
class="cmtt-12">[j] </span>is true
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-75010x1">vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">vector <span
class="cmtt-12">[do_not_decode_flag] </span>element <span
-class="cmtt-12">[ch] </span>is set</li></ol>
+class="cmtt-12">[ch] </span>is set</dd></dl>
<!--l. 453--><p class="noindent" >else
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-75012x1">vector <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem">vector <span
class="cmtt-12">[do_not_decode_flag] </span>element <span
-class="cmtt-12">[ch] </span>is unset</li></ol>
- </li>
- <li
- class="enumerate" id="x1-75014x2">increment <span
-class="cmtt-12">[ch]</span></li></ol>
+class="cmtt-12">[ch] </span>is unset</dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ ii. </dt><dd
+class="enumerate-enumitem">increment <span
+class="cmtt-12">[ch]</span></dd></dl>
- </li></ol>
- </li>
- <li
- class="enumerate" id="x1-75016x3"><span
+ </dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[residue_number] </span>= vector <span
class="cmtt-12">[vorbis_mapping_submap_residue] </span>element <span
class="cmtt-12">[i]</span>
- </li>
- <li
- class="enumerate" id="x1-75018x4"><span
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[residue_type] </span>= vector <span
class="cmtt-12">[vorbis_residue_types] </span>element <span
class="cmtt-12">[residue_number]</span>
- </li>
- <li
- class="enumerate" id="x1-75020x5">decode <span
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem">decode <span
class="cmtt-12">[ch] </span>vectors using residue <span
class="cmtt-12">[residue_number]</span>, according to type <span
class="cmtt-12">[residue_type]</span>,
class="cmtt-12">[do_not_decode_flag] </span>to indicate which vectors in the bundle should
not be decoded. Correct per-vector decode length is <span
class="cmtt-12">[n]</span>/2.
- </li>
- <li
- class="enumerate" id="x1-75022x6"><span
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[ch] </span>= 0
- </li>
- <li
- class="enumerate" id="x1-75024x7">for each channel <span
+ </dd><dt class="enumerate-enumitem">
+ 7. </dt><dd
+class="enumerate-enumitem">for each channel <span
class="cmtt-12">[j] </span>in order from 0 ... <span
class="cmtt-12">[audio_channels]</span>
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-75026x1">if channel <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">if channel <span
class="cmtt-12">[j] </span>is in submap <span
class="cmtt-12">[i] </span>(vector <span
class="cmtt-12">[vorbis_mapping_mux] </span>element <span
class="cmtt-12">[j] </span>is equal
to <span
class="cmtt-12">[i]</span>)
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-75028x1">residue vector for channel <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">residue vector for channel <span
class="cmtt-12">[j] </span>is set to decoded residue vector <span
class="cmtt-12">[ch]</span>
- </li>
- <li
- class="enumerate" id="x1-75030x2">increment <span
-class="cmtt-12">[ch]</span></li></ol>
- </li></ol>
- </li></ol>
+ </dd><dt class="enumerate-enumitem">
+ ii. </dt><dd
+class="enumerate-enumitem">increment <span
+class="cmtt-12">[ch]</span></dd></dl>
+ </dd></dl>
+ </dd></dl>
<!--l. 480--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.5 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.5
. </span> <a
id="x1-760004.3.5"></a>inverse coupling</h5>
<!--l. 482--><p class="noindent" >for each <span
class="cmtt-12">[i] </span>from <span
class="cmtt-12">[vorbis_mapping_coupling_steps]</span>-1 descending to 0
-<!--l. 48
4--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-76002x1"><span
+<!--l. 48
5--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[magnitude_vector] </span>= the residue vector for channel (vector
<span
class="cmtt-12">[vorbis_mapping_magnitude] </span>element <span
class="cmtt-12">[i]</span>)
- </li>
- <li
- class="enumerate" id="x1-76004x2"><span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[angle_vector] </span>= the residue vector for channel (vector <span
class="cmtt-12">[vorbis_mapping_angle]</span>
element <span
class="cmtt-12">[i]</span>)
- </li>
- <li
- class="enumerate" id="x1-76006x3">for each scalar value <span
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">for each scalar value <span
class="cmtt-12">[M] </span>in vector <span
class="cmtt-12">[magnitude_vector] </span>and the corresponding scalar value
<span
class="cmtt-12">[A] </span>in vector <span
class="cmtt-12">[angle_vector]</span>:
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-76008x1">if (<span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">if (<span
class="cmtt-12">[M] </span>is greater than zero)
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-76010x1">if (<span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">if (<span
class="cmtt-12">[A] </span>is greater than zero)
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-76012x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_M] </span>= <span
class="cmtt-12">[M]</span>
- </li>
- <li
- class="enumerate" id="x1-76014x2"><span
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_A] </span>= <span
class="cmtt-12">[M]</span>-<span
-class="cmtt-12">[A]</span></li></ol>
+class="cmtt-12">[A]</span></dd></dl>
<!--l. 498--><p class="noindent" >else
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-76016x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_A] </span>= <span
class="cmtt-12">[M]</span>
- </li>
- <li
- class="enumerate" id="x1-76018x2"><span
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_M] </span>= <span
class="cmtt-12">[M]</span>+<span
-class="cmtt-12">[A]</span></li></ol>
- </li></ol>
+class="cmtt-12">[A]</span></dd></dl>
+ </dd></dl>
<!--l. 505--><p class="noindent" >else
- <ol class="enumerate3" >
- <li
- class="enumerate" id="x1-76020x1">if (<span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ i. </dt><dd
+class="enumerate-enumitem">if (<span
class="cmtt-12">[A] </span>is greater than zero)
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-76022x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_M] </span>= <span
class="cmtt-12">[M]</span>
- </li>
- <li
- class="enumerate" id="x1-76024x2"><span
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_A] </span>= <span
class="cmtt-12">[M]</span>+<span
-class="cmtt-12">[A]</span></li></ol>
+class="cmtt-12">[A]</span></dd></dl>
<!--l. 512--><p class="noindent" >else
- <ol class="enumerate4" >
- <li
- class="enumerate" id="x1-76026x1"><span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ A. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_A] </span>= <span
class="cmtt-12">[M]</span>
- </li>
- <li
- class="enumerate" id="x1-76028x2"><span
+ </dd><dt class="enumerate-enumitem">
+ B. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[new_M] </span>= <span
class="cmtt-12">[M]</span>-<span
-class="cmtt-12">[A]</span></li></ol>
- </li></ol>
- </li>
- <li
- class="enumerate" id="x1-76030x2">set scalar value <span
+class="cmtt-12">[A]</span></dd></dl>
+ </dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem">set scalar value <span
class="cmtt-12">[M] </span>in vector <span
class="cmtt-12">[magnitude_vector] </span>to <span
class="cmtt-12">[new_M]</span>
- </li>
- <li
- class="enumerate" id="x1-76032x3">set scalar value <span
+ </dd><dt class="enumerate-enumitem">
+ c) </dt><dd
+class="enumerate-enumitem">set scalar value <span
class="cmtt-12">[A] </span>in vector <span
class="cmtt-12">[angle_vector] </span>to <span
-class="cmtt-12">[new_A]</span></li></ol>
- </li></ol>
+class="cmtt-12">[new_A]</span></dd></dl>
+ </dd></dl>
<!--l. 529--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.6 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.6
. </span> <a
id="x1-770004.3.6"></a>dot product</h5>
<!--l. 531--><p class="noindent" >For each channel, synthesize the floor curve from the decoded floor information, according to
packet type. Note that the vector synthesis length for floor computation is <span
achieved using large (64 bit or larger) integers, or implementing a movable binary point
representation.
<!--l. 567--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.7 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.7
. </span> <a
id="x1-780004.3.7"></a>inverse MDCT</h5>
<!--l. 569--><p class="noindent" >Convert the audio spectrum vector of each channel back into time domain PCM audio via an
href="#XSporer/Brandenburg/Edler">1</a>]</span>. The window function used for the MDCT is the function described
earlier.
<!--l. 576--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.8 </span> <a
- id="x1-790004.3.8"></a>overlap˙add</h5>
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.8
. </span> <a
+ id="x1-790004.3.8"></a>overlap_add</h5>
<!--l. 578--><p class="noindent" >Windowed MDCT output is overlapped and added with the right hand data of the previous
window such that the 3/4 point of the previous window is aligned with the 1/4 point of the
current window (as illustrated in <a
id="x1-79002r1"></a><span
class="cmr-6">1</span><span
class="cmtt-8"> </span><span
-class="cmtt-8"> window_blocksize(previous_window)/4+window_blocksize(current_window)/4</span>
+class="cmtt-8"> window\_blocksize(previous\_window)/4+window\_blocksize(current\_window)/4</span>
</div>
<!--l. 596--><p class="noindent" >from the center (element windowsize/2) of the previous window to the center (element
windowsize/2-1, inclusive) of the current window.
encoder accounts for this priming when calculating PCM offsets; after the first frame, the proper
PCM output offset is ’0’ (as no data has been returned yet).
<!--l. 606--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">4.3.9 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">4.3.9
. </span> <a
id="x1-800004.3.9"></a>output channel order</h5>
<!--l. 608--><p class="noindent" >Vorbis I specifies only a channel mapping type 0. In mapping type 0, channel mapping is
implicitly defined as follows for standard audio applications. As of revision 16781 (20100113), the
<!--l. 614--><p class="noindent" >These channel orderings refer to order within the encoded stream. It is naturally possible for a
decoder to produce output with channels in any order. Any such decoder should explicitly
document channel reordering behavior.
-<!--l. 6
19--><p class="noindent" >
+<!--l. 6
20--><p class="noindent" >
<dl class="description"><dt class="description">
<span
class="cmssbx-10x-x-120">one channel</span> </dt><dd
-<h3 class="sectionHead"><span class="titlemark">5 </span> <a
+<h3 class="sectionHead"><span class="titlemark">5
. </span> <a
id="x1-810005"></a>comment field and header specification</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">5.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">5.1
. </span> <a
id="x1-820005.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >The Vorbis text comment header is the second (of three) header packets that begin a Vorbis
bitstream. It is meant for short text comments, not arbitrary metadata; arbitrary metadata
class="cmti-12">“I’m Still Around”</span>, opening
for Moxy Früvous, 1997.</div>
<!--l. 29--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">5.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">5.2
. </span> <a
id="x1-830005.2"></a>Comment encoding</h4>
<!--l. 31--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">5.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">5.2.1
. </span> <a
id="x1-840005.2.1"></a>Structure</h5>
<!--l. 33--><p class="noindent" >The comment header is logically a list of eight-bit-clean vectors; the number of vectors is
bounded to 2<sup><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 1)</span><span
-class="cmtt-8"> [vendor_length]</span><span
+class="cmtt-8"> [vendor\_length]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> an</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
-class="cmtt-8"> [vendor_string]</span><span
+class="cmtt-8"> [vendor\_string]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> a</span><span
class="cmtt-8"> UTF-8</span><span
class="cmtt-8"> vector</span><span
class="cmtt-8"> as</span><span
-class="cmtt-8"> [vendor_length]</span><span
+class="cmtt-8"> [vendor\_length]</span><span
class="cmtt-8"> octets</span>
<br class="fancyvrb" /><a
id="x1-84006r3"></a><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
-class="cmtt-8"> [user_comment_list_length]</span><span
+class="cmtt-8"> [user\_comment\_list\_length]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> an</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
class="cmtt-8"> iterate</span><span
-class="cmtt-8"> [user_comment_list_length]</span><span
+class="cmtt-8"> [user\_comment\_list\_length]</span><span
class="cmtt-8"> times</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 7)</span><span
-class="cmtt-8"> [framing_bit]</span><span
+class="cmtt-8"> [framing\_bit]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> a</span><span
class="cmtt-8"> 8)</span><span
class="cmtt-8"> if</span><span
class="cmtt-8"> (</span><span
-class="cmtt-8"> [framing_bit]</span><span
+class="cmtt-8"> [framing\_bit]</span><span
class="cmtt-8"> unset</span><span
class="cmtt-8"> or</span><span
class="cmtt-8"> end-of-packet</span><span
class="cmtt-8"> done.</span>
</div>
<!--l. 64--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">5.2.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">5.2.2
. </span> <a
id="x1-850005.2.2"></a>Content vector format</h5>
<!--l. 66--><p class="noindent" >The comment vectors are structured similarly to a UNIX environment variable. That is,
comment fields consist of a field name and a corresponding value and look like:
Below is a proposed, minimal list of standard field names with a description of intended use. No
single or group of field names is mandatory; a comment header may contain one, all or none of
the names in this list.
-<!--l. 9
8--><p class="noindent" >
+<!--l. 9
9--><p class="noindent" >
<dl class="description"><dt class="description">
<span
class="cmssbx-10x-x-120">TITLE</span> </dt><dd
a license such as a Creative
Commons license (”www.creativecommons.org/blahblah/license.html”) or the EFF
Open Audio License (’distributed under the terms of the Open Audio License. see
- http://www.eff.org/IP/Open˙licenses/eff˙oal.html for details’), etc.
+ http://www.eff.org/IP/Open_licenses/eff_oal.html for details’), etc.
</dd><dt class="description">
<span
class="cmssbx-10x-x-120">ORGANIZATION</span> </dt><dd
</div>
</div>
<!--l. 197--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">5.2.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">5.2.3
. </span> <a
id="x1-880005.2.3"></a>Encoding</h5>
<!--l. 199--><p class="noindent" >The comment header comprises the entirety of the second bitstream header packet. Unlike the
first bitstream header packet, it is not generally the only packet on the second page and may not
<!--l. 207--><p class="noindent" >The comment header is encoded as follows (as per Ogg’s standard bitstream mapping which
renders least-significant-bit of the word to be coded into the least significant available bit of the
current bitstream octet first):
-<!--l. 21
2--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-88002x1">Vendor string length (32 bit unsigned quantity specifying number of octets)
- </li>
- <li
- class="enumerate" id="x1-88004x2">Vendor string ([vendor string length] octets coded from beginning of string to end of
+<!--l. 21
3--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">Vendor string length (32 bit unsigned quantity specifying number of octets)
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">Vendor string ([vendor string length] octets coded from beginning of string to end of
string, not null terminated)
- </li>
- <li
- class="enumerate" id="x1-88006x3">Number of comment fields (32 bit unsigned quantity specifying number of fields)
- </li>
- <li
- class="enumerate" id="x1-88008x4">Comment field 0 length (if [Number of comment fields] <span
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">Number of comment fields (32 bit unsigned quantity specifying number of fields)
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">Comment field 0 length (if [Number of comment fields] <span
class="cmmi-12">> </span>0; 32 bit unsigned quantity
specifying number of octets)
- </li>
- <li
- class="enumerate" id="x1-88010x5">Comment field 0 ([Comment field 0 length] octets coded from beginning of string to
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem">Comment field 0 ([Comment field 0 length] octets coded from beginning of string to
end of string, not null terminated)
- </li>
- <li
- class="enumerate" id="x1-88012x6">Comment field 1 length (if [Number of comment fields] <span
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem">Comment field 1 length (if [Number of comment fields] <span
class="cmmi-12">> </span>1...)...
- </li></ol>
+ </dd></dl>
<!--l. 234--><p class="noindent" >This is actually somewhat easier to describe in code; implementation of the above can be found
in <span
class="cmtt-12">vorbis/lib/info.c</span>, <span
-<h3 class="sectionHead"><span class="titlemark">6 </span> <a
+<h3 class="sectionHead"><span class="titlemark">6
. </span> <a
id="x1-890006"></a>Floor type 0 setup and decode</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">6.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">6.1
. </span> <a
id="x1-900006.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >Vorbis floor type zero uses Line Spectral Pair (LSP, also alternately known as Line Spectral
Frequency or LSF) representation to encode a smooth spectral envelope curve as the frequency
impulse response filter as would be used in linear predictive coding; LSP representation may be
converted to LPC representation and vice-versa.
<!--l. 18--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">6.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">6.2
. </span> <a
id="x1-910006.2"></a>Floor 0 format</h4>
<!--l. 20--><p class="noindent" >Floor zero configuration consists of six integer fields and a list of VQ codebooks for use in
coding/decoding the LSP filter coefficient values used by each frame.
<!--l. 24--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">6.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">6.2.1
. </span> <a
id="x1-920006.2.1"></a>header decode</h5>
<!--l. 26--><p class="noindent" >Configuration information for instances of floor zero decodes from the codec setup header (third
packet). configuration decode proceeds as follows:
codebook number for this bitstream is an error condition that also renders the stream
undecodable.
<!--l. 48--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">6.2.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">6.2.2
. </span> <a
id="x1-930006.2.2"></a>packet decode</h5>
<!--l. 50--><p class="noindent" >Extracting a floor0 curve from an audio packet consists of first decoding the curve
amplitude and <span
be taken not to allow a buffer overflow in decode. The extra values are not used and
may be ignored or discarded.</li></ul>
<!--l. 104--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">6.2.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">6.2.3
. </span> <a
id="x1-940006.2.3"></a>curve computation</h5>
<!--l. 106--><p class="noindent" >Given an <span
class="cmtt-12">[amplitude] </span>integer and <span
-class="cmtt-12">[coefficients] </span>vector from packet decode as well
-as the [floor0˙order], [floor0˙rate], [floor0˙bark˙map˙size], [floor0˙amplitude˙bits] and
-[floor0˙amplitude˙offset] values from floor setup, and an output vector size <span
+class="cmtt-12">[coefficients] </span>vector from packet decode as well as
+the [floor0_order], [floor0_rate], [floor0_bark_map_size], [floor0_amplitude_bits] and
+[floor0_amplitude_offset] values from floor setup, and an output vector size <span
class="cmtt-12">[n] </span>specified by the
decode process, we compute a floor output vector.
<!--l. 113--><p class="noindent" >If the value <span
<center class="par-math-display" >
<img
src="Vorbis_I_spec7x.png" alt=" {
- min (floor0xbarkxmapxsize − 1,foobar ) for i ∈ [0,n − 1 ]
+ min (floor0_bark_map_size − 1,foobar ) for i ∈ [0,n − 1 ]
mapi = − 1 for i = n
" class="par-math-display" ></center>
<!--l. 128--><p class="nopar" >
<center class="par-math-display" >
<img
src="Vorbis_I_spec8x.png" alt=" ⌊ ⌋
- (floor0xrate ⋅ i) floor0xbarkxmapxsize
-foobar = bark -------2n------- ⋅-bark(.5 ⋅ floor0xrate-)
+ (floor0_rate ⋅ i) floor0_bark_map_size
+foobar = bark -------2n------- ⋅-bark(.5 ⋅ floor0_rate-)
" class="par-math-display" ></center>
LSP curve <span
class="cmtt-12">[output] </span>on a log (dB) amplitude scale, mapping it to linear amplitude in the last
step:
-<!--l. 15
0--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-94002x1"><span
+<!--l. 15
1--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[i] </span>= 0
- </li>
- <li
- class="enumerate" id="x1-94004x2"><span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[</span><span
class="cmmi-12">ω</span><span
class="cmtt-12">] </span>= <span
class="cmmi-12">π </span>* map element <span
class="cmtt-12">[i] </span>/ <span
class="cmtt-12">[floor0_bark_map_size]</span>
- </li>
- <li
- class="enumerate" id="x1-94006x3">if ( <span
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">if ( <span
class="cmtt-12">[floor0_order] </span>is odd )
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-94008x1">calculate <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ a) </dt><dd
+class="enumerate-enumitem">calculate <span
class="cmtt-12">[p] </span>and <span
class="cmtt-12">[q] </span>according to: <div class="eqnarray">
<center class="math-display" >
<img
-src="Vorbis_I_spec10x.png" alt=" floor0xorder−3
+src="Vorbis_I_spec10x.png" alt=" floor0_order−3
2 ∏2 2
p = (1 − cos ω) 4(cos([coefficients ]2j+1) − cosω )
- j=0
- floor0x∏or2der−1
-q = 1- 4(cos([coefficients ]2j) − cosω )2
+ floor0_order−1 j=0
+ 1 ----∏2----
+q = -- 4(cos([coefficients ]2j) − cosω )2
4 j=0
" class="math-display" ></center>
</div>
- </li></ol>
+ </dd></dl>
<!--l. 162--><p class="noindent" >else <span
class="cmtt-12">[floor0_order] </span>is even
- <ol class="enumerate2" >
- <li
- class="enumerate" id="x1-94011x1">calculate <span
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ b) </dt><dd
+class="enumerate-enumitem">calculate <span
class="cmtt-12">[p] </span>and <span
class="cmtt-12">[q] </span>according to: <div class="eqnarray">
<center class="math-display" >
<img
-src="Vorbis_I_spec11x.png" alt=" floor0xorder−2
- (1 − cos2ω) ∏2 2
-p = -----2------ 4(cos([coefficients ]2j+1) − cosω )
- j=0
- 2 floor0xor2der−2
-q = (1 +-cos-ω)- ∏ 4(cos([coefficients ] ) − cosω )2
- 2 j=0 2j
+src="Vorbis_I_spec11x.png" alt=" floor0_order−2
+ (1-−-cosω-) ∏2 2
+p = 2 4(cos([coefficients ]2j+1) − cosω)
+ j=0
+ floor0_∏o2rder−-2
+q = (1-+-cosω-) 4(cos([coefficients ]2j) − cos ω)2
+ 2 j=0
" class="math-display" ></center>
</div>
- </li></ol>
- </li>
- <li
- class="enumerate" id="x1-94014x4">calculate <span
+ </dd></dl>
+ </dd><dt class="enumerate-enumitem">
+ 4. </dt><dd
+class="enumerate-enumitem">calculate <span
class="cmtt-12">[linear_floor_value] </span>according to:
<center class="math-display" >
<img
src="Vorbis_I_spec12x.png" alt=" ( ( ))
- amplitude---⋅ floor0xamplitutexoffset---
-exp .11512925 (2floor0xamplitudexbits − 1)√ p + q − floor0xamplitudexoffset
+exp .11512925 amplitude---⋅ floor0_amplitute_√offset---− floor0_amplitude_offset
+ (2floor0_amplitude_bits − 1) p + q
" class="math-display" ></center>
<!--l. 177--><p class="nopar" >
- </li>
- <li
- class="enumerate" id="x1-94016x5"><span
+ </dd><dt class="enumerate-enumitem">
+ 5. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[iteration_condition] </span>= map element <span
class="cmtt-12">[i]</span>
- </li>
- <li
- class="enumerate" id="x1-94018x6"><span
+ </dd><dt class="enumerate-enumitem">
+ 6. </dt><dd
+class="enumerate-enumitem"><span
class="cmtt-12">[output] </span>element <span
class="cmtt-12">[i] </span>= <span
class="cmtt-12">[linear_floor_value]</span>
- </li>
- <li
- class="enumerate" id="x1-94020x7">increment <span
+ </dd><dt class="enumerate-enumitem">
+ 7. </dt><dd
+class="enumerate-enumitem">increment <span
class="cmtt-12">[i]</span>
- </li>
- <li
- class="enumerate" id="x1-94022x8">if ( map element <span
+ </dd><dt class="enumerate-enumitem">
+ 8. </dt><dd
+class="enumerate-enumitem">if ( map element <span
class="cmtt-12">[i] </span>is equal to <span
class="cmtt-12">[iteration_condition] </span>) continue at step
5
- </li>
- <li
- class="enumerate" id="x1-94024x9">if ( <span
+ </dd><dt class="enumerate-enumitem">
+ 9. </dt><dd
+class="enumerate-enumitem">if ( <span
class="cmtt-12">[i] </span>is less than <span
class="cmtt-12">[n] </span>) continue at step 2
- </li>
- <li
- class="enumerate" id="x1-94026x10">done</li></ol>
+ </dd><dt class="enumerate-enumitem">
+ 10. </dt><dd
+class="enumerate-enumitem">done</dd></dl>
-<h3 class="sectionHead"><span class="titlemark">7 </span> <a
+<h3 class="sectionHead"><span class="titlemark">7
. </span> <a
id="x1-950007"></a>Floor type 1 setup and decode</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">7.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">7.1
. </span> <a
id="x1-960007.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >Vorbis floor type one uses a piecewise straight-line representation to encode a spectral envelope
curve. The representation plots this curve mechanically on a linear frequency axis and a
logarithmic (dB) amplitude axis. The integer plotting algorithm used is similar to Bresenham’s
algorithm.
<!--l. 16--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">7.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">7.2
. </span> <a
id="x1-970007.2"></a>Floor 1 format</h4>
<!--l. 18--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">7.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">7.2.1
. </span> <a
id="x1-980007.2.1"></a>model</h5>
<!--l. 20--><p class="noindent" >Floor type one represents a spectral curve as a series of line segments. Synthesis constructs a
floor curve using iterative prediction in a process roughly equivalent to the following simplified
into two steps with modifications to the above algorithm to eliminate noise accumulation
through integer roundoff/truncation.
<!--l. 94--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">7.2.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">7.2.2
. </span> <a
id="x1-990007.2.2"></a>header decode</h5>
<!--l. 96--><p class="noindent" >A list of floor X values is stored in the packet header in interleaved format (used in list order
during packet decode and synthesis). This list is split into partitions, and each partition is
class="cmtt-12">[floor1_class_masterbooks] </span>or
<span
class="cmtt-12">[floor1_subclass_books] </span>scalar element greater than the highest numbered codebook
-configured in this stream is an error condition that renders the stream undecodable. All vector
-[floor1˙x˙list] element values must be unique within the vector; a non-unique value renders the
-stream undecodable.
-<!--l. 167--><p class="noindent" ><span class="paragraphHead"><a
- id="x1-1000007.2.2"></a><span
-class="cmbx-12">packet decode</span></span>
+configured in this stream is an error condition that renders the stream undecodable. Vector
+[floor1_x_list] is limited to a maximum length of 65 elements; a setup indicating more than 65
+total elements (including elements 0 and 1 set prior to the read loop) renders the stream
+undecodable. All vector [floor1_x_list] element values must be unique within the vector; a
+non-unique value renders the stream undecodable.
-Packet decode begins by checking the <span
+<!--l. 170--><p class="noindent" >
+<h5 class="subsubsectionHead"><span class="titlemark">7.2.3. </span> <a
+ id="x1-1000007.2.3"></a>packet decode</h5>
+<!--l. 172--><p class="noindent" >Packet decode begins by checking the <span
class="cmtt-12">[nonzero] </span>flag:
-<!--l. 17
1--><p class="noindent" >
+<!--l. 17
4--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb29">
<a
id="x1-100002r1"></a><span
class="cmtt-8"> as</span><span
class="cmtt-8"> boolean</span>
</div>
-<!--l. 17
5--><p class="noindent" >If <span
+<!--l. 17
8--><p class="noindent" >If <span
class="cmtt-12">[nonzero] </span>is unset, that indicates this channel contained no audio energy in this frame.
Decode immediately returns a status indicating this floor curve (and thus this channel) is unused
this frame. (A return status of ’unused’ is different from decoding a floor that has all
points set to minimum representation amplitude, which happens to be approximately
-140dB).
-<!--l. 18
3--><p class="noindent" >Assuming <span
+<!--l. 18
6--><p class="noindent" >Assuming <span
class="cmtt-12">[nonzero] </span>is set, decode proceeds as follows:
-<!--l. 18
5--><p class="noindent" >
+<!--l. 18
8--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb30">
<a
id="x1-100004r1"></a><span
class="cmtt-8"> [offset]</span><span
class="cmtt-8"> +</span><span
class="cmtt-8"> [cdim]</span>
+
+
+
<br class="fancyvrb" /><a
id="x1-100072r35"></a><span
class="cmr-6">35</span><span
class="cmtt-8"> 20)</span><span
class="cmtt-8"> done</span>
</div>
-
-
-
-<!--l. 226--><p class="noindent" >An end-of-packet condition during curve decode should be considered a nominal occurrence; if
+<!--l. 229--><p class="noindent" >An end-of-packet condition during curve decode should be considered a nominal occurrence; if
end-of-packet is reached during any read operation above, floor decode is to return ’unused’
status as if the <span
class="cmtt-12">[nonzero] </span>flag had been unset at the beginning of decode.
-<!--l. 23
2--><p class="noindent" >Vector <span
+<!--l. 23
5--><p class="noindent" >Vector <span
class="cmtt-12">[floor1_Y] </span>contains the values from packet decode needed for floor 1 synthesis.
-<!--l. 237--><p class="noindent" ><span class="paragraphHead"><a
- id="x1-1010007.2.2"></a><span
-class="cmbx-12">curve computation</span></span>
-Curve computation is split into two logical steps; the first step derives final Y amplitude values
+<!--l. 240--><p class="noindent" >
+<h5 class="subsubsectionHead"><span class="titlemark">7.2.4. </span> <a
+ id="x1-1010007.2.4"></a>curve computation</h5>
+<!--l. 242--><p class="noindent" >Curve computation is split into two logical steps; the first step derives final Y amplitude values
from the encoded, wrapped difference values taken from the bitstream. The second step
plots the curve lines. Also, although zero-difference values are used in the iterative
prediction to find final Y values, these points are conditionally skipped during final
line computation in step two. Skipping zero-difference values allows a smoother line
fit.
-<!--l. 2
47--><p class="noindent" >Although some aspects of the below algorithm look like inconsequential optimizations,
+<!--l. 2
50--><p class="noindent" >Although some aspects of the below algorithm look like inconsequential optimizations,
implementors are warned to follow the details closely. Deviation from implementing a strictly
equivalent algorithm can result in serious decoding errors.
-<!--l. 252--><p class="noindent" >
+<!--l. 255--><p class="noindent" ><span
+class="cmti-12">Additional note: </span>Although <span
+class="cmtt-12">[floor1_final_Y] </span>values in the prediction loop and at the end of
+step 1 are inherently limited by the prediction algorithm to [0, <span
+class="cmtt-12">[range]</span>), it is possible to abuse
+the setup and codebook machinery to produce negative or over-range results. We suggest that
+decoder implementations guard the values in vector <span
+class="cmtt-12">[floor1_final_Y] </span>by clamping each
+element to [0, <span
+class="cmtt-12">[range]</span>) after step 1. Variants of this suggestion are acceptable as valid floor1
+setups cannot produce out of range values.
+<!--l. 266--><p class="noindent" >
<dl class="description"><dt class="description">
<span
class="cmssbx-10x-x-120">step 1: amplitude value synthesis</span> </dt><dd
class="description">
- <!--l. 2
55--><p class="noindent" >Unwrap the always-positive-or-zero values read from the packet into +/- difference
+ <!--l. 2
68--><p class="noindent" >Unwrap the always-positive-or-zero values read from the packet into +/- difference
values, then apply to line prediction.
- <!--l. 2
58--><p class="noindent" >
+ <!--l. 2
71--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb31">
+
+
+
<a
id="x1-101002r1"></a><span
class="cmr-6">1</span><span
class="cmtt-8"> [highroom]</span><span
class="cmtt-8"> *</span><span
class="cmtt-8"> 2</span>
-
-
-
<br class="fancyvrb" /><a
id="x1-101046r23"></a><span
class="cmr-6">23</span><span
id="x1-101098r49"></a><span
class="cmr-6">49</span><span
class="cmtt-8"> </span><span
-class="cmtt-8">  </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
+class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 24)</span><span
class="cmtt-8"> if</span><span
class="cmtt-8"> [i]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> unset</span>
+
+
+
<br class="fancyvrb" /><a
id="x1-101132r66"></a><span
class="cmr-6">66</span><span
<span
class="cmssbx-10x-x-120">step 2: curve synthesis</span> </dt><dd
class="description">
- <!--l. 3
38--><p class="noindent" >Curve synthesis generates a return vector <span
+ <!--l. 3
51--><p class="noindent" >Curve synthesis generates a return vector <span
class="cmtt-12">[floor] </span>of length <span
class="cmtt-12">[n] </span>(where <span
class="cmtt-12">[n] </span>is provided by
class="cmtt-12">[floor1_X_list]</span>, <span
class="cmtt-12">[floor1_final_Y] </span>and <span
class="cmtt-12">[floor1_step2_flag] </span>vectors, as well as
- [floor1˙multiplier] and [floor1˙values] values.
-
-
-
- <!--l. 345--><p class="noindent" >Decode begins by sorting the scalars from vectors <span
+ [floor1_multiplier] and [floor1_values] values.
+ <!--l. 358--><p class="noindent" >Decode begins by sorting the scalars from vectors <span
class="cmtt-12">[floor1_X_list]</span>, <span
class="cmtt-12">[floor1_final_Y] </span>and
<span
<span
class="cmtt-12">[floor1_X_list]</span>. That is, sort the values of <span
class="cmtt-12">[floor1_X_list] </span>and then apply the same
- permutation to elements of the other two vectors so that the X, Y and step2˙flag values still
- match.
- <!--l. 3
55--><p class="noindent" >Then compute the final curve in one pass:
- <!--l. 3
57--><p class="noindent" >
+ permutation to elements of the other two vectors so that the X, Y and step2_flag values
+ still match.
+ <!--l. 3
68--><p class="noindent" >Then compute the final curve in one pass:
+ <!--l. 3
70--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb32">
<a
id="x1-101148r1"></a><span
class="cmr-6">27</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
+
+
+
<br class="fancyvrb" /><a
id="x1-101202r28"></a><span
class="cmr-6">28</span><span
-<h3 class="sectionHead"><span class="titlemark">8 </span> <a
+<h3 class="sectionHead"><span class="titlemark">8
. </span> <a
id="x1-1020008"></a>Residue setup and decode</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.1
. </span> <a
id="x1-1030008.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >A residue vector represents the fine detail of the audio spectrum of one channel in an audio frame
after the encoder subtracts the floor curve and performs any channel coupling. A residue vector
different encoding variants (numbered 0, 1 and 2) of the same basic vector encoding
abstraction.
<!--l. 23--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.2
. </span> <a
id="x1-1040008.2"></a>Residue format</h4>
<!--l. 25--><p class="noindent" >Residue format partitions each vector in the vector bundle into chunks, classifies each
chunk, encodes the chunk classifications and finally encodes the chunks themselves
follows:
<ul class="itemize1">
<li class="itemize">Each vector is partitioned into multiple equal sized chunks according to configuration
- specified. If we have a vector size of <span
-class="cmti-12">n</span>, a partition size <span
-class="cmti-12">residue˙partition˙size</span>, and
- a total of <span
-class="cmti-12">ch </span>residue vectors, the total number of partitioned chunks coded is
+ specified. If we have a vector size of <span
+class="cmti-12">n</span>, a partition size <span
+class="cmti-12">residue</span><span
+class="cmti-12">_partition</span><span
+class="cmti-12">_size</span>,
+ and a total of <span
+class="cmti-12">ch </span>residue vectors, the total number of partitioned chunks coded
- <span
+ is <span
class="cmti-12">n</span>/<span
-class="cmti-12">residue˙partition˙size</span>*<span
-class="cmti-12">ch</span>. It is important to note that the integer division truncates.
- In the below example, we assume an example <span
-class="cmti-12">residue˙partition˙size </span>of 8.
+class="cmti-12">residue</span><span
+class="cmti-12">_partition</span><span
+class="cmti-12">_size</span>*<span
+class="cmti-12">ch</span>. It is important to note that the integer division
+ truncates. In the below example, we assume an example <span
+class="cmti-12">residue</span><span
+class="cmti-12">_partition</span><span
+class="cmti-12">_size </span>of 8.
</li>
<li class="itemize">Each partition in each vector has a classification number that specifies which of
multiple configured VQ codebook setups are used to decode that partition. The
class="content">illustration of residue vector format</span></div><!--tex4ht:label?: x1-10400111 -->
</div>
<!--l. 77--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.3 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.3
. </span> <a
id="x1-1050008.3"></a>residue 0</h4>
<!--l. 79--><p class="noindent" >Residue 0 and 1 differ only in the way the values within a residue partition are interleaved during
partition encoding (visually treated as a black box–or cyan box or brown box–in the above
<!--l. 106--><p class="noindent" >It is worth mentioning at this point that no configurable value in the residue coding setup is
restricted to a power of two.
<!--l. 111--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.4 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.4
. </span> <a
id="x1-1060008.4"></a>residue 1</h4>
<!--l. 113--><p class="noindent" >Residue 1 does not interleave VQ encoding. It represents partition vector scalars in order. As
with residue 0, however, partition length must be an integer multiple of the codebook dimension,
</div>
<!--l. 137--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.5 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.5
. </span> <a
id="x1-1070008.5"></a>residue 2</h4>
<!--l. 139--><p class="noindent" >Residue type two can be thought of as a variant of residue type 1. Rather than encoding multiple
passed-in vectors as in residue type 1, the <span
class="content">illustration of residue type 2</span></div><!--tex4ht:label?: x1-10700112 -->
</div>
<!--l. 153--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">8.6 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">8.6
. </span> <a
id="x1-1080008.6"></a>Residue decode</h4>
<!--l. 155--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">8.6.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">8.6.1
. </span> <a
id="x1-1090008.6.1"></a>header decode</h5>
<!--l. 157--><p class="noindent" >Header decode for all three residue types is identical.
<div class="fancyvrb" id="fancyvrb35">
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 1)</span><span
-class="cmtt-8"> [residue_begin]</span><span
+class="cmtt-8"> [residue\_begin]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 24</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
-class="cmtt-8"> [residue_end]</span><span
+class="cmtt-8"> [residue\_end]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 24</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
-class="cmtt-8"> [residue_partition_size]</span><span
+class="cmtt-8"> [residue\_partition\_size]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 24</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
-class="cmtt-8"> [residue_classifications]</span><span
+class="cmtt-8"> [residue\_classifications]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 6</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 5)</span><span
-class="cmtt-8"> [residue_classbook]</span><span
+class="cmtt-8"> [residue\_classbook]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 8</span><span
class="cmtt-8"> range</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> ...</span><span
-class="cmtt-8"> [residue_classifications]-1</span><span
+class="cmtt-8"> [residue\_classifications]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
id="x1-109014r2"></a><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
-class="cmtt-8"> [high_bits]</span><span
+class="cmtt-8"> [high\_bits]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> 0</span>
<br class="fancyvrb" /><a
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
-class="cmtt-8"> [low_bits]</span><span
+class="cmtt-8"> [low\_bits]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> 3</span><span
class="cmtt-8"> set</span><span
class="cmtt-8"> )</span><span
class="cmtt-8"> then</span><span
-class="cmtt-8"> [high_bits]</span><span
+class="cmtt-8"> [high\_bits]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> five</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 6)</span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [residue_cascade]</span><span
+class="cmtt-8"> [residue\_cascade]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [i]</span><span
class="cmtt-8"> =</span><span
-class="cmtt-8"> [high_bits]</span><span
+class="cmtt-8"> [high\_bits]</span><span
class="cmtt-8"> *</span><span
class="cmtt-8"> 8</span><span
class="cmtt-8"> +</span><span
-class="cmtt-8"> [low_bits]</span>
+class="cmtt-8"> [low\_bits]</span>
<br class="fancyvrb" /><a
id="x1-109026r8"></a><span
class="cmr-6">8</span><span
class="cmtt-8"> range</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> ...</span><span
-class="cmtt-8"> [residue_classifications]-1</span><span
+class="cmtt-8"> [residue\_classifications]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
id="x1-109032r2"></a><span
class="cmtt-8"> if</span><span
class="cmtt-8"> (</span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [residue_cascade]</span><span
+class="cmtt-8"> [residue\_cascade]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [i]</span><span
class="cmtt-8"> bit</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
class="cmtt-8"> array</span><span
-class="cmtt-8"> [residue_books]</span><span
+class="cmtt-8"> [residue\_books]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [i][j]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 5)</span><span
class="cmtt-8"> array</span><span
-class="cmtt-8"> [residue_books]</span><span
+class="cmtt-8"> [residue\_books]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [i][j]</span><span
class="cmtt-8"> =</span><span
<!--l. 231--><p class="noindent" >An end-of-packet condition at any point in header decode renders the stream undecodable.
In addition, any codebook number greater than the maximum numbered codebook
set up in this stream also renders the stream undecodable. All codebooks in array
-[residue˙books] are required to have a value mapping. The presence of codebook in array
-[residue˙books] without a value mapping (maptype equals zero) renders the stream
+[residue_books] are required to have a value mapping. The presence of codebook in array
+[residue_books] without a value mapping (maptype equals zero) renders the stream
undecodable.
<!--l. 241--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">8.6.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">8.6.2
. </span> <a
id="x1-1100008.6.2"></a>packet decode</h5>
<!--l. 243--><p class="noindent" >Format 0 and 1 packet decode is identical except for specific partition interleave. Format 2 packet
decode can be built out of the format 1 decode process. Thus we describe first the decode
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 1)</span><span
-class="cmtt-8"> [actual_size]</span><span
+class="cmtt-8"> [actual\_size]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> current</span><span
class="cmtt-8"> blocksize/2;</span>
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
-class="cmtt-8"> [actual_size]</span><span
+class="cmtt-8"> [actual\_size]</span><span
class="cmtt-8"> =</span><span
-class="cmtt-8"> [actual_size]</span><span
+class="cmtt-8"> [actual\_size]</span><span
class="cmtt-8"> *</span><span
class="cmtt-8"> [ch];</span>
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
-class="cmtt-8"> [limit_residue_begin]</span><span
+class="cmtt-8"> [limit\_residue\_begin]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> maximum</span><span
class="cmtt-8"> of</span><span
-class="cmtt-8"> ([residue_begin],[actual_size]);</span>
+class="cmtt-8"> ([residue\_begin],[actual\_size]);</span>
<br class="fancyvrb" /><a
id="x1-110010r5"></a><span
class="cmr-6">5</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 5)</span><span
-class="cmtt-8"> [limit_residue_end]</span><span
+class="cmtt-8"> [limit\_residue\_end]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> maximum</span><span
class="cmtt-8"> of</span><span
-class="cmtt-8"> ([residue_end],[actual_size]);</span>
+class="cmtt-8"> ([residue\_end],[actual\_size]);</span>
</div>
<!--l. 277--><p class="noindent" >The following convenience values are conceptually useful to clarifying the decode process:
<!--l. 280--><p class="noindent" >
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 1)</span><span
-class="cmtt-8"> [classwords_per_codeword]</span><span
+class="cmtt-8"> [classwords\_per\_codeword]</span><span
class="cmtt-8"> =</span><span
-class="cmtt-8"> [codebook_dimensions]</span><span
+class="cmtt-8"> [codebook\_dimensions]</span><span
class="cmtt-8"> value</span><span
class="cmtt-8"> of</span><span
class="cmtt-8"> codebook</span><span
-class="cmtt-8"> [residue_classbook]</span>
+class="cmtt-8"> [residue\_classbook]</span>
<br class="fancyvrb" /><a
id="x1-110014r2"></a><span
class="cmr-6">2</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
-class="cmtt-8"> [n_to_read]</span><span
+class="cmtt-8"> [n\_to\_read]</span><span
class="cmtt-8"> =</span><span
-class="cmtt-8"> [limit_residue_end]</span><span
+class="cmtt-8"> [limit\_residue\_end]</span><span
class="cmtt-8"> -</span><span
-class="cmtt-8"> [limit_residue_begin]</span>
+class="cmtt-8"> [limit\_residue\_begin]</span>
<br class="fancyvrb" /><a
id="x1-110016r3"></a><span
class="cmr-6">3</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
-class="cmtt-8"> [partitions_to_read]</span><span
+class="cmtt-8"> [partitions\_to\_read]</span><span
class="cmtt-8"> =</span><span
-class="cmtt-8"> [n_to_read]</span><span
+class="cmtt-8"> [n\_to\_read]</span><span
class="cmtt-8"> /</span><span
-class="cmtt-8"> [residue_partition_size]</span>
+class="cmtt-8"> [residue\_partition\_size]</span>
</div>
<!--l. 286--><p class="noindent" >Packet decode proceeds as follows, matching the description offered earlier in the document.
<div class="fancyvrb" id="fancyvrb40">
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
class="cmtt-8"> if</span><span
-class="cmtt-8"> ([n_to_read]</span><span
+class="cmtt-8"> ([n\_to\_read]</span><span
class="cmtt-8"> is</span><span
class="cmtt-8"> zero),</span><span
class="cmtt-8"> stop;</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
-class="cmtt-8"> [partition_count]</span><span
+class="cmtt-8"> [partition\_count]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> 0</span>
<br class="fancyvrb" /><a
class="cmtt-8"> </span><span
class="cmtt-8"> 5)</span><span
class="cmtt-8"> while</span><span
-class="cmtt-8"> [partition_count]</span><span
+class="cmtt-8"> [partition\_count]</span><span
class="cmtt-8"> is</span><span
class="cmtt-8"> less</span><span
class="cmtt-8"> than</span><span
-class="cmtt-8"> [partitions_to_read]</span>
+class="cmtt-8"> [partitions\_to\_read]</span>
<br class="fancyvrb" /><a
id="x1-110032r8"></a><span
class="cmr-6">8</span><span
class="cmtt-8"> packet</span><span
class="cmtt-8"> using</span><span
class="cmtt-8"> codebook</span><span
-class="cmtt-8"> [residue_classbook]</span><span
+class="cmtt-8"> [residue\_classbook]</span><span
class="cmtt-8"> in</span><span
class="cmtt-8"> scalar</span><span
class="cmtt-8"> context</span>
class="cmtt-8"> over</span><span
class="cmtt-8"> the</span><span
class="cmtt-8"> range</span><span
-class="cmtt-8"> [classwords_per_codeword]-1</span><span
+class="cmtt-8"> [classwords\_per\_codeword]-1</span><span
class="cmtt-8"> ...</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> {</span>
class="cmtt-8"> array</span><span
class="cmtt-8"> [classifications]</span><span
class="cmtt-8"> element</span><span
-class="cmtt-8"> [j],([i]+[partition_count])</span><span
+class="cmtt-8"> [j],([i]+[partition\_count])</span><span
class="cmtt-8"> =</span>
<br class="fancyvrb" /><a
id="x1-110054r19"></a><span
class="cmtt-8"> [temp]</span><span
class="cmtt-8"> integer</span><span
class="cmtt-8"> modulo</span><span
-class="cmtt-8"> [residue_classifications]</span>
+class="cmtt-8"> [residue\_classifications]</span>
<br class="fancyvrb" /><a
id="x1-110056r20"></a><span
class="cmr-6">20</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> [temp]</span><span
class="cmtt-8"> /</span><span
-class="cmtt-8"> [residue_classifications]</span><span
+class="cmtt-8"> [residue\_classifications]</span><span
class="cmtt-8"> using</span><span
class="cmtt-8"> integer</span><span
class="cmtt-8"> division</span>
class="cmtt-8"> range</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> ..</span><span
-class="cmtt-8"> ([classwords_per_codeword]</span><span
+class="cmtt-8"> ([classwords\_per\_codeword]</span><span
class="cmtt-8"> -</span><span
class="cmtt-8"> 1)</span><span
class="cmtt-8"> while</span><span
-class="cmtt-8"> [partition_count]</span>
+class="cmtt-8"> [partition\_count]</span>
<br class="fancyvrb" /><a
id="x1-110078r31"></a><span
class="cmr-6">31</span><span
class="cmtt-8"> also</span><span
class="cmtt-8"> less</span><span
class="cmtt-8"> than</span><span
-class="cmtt-8"> [partitions_to_read]</span><span
+class="cmtt-8"> [partitions\_to\_read]</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
id="x1-110080r32"></a><span
class="cmtt-8"> array</span><span
class="cmtt-8"> [classifications]</span><span
class="cmtt-8"> element</span><span
-class="cmtt-8"> [j],[partition_count]</span>
+class="cmtt-8"> [j],[partition\_count]</span>
<br class="fancyvrb" /><a
id="x1-110092r38"></a><span
class="cmr-6">38</span><span
class="cmtt-8"> [vqbook]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> array</span><span
-class="cmtt-8"> [residue_books]</span><span
+class="cmtt-8"> [residue\_books]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [vqclass],[pass]</span>
<br class="fancyvrb" /><a
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> offset</span><span
-class="cmtt-8"> [limit_residue_begin]+[partition_count]*[residue_partition_size]</span><span
+class="cmtt-8"> [limit\_residue\_begin]+[partition\_count]*[residue\_partition\_size]</span><span
class="cmtt-8"> using</span>
<br class="fancyvrb" /><a
id="x1-110102r43"></a><span
class="cmtt-8"> </span><span
class="cmtt-8"> 20)</span><span
class="cmtt-8"> increment</span><span
-class="cmtt-8"> [partition_count]</span><span
+class="cmtt-8"> [partition\_count]</span><span
class="cmtt-8"> by</span><span
class="cmtt-8"> one</span>
<br class="fancyvrb" /><a
<!--l. 344--><p class="noindent" >An end-of-packet condition during packet decode is to be considered a nominal occurrence.
Decode returns the result of vector decode up to that point.
<!--l. 350--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">8.6.3 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">8.6.3
. </span> <a
id="x1-1110008.6.3"></a>format 0 specifics</h5>
<!--l. 352--><p class="noindent" >Format zero decodes partitions exactly as described earlier in the ’Residue Format: residue 0’
section. The following pseudocode presents the same algorithm. Assume:
class="cmtt-8"> =</span><span
class="cmtt-8"> [n]</span><span
class="cmtt-8"> /</span><span
-class="cmtt-8"> [codebook_dimensions]</span>
+class="cmtt-8"> [codebook\_dimensions]</span>
<br class="fancyvrb" /><a
id="x1-111004r2"></a><span
class="cmr-6">2</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [entry_temp]</span><span
+class="cmtt-8"> [entry\_temp]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> vector</span><span
class="cmtt-8"> range</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> ...</span><span
-class="cmtt-8"> [codebook_dimensions]-1</span><span
+class="cmtt-8"> [codebook\_dimensions]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
id="x1-111012r6"></a><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [entry_temp]</span><span
+class="cmtt-8"> [entry\_temp]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [j]</span>
<br class="fancyvrb" /><a
</div>
<!--l. 384--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">8.6.4 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">8.6.4
. </span> <a
id="x1-1120008.6.4"></a>format 1 specifics</h5>
<!--l. 386--><p class="noindent" >Format 1 decodes partitions exactly as described earlier in the ’Residue Format: residue 1’
section. The following pseudocode presents the same algorithm. Assume:
class="cmtt-8"> </span><span
class="cmtt-8"> 2)</span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [entry_temp]</span><span
+class="cmtt-8"> [entry\_temp]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> read</span><span
class="cmtt-8"> vector</span><span
class="cmtt-8"> range</span><span
class="cmtt-8"> 0</span><span
class="cmtt-8"> ...</span><span
-class="cmtt-8"> [codebook_dimensions]-1</span><span
+class="cmtt-8"> [codebook\_dimensions]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
id="x1-112008r4"></a><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> vector</span><span
-class="cmtt-8"> [entry_temp]</span><span
+class="cmtt-8"> [entry\_temp]</span><span
class="cmtt-8"> element</span><span
class="cmtt-8"> [j]</span>
<br class="fancyvrb" /><a
class="cmtt-8"> done</span>
</div>
<!--l. 416--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">8.6.5 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">8.6.5
. </span> <a
id="x1-1130008.6.5"></a>format 2 specifics</h5>
<!--l. 418--><p class="noindent" >Format 2 is reducible to format 1. It may be implemented as an additional step prior to and an
additional post-decode step after a normal format 1 decode.
representing all output channels, rather than a vector for each channel. After decode,
deinterleave the vector into independent vectors, one for each output channel. That
is:
-<!--l. 42
8--><p class="noindent" >
- <ol class="enumerate1" >
- <li
- class="enumerate" id="x1-113002x1">If all vectors 0 through <span
+<!--l. 42
9--><p class="noindent" >
+ <dl class="enumerate-enumitem"><dt class="enumerate-enumitem">
+ 1. </dt><dd
+class="enumerate-enumitem">If all vectors 0 through <span
class="cmti-12">ch</span>-1 are marked ’do not decode’, allocate and clear a single
vector <span
class="cmtt-12">[v]</span>of length <span
class="cmti-12">ch*n </span>and skip step 2 below; proceed directly to the post-decode
step.
- </li>
- <li
- class="enumerate" id="x1-113004x2">Rather than performing format 1 decode to produce <span
+ </dd><dt class="enumerate-enumitem">
+ 2. </dt><dd
+class="enumerate-enumitem">Rather than performing format 1 decode to produce <span
class="cmti-12">ch </span>vectors of length <span
class="cmti-12">n </span>each, call
format 1 decode to produce a single vector <span
class="cmtt-12">[v] </span>of length <span
class="cmti-12">ch*n</span>.
- </li>
- <li
- class="enumerate" id="x1-113006x3">Post decode: Deinterleave the single vector <span
+ </dd><dt class="enumerate-enumitem">
+ 3. </dt><dd
+class="enumerate-enumitem">Post decode: Deinterleave the single vector <span
class="cmtt-12">[v] </span>returned by format 1 decode as
described above into <span
class="cmti-12">ch </span>independent vectors, one for each outputchannel, according
to:
<div class="fancyvrb" id="fancyvrb43">
<a
- id="x1-113008r1"></a><span
+ id="x1-113005r1"></a><span
class="cmr-6">1</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> [n]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
- id="x1-113010r2"></a><span
+ id="x1-113007r2"></a><span
class="cmr-6">2</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-113012r3"></a><span
+ id="x1-113009r3"></a><span
class="cmr-6">3</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> [ch]-1</span><span
class="cmtt-8"> {</span>
<br class="fancyvrb" /><a
- id="x1-113014r4"></a><span
+ id="x1-113011r4"></a><span
class="cmr-6">4</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-113016r5"></a><span
+ id="x1-113013r5"></a><span
class="cmr-6">5</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> +</span><span
class="cmtt-8"> [j])</span>
<br class="fancyvrb" /><a
- id="x1-113018r6"></a><span
+ id="x1-113015r6"></a><span
class="cmr-6">6</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-113020r7"></a><span
+ id="x1-113017r7"></a><span
class="cmr-6">7</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> }</span>
<br class="fancyvrb" /><a
- id="x1-113022r8"></a><span
+ id="x1-113019r8"></a><span
class="cmr-6">8</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> }</span>
<br class="fancyvrb" /><a
- id="x1-113024r9"></a><span
+ id="x1-113021r9"></a><span
class="cmr-6">9</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span>
<br class="fancyvrb" /><a
- id="x1-113026r10"></a><span
+ id="x1-113023r10"></a><span
class="cmr-6">10</span><span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 4)</span><span
class="cmtt-8"> done</span>
</div>
- </li></ol>
+ </dd></dl>
-<h3 class="sectionHead"><span class="titlemark">9 </span> <a
+<h3 class="sectionHead"><span class="titlemark">9
. </span> <a
id="x1-1140009"></a>Helper equations</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">9.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">9.1
. </span> <a
id="x1-1150009.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >The equations below are used in multiple places by the Vorbis codec specification. Rather than
cluttering up the main specification documents, they are defined here and referenced where
appropriate.
<!--l. 13--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">9.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">9.2
. </span> <a
id="x1-1160009.2"></a>Functions</h4>
<!--l. 15--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.1
. </span> <a
id="x1-1170009.2.1"></a>ilog</h5>
<!--l. 17--><p class="noindent" >The ”ilog(x)” function returns the position number (1 through n) of the highest set bit in the
two’s complement integer value <span
class="cmtt-8"> </span><span
class="cmtt-8"> </span><span
class="cmtt-8"> 1)</span><span
-class="cmtt-8"> [return_value]</span><span
+class="cmtt-8"> [return\_value]</span><span
class="cmtt-8"> =</span><span
class="cmtt-8"> 0;</span>
<br class="fancyvrb" /><a
class="cmtt-8"> </span><span
class="cmtt-8"> 3)</span><span
class="cmtt-8"> increment</span><span
-class="cmtt-8"> [return_value];</span>
+class="cmtt-8"> [return\_value];</span>
<br class="fancyvrb" /><a
id="x1-117010r5"></a><span
class="cmr-6">5</span><span
</li>
<li class="itemize">ilog(negative number) = 0;</li></ul>
<!--l. 48--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.2 </span> <a
- id="x1-1180009.2.2"></a>float32˙unpack</h5>
-<!--l. 50--><p class="noindent" >”float32˙unpack(x)” is intended to translate the packed binary representation of a Vorbis
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.2
. </span> <a
+ id="x1-1180009.2.2"></a>float32_unpack</h5>
+<!--l. 50--><p class="noindent" >”float32_unpack(x)” is intended to translate the packed binary representation of a Vorbis
codebook float value into the representation used by the decoder for floating point numbers. For
purposes of this example, we will unpack a Vorbis float32 into a host-native floating point
number.
<!--l. 66--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.3 </span> <a
- id="x1-1190009.2.3"></a>lookup1˙values</h5>
-<!--l. 68--><p class="noindent" >”lookup1˙values(codebook˙entries,codebook˙dimensions)” is used to compute the correct length of
-the value index for a codebook VQ lookup table of lookup type 1. The values on this list are
-permuted to construct the VQ vector lookup table of size <span
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.3. </span> <a
+ id="x1-1190009.2.3"></a>lookup1_values</h5>
+<!--l. 68--><p class="noindent" >”lookup1_values(codebook_entries,codebook_dimensions)” is used to compute the
+correct length of the value index for a codebook VQ lookup table of lookup type 1.
+The values on this list are permuted to construct the VQ vector lookup table of size
+<span
class="cmtt-12">[codebook_entries]</span>.
<!--l. 74--><p class="noindent" >The return value for this function is defined to be ’the greatest integer value for which
<span
<span
class="cmtt-12">[codebook_entries]</span>’.
<!--l. 81--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.4 </span> <a
- id="x1-1200009.2.4"></a>low˙neighbor</h5>
-<!--l. 83--><p class="noindent" >”low˙neighbor(v,x)” finds the position <span
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.4
. </span> <a
+ id="x1-1200009.2.4"></a>low_neighbor</h5>
+<!--l. 83--><p class="noindent" >”low_neighbor(v,x)” finds the position <span
class="cmtt-12">n </span>in vector <span
class="cmtt-12">[v] </span>of the greatest value scalar element for
which <span
<span
class="cmtt-12">[x]</span>.
<!--l. 88--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.5 </span> <a
- id="x1-1210009.2.5"></a>high˙neighbor</h5>
-<!--l. 90--><p class="noindent" >”high˙neighbor(v,x)” finds the position <span
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.5
. </span> <a
+ id="x1-1210009.2.5"></a>high_neighbor</h5>
+<!--l. 90--><p class="noindent" >”high_neighbor(v,x)” finds the position <span
class="cmtt-12">n </span>in vector [v] of the lowest value scalar element for
which <span
class="cmtt-12">n </span>is less than <span
<span
class="cmtt-12">[x]</span>.
<!--l. 97--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.6 </span> <a
- id="x1-1220009.2.6"></a>render˙point</h5>
-<!--l. 99--><p class="noindent" >”render˙point(x0,y0,x1,y1,X)” is used to find the Y value at point X along the line specified by
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.6
. </span> <a
+ id="x1-1220009.2.6"></a>render_point</h5>
+<!--l. 99--><p class="noindent" >”render_point(x0,y0,x1,y1,X)” is used to find the Y value at point X along the line specified by
x0, x1, y0 and y1. This function uses an integer algorithm to solve for the point directly without
calculating intervening values along the line.
-<!--l. 104--><p class="noindent" >
+<!--l. 104--><p class="noindent" >
<div class="fancyvrb" id="fancyvrb46">
<a
id="x1-122002r1"></a><span
class="cmtt-8"> done</span>
</div>
<!--l. 125--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">9.2.7 </span> <a
- id="x1-1230009.2.7"></a>render˙line</h5>
-<!--l. 127--><p class="noindent" >Floor decode type one uses the integer line drawing algorithm of ”render˙line(x0, y0, x1, y1, v)”
+<h5 class="subsubsectionHead"><span class="titlemark">9.2.7
. </span> <a
+ id="x1-1230009.2.7"></a>render_line</h5>
+<!--l. 127--><p class="noindent" >Floor decode type one uses the integer line drawing algorithm of ”render_line(x0, y0, x1, y1, v)”
to construct an integer floor curve for contiguous piecewise line segments. Note that it has not
been relevant elsewhere, but here we must define integer division as rounding division of both
positive and negative numbers toward zero.
class="cmtt-8"> ...</span><span
class="cmtt-8"> [x1]-1</span><span
class="cmtt-8"> {</span>
+
+
+
<br class="fancyvrb" /><a
id="x1-123046r23"></a><span
class="cmr-6">23</span><span
class="cmtt-8"> [err]</span><span
class="cmtt-8"> +</span><span
class="cmtt-8"> [ady];</span>
-
-
-
<br class="fancyvrb" /><a
id="x1-123050r25"></a><span
class="cmr-6">25</span><span
-<h3 class="sectionHead"><span class="titlemark">10 </span> <a
+<h3 class="sectionHead"><span class="titlemark">10
. </span> <a
id="x1-12400010"></a>Tables</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">10.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">10.1
. </span> <a
id="x1-12500010.1"></a>floor1_inverse_dB_table</h4>
<!--l. 8--><p class="noindent" >The vector <span
class="cmtt-12">[floor1_inverse_dB_table] </span>is a 256 element static lookup table consiting of the
-<h3 class="sectionHead"><span class="titlemark">A </span> <a
+<h3 class="sectionHead"><span class="titlemark">A
. </span> <a
id="x1-126000A"></a>Embedding Vorbis into an Ogg stream</h3>
<!--l. 6--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">A.1 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">A.1
. </span> <a
id="x1-127000A.1"></a>Overview</h4>
<!--l. 8--><p class="noindent" >This document describes using Ogg logical and physical transport streams to encapsulate Vorbis
compressed audio packet data into file form.
knowledge of the concepts covered in these named backround documents. Please read them
first.
<!--l. 22--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">A.1.1 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">A.1.1
. </span> <a
id="x1-128000A.1.1"></a>Restrictions</h5>
<!--l. 24--><p class="noindent" >The Ogg/Vorbis I specification currently dictates that Ogg/Vorbis streams use Ogg transport
streams in degenerate, unmultiplexed form only. That is:
stream (naturally, application authors are encouraged to support full multiplexed Ogg
handling).
<!--l. 55--><p class="noindent" >
-<h5 class="subsubsectionHead"><span class="titlemark">A.1.2 </span> <a
+<h5 class="subsubsectionHead"><span class="titlemark">A.1.2
. </span> <a
id="x1-129000A.1.2"></a>MIME type</h5>
<!--l. 57--><p class="noindent" >The MIME type of Ogg files depend on the context. Specifically, complex multimedia and
applications should use <span
class="cmtt-12">audio/vorbis </span>+ <span
class="cmtt-12">audio/vorbis-config</span>.
<!--l. 65--><p class="noindent" >
-<h4 class="subsectionHead"><span class="titlemark">A.2 </span> <a
+<h4 class="subsectionHead"><span class="titlemark">A.2
. </span> <a
id="x1-130000A.2"></a>Encapsulation</h4>
<!--l. 67--><p class="noindent" >Ogg encapsulation of a Vorbis packet stream is straightforward.
<ul class="itemize1">
-<h3 class="sectionHead"><span class="titlemark">B </span> <a
+<h3 class="sectionHead"><span class="titlemark">B
. </span> <a
id="x1-132000B"></a>Vorbis encapsulation in RTP</h3>
<!--l. 8--><p class="noindent" >Please consult RFC 5215 <span
class="cmti-12">“RTP Payload Format for Vorbis Encoded Audio” </span>for description of
name="Vorbis_I_spec13x.png" src="xifish.pdf"
-->
<!--l. 10--><p class="noindent" >Ogg is a <a
-href="http://www.xiph.org/" >Xiph.org Foundation</a> effort to protect essential tenets of Internet multimedia from
+href="http://www.xiph.org/" >Xiph.Org Foundation</a> effort to protect essential tenets of Internet multimedia from
corporate hostage-taking; Open Source is the net’s greatest tool to keep everyone honest. See
<a
-href="http://www.xiph.org/about.html" >About the Xiph.org Foundation</a> for details.
+href="http://www.xiph.org/about.html" >About the Xiph.Org Foundation</a> for details.
<!--l. 17--><p class="noindent" >Ogg Vorbis is the first Ogg audio CODEC. Anyone may freely use and distribute the Ogg and
-Vorbis specification, whether in a private, public or corporate capacity. However, the Xiph.org
+Vorbis specification, whether in a private, public or corporate capacity. However, the Xiph.Org
Foundation and the Ogg project (xiph.org) reserve the right to set the Ogg Vorbis specification
and certify specification compliance.
-<!--l. 23--><p class="noindent" >Xiph.org’s Vorbis software CODEC implementation is distributed under a BSD-like license. This
+<!--l. 23--><p class="noindent" >Xiph.Org’s Vorbis software CODEC implementation is distributed under a BSD-like license. This
does not restrict third parties from distributing independent implementations of Vorbis software
under other licenses.
-<!--l. 28--><p class="noindent" >Ogg, Vorbis, Xiph.
org Foundation and their logos are trademarks (tm) of the <a
-href="http://www.xiph.org/" >Xiph.org
-Foundation</a>. These pages are copyright (C) 1994-2007 Xiph.org Foundation. All rights
+<!--l. 28--><p class="noindent" >Ogg, Vorbis, Xiph.
Org Foundation and their logos are trademarks (tm) of the <a
+href="http://www.xiph.org/" >Xiph.Org
+Foundation</a>. These pages are copyright (C) 1994-2007 Xiph.Org Foundation. All rights
reserved.
<!--l. 33--><p class="noindent" >This document is set using <span class="LATEX">L<span class="A">A</span><span class="TEX">T<span
class="E">E</span>X</span></span>.
<h3 class="likesectionHead"><a
id="x1-134000B"></a>References</h3>
-<!--l. 12
3--><p class="noindent" >
+<!--l. 12
5--><p class="noindent" >
<div class="thebibliography">
<p class="bibitem" ><span class="biblabel">
[1]<span class="bibsp">   </span></span><a
projects / platform / upstream / libvorbis.git / blobdiff