+2004-01-26 Ronald Bultje <rbultje@ronald.bitfreak.net>
+
+ * docs/pwg/advanced_types.xml:
+ * docs/pwg/intro_basics.xml:
+ * docs/pwg/intro_preface.xml:
+ * docs/pwg/pwg.xml:
+ * docs/pwg/titlepage.xml:
+ First try to resurrect the PWG. I'm halfway integrating the mimetypes
+ in here (docs/random/mimetypes), and will from there on work on both
+ updating outdated parts and adding missing parts.
+ That doesn't mean I'll fix it completely, but I'll try at least. ;).
+
2004-01-26 Thomas Vander Stichele <thomas at apestaart dot org>
* gst/gsterror.h: reinstate GST_LIBRARY_ERROR_ENCODE until
<para>
</para>
</sect1>
+
+ <!-- ############ sect1 ############# -->
+
+ <sect1 id="sect1-types-definitions" xreflabel="List of Defined Types">
+ <title>List of Defined Types</title>
+ <para>
+ Below is a list of all the defined types in &GStreamer;. They are split
+ up in separate tables for audio, video, container, text and other
+ types, for the sake of readability. Below each table might follow a
+ list of notes that apply to that table. In the definition of each type,
+ we try to follow the types and rules as defined by <ulink type="http"
+ url="http://www.isi.edu/in-notes/iana/assignments/media-types/media-types">
+ IANA</ulink> for as far as possible.
+ </para>
+ <para>
+ Note that many of the properties are not <emphasis>required</emphasis>,
+ but rather <emphasis>optional</emphasis> properties. This means that
+ most of these properties can be extracted from the container header,
+ but that - in case the container header does not provide these - they
+ can also be extracted by parsing the stream header or the stream
+ content. The policy is that your element should provide the data that
+ it knows about by only parsing its own content, not another element's
+ content. Example: the AVI header provides samplerate of the contained
+ audio stream in the header. MPEG system streams don't. This means that
+ an AVI stream demuxer would provide samplerate as a property for MPEG
+ audio streams, whereas an MPEG demuxer would not.
+ </para>
+
+ <table frame="all" id="table-audio-types" xreflabel="Table of Audio Types">
+ <title>Table of Audio Types</title>
+ <tgroup cols="6" align="left" colsep="1" rowsep="1">
+ <colspec colnum="1" colname="cola1" colwidth="1*"/>
+ <colspec colnum="6" colname="cola6" colwidth="6*"/>
+ <spanspec spanname="fullwidth" namest="cola1" nameend="cola6"/>
+
+ <thead>
+ <row>
+ <entry>Mime Type</entry>
+ <entry>Description</entry>
+ <entry>Property</entry>
+ <entry>Property Type</entry>
+ <entry>Property Values</entry>
+ <entry>Property Description</entry>
+ </row>
+ </thead>
+
+ <tbody valign="top">
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All audio types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry morerows="1">audio/*</entry>
+ <entry morerows="1">
+ <emphasis>All audio types</emphasis>
+ </entry>
+ <entry>rate</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The sample rate of the data, in samples (per channel) per second.
+ </entry>
+ </row>
+ <row>
+ <entry>channels</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The number of channels of audio data.
+ </entry>
+ </row>
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All raw audio types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry morerows="3">audio/x-raw-int</entry>
+ <entry morerows="3">
+ Unstructured and uncompressed raw fixed-integer audio data.
+ </entry>
+ <entry>endianness</entry>
+ <entry>integer</entry>
+ <entry>G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321)</entry>
+ <entry>
+ The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321)
+ means <quote>little-endian</quote> (byte-order is <quote>least
+ significant byte first</quote>). The value G_BIG_ENDIAN (1234)
+ means <quote>big-endian</quote> (byte order is <quote>most
+ significant byte first</quote>).
+ </entry>
+ </row>
+ <row>
+ <entry>signed</entry>
+ <entry>boolean</entry>
+ <entry>TRUE or FALSE</entry>
+ <entry>
+ Whether the values of the integer samples are signed or not.
+ Signed samples use one bit to indicate sign (negative or
+ positive) of the value. Unsigned samples are always positive.
+ </entry>
+ </row>
+ <row>
+ <entry>width</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ Number of bits allocated per sample.
+ </entry>
+ </row>
+ <row>
+ <entry>depth</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The number of bits used per sample. This must be less than or
+ equal to the width: If the depth is less than the width, the
+ low bits are assumed to be the ones used. For example, a width
+ of 32 and a depth of 24 means that each sample is stored in a
+ 32 bit word, but only the low 24 bits are actually used.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry morerows="2">audio/x-raw-float</entry>
+ <entry morerows="2">
+ Unstructured and uncompressed raw floating-point audio data.
+ </entry>
+ <entry>endianness</entry>
+ <entry>integer</entry>
+ <entry>G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321)</entry>
+ <entry>
+ The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321)
+ means <quote>little-endian</quote> (byte-order is <quote>least
+ significant byte first</quote>). The value G_BIG_ENDIAN (1234)
+ means <quote>big-endian</quote> (byte order is <quote>most
+ significant byte first</quote>).
+ </entry>
+ </row>
+ <row>
+ <entry>width</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The amount of bits used and allocated per sample.
+ </entry>
+ </row>
+ <row>
+ <entry>buffer-frames</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The number of frames per buffer. The reason for this property
+ is that the element does not need to reuse buffers or use data
+ spanned over multiple buffers, so this property - when used
+ rightly - will decrease latency. Note that some people think that
+ this property is very ugly, whereas others think it is vital for
+ the use of &GStreamer; in professional audio applications.
+ </entry>
+ </row>
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All encoded audio types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-ac3</entry>
+ <entry>AC-3 or A52 audio streams.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-adpcm</entry>
+ <entry>ADPCM Audio streams.</entry>
+ <entry>layout</entry>
+ <entry>string</entry>
+ <entry>
+ <quote>quicktime</quote>, <quote>wav</quote>,
+ <quote>microsoft</quote> or <quote>4xm</quote>.
+ </entry>
+ <entry>
+ The layout defines the packing of the samples in the stream. In
+ ADPCM, most formats store multiple samples per channel together.
+ This number of samples differs per format, hence the different
+ layouts. On the long term, we probably want this variable to die
+ and use something more descriptive, but this will do for now.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-dv</entry>
+ <entry>Audio as provided in a Digital Video stream.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-flac</entry>
+ <entry>Free Lossless Audio codec (FLAC).</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-gsm</entry>
+ <entry>Data encoded by the GSM codec.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-alaw</entry>
+ <entry>A-Law Audio.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-mulaw</entry>
+ <entry>Mu-Law Audio.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-mace</entry>
+ <entry>MACE Audio (used in Quicktime).</entry>
+ <entry>maceversion</entry>
+ <entry>integer</entry>
+ <entry>3 or 6</entry>
+ <entry>
+ The version of the MACE audio codec used to encode the stream.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry morerows="3">audio/mpeg</entry>
+ <entry morerows="3">
+ Audio data compressed using the MPEG audio encoding scehem.
+ </entry>
+ <entry>mpegversion</entry>
+ <entry>integer</entry>
+ <entry>1, 2 or 4</entry>
+ <entry>
+ The MPEG-version used for encoding the data. The value 1 refers
+ to MPEG-1, -2 and -2.5 layer 1, 2 or 3. The values 2 and 4 refer
+ to the MPEG-AAC audio encoding schemes.
+ </entry>
+ </row>
+ <row>
+ <entry>framed</entry>
+ <entry>boolean</entry>
+ <entry>0 or 1</entry>
+ <entry>
+ A true value indicates that each buffer contains exactly one
+ frame. A false value indicates that frames and buffers do not
+ necessarily match up.
+ </entry>
+ </row>
+ <row>
+ <entry>layer</entry>
+ <entry>integer</entry>
+ <entry>1, 2, or 3</entry>
+ <entry>
+ The compression scheme layer used to compress the data
+ <emphasis>(only if mpegversion=1)</emphasis>.
+ </entry>
+ </row>
+ <row>
+ <entry>bitrate</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The bitrate, in bits per second. For VBR (variable bitrate)
+ MPEG data, this is the average bitrate.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-pn-realaudio</entry>
+ <entry>Real Audio data.</entry>
+ <entry>raversion</entry>
+ <entry>integer</entry>
+ <entry>1 or 2</entry>
+ <entry>
+ The version of the Real Audio codec used to encode the stream.
+ 1 stands for a 14k4 stream, 2 stands for a 28k8 stream.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-qdm2</entry>
+ <entry>Data encoded by the QDM version 2 codec.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-speex</entry>
+ <entry>Data encoded by the Speex audio codec</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-vorbis</entry>
+ <entry>Vorbis audio data.</entry>
+ <entry></entry>
+ <entry></entry>
+ <entry></entry>
+ <entry>
+ There are currently no specific properties defined or needed for
+ this type.
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>audio/x-wma</entry>
+ <entry>Windows Media Audio</entry>
+ <entry>wmaversion</entry>
+ <entry>integer</entry>
+ <entry>1 or 2</entry>
+ <entry>
+ The version of the WMA codec used to encode the stream.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <table frame="all" id="table-video-types" xreflabel="Table of Video Types">
+ <title>Table of Video Types</title>
+ <tgroup cols="6" align="left" colsep="1" rowsep="1">
+ <colspec colnum="1" colname="colv1" colwidth="1*"/>
+ <colspec colnum="6" colname="colv6" colwidth="6*"/>
+ <spanspec spanname="fullwidth" namest="colv1" nameend="colv6"/>
+
+ <thead>
+ <row>
+ <entry>Mime Type</entry>
+ <entry>Description</entry>
+ <entry>Property</entry>
+ <entry>Property Type</entry>
+ <entry>Property Values</entry>
+ <entry>Property Description</entry>
+ </row>
+ </thead>
+
+ <tbody valign="top">
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All video types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry morerows="2">video/*</entry>
+ <entry morerows="2">
+ <emphasis>All video types</emphasis>
+ </entry>
+ <entry>width</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>The width of the video image</entry>
+ </row>
+ <row>
+ <entry>height</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>The height of the video image</entry>
+ </row>
+ <row>
+ <entry>framerate</entry>
+ <entry>double</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The (average) framerate in frames per second. Note that this
+ property does not guarantee in <emphasis>any</emphasis> way that
+ it will actually come close to this value. If you need a fixed
+ framerate, please use an element that provides that (such as
+ <quote>videodrop</quote>).
+ </entry>
+ </row>
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All raw video types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>video/x-raw-yuv</entry>
+ <entry>YUV (or Y'Cb'Cr) video format.</entry>
+ <entry>format</entry>
+ <entry>fourcc</entry>
+ <entry>
+ YUY2, YVYU, UYVY, Y41P, IYU2, Y42B, YV12, I420, Y41B, YUV9, YVU9,
+ Y800
+ </entry>
+ <entry>
+ The layout of the video. See <ulink type="http"
+ url="http://www.fourcc.org/">FourCC definition site</ulink>
+ for references and definitions. YUY2, YVYU and UYVY are 4:2:2
+ packed-pixel, Y41P is 4:1:1 packed-pixel and IYU2 is 4:4:4
+ packed-pixel. Y42B is 4:2:2 planar, YV12 and I420 are 4:2:0
+ planar, Y41B is 4:1:1 planar and YUV9 and YVU9 are 4:1:0 planar.
+ Y800 contains Y-samples only (black/white).
+ </entry>
+ </row>
+
+ <row>
+ <entry morerows="3">video/x-raw-rgb</entry>
+ <entry morerows="3">Red-Green-Blue (RBG) video.</entry>
+ <entry>bpp</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The number of bits allocated per pixel. This is usually 16, 24
+ or 32.
+ </entry>
+ </row>
+
+ <row>
+ <entry>depth</entry>
+ <entry>integer</entry>
+ <entry>greater than 0</entry>
+ <entry>
+ The number of bits used per pixel by the R/G/B components. This
+ is usually 15, 16 or 24.
+ </entry>
+ </row>
+
+ <row>
+ <entry>endianness</entry>
+ <entry>integer</entry>
+ <entry>G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321)</entry>
+ <entry>
+ The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321)
+ means <quote>little-endian</quote> (byte-order is <quote>least
+ significant byte first</quote>). The value G_BIG_ENDIAN (1234)
+ means <quote>big-endian</quote> (byte order is <quote>most
+ significant byte first</quote>). For 24/32bpp, this should always
+ be big endian because the byte order can be given in both.
+ </entry>
+ </row>
+
+ <row>
+ <entry>red_mask, green_mask and blue_mask</entry>
+ <entry>integer</entry>
+ <entry>any</entry>
+ <entry>
+ The masks that cover all the bits used by each of the samples.
+ The mask should be given in the endianness specified above. This
+ means that for 24/32bpp, the masks might be opposite to host byte
+ order (if you are working on little-endian computers).
+ </entry>
+ </row>
+
+ <!-- ############ subtitle ############# -->
+
+ <row>
+ <entry spanname="fullwidth">
+ <emphasis>All encoded video types.</emphasis>
+ </entry>
+ </row>
+
+ <!-- ############ type ############# -->
+
+ <row>
+ <entry>video/x-divx</entry>
+ <entry>DivX video.</entry>
+ <entry>divxversion</entry>
+ <entry>integer</entry>
+ <entry>3, 4 or 5</entry>
+ <entry>
+ Version of the DivX codec used to encode the stream.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect1>
</chapter>
<!-- ############ sect1 ############# -->
- <sect1 id="sect1-basics-buffers" xreflabel="Buffers">
- <title>Buffers</title>
+ <sect1 id="sect1-basics-data" xreflabel="Data, Buffers and Events">
+ <title>Data, Buffers and Events</title>
<para>
All streams of data in &GStreamer; are chopped up into chunks that are
passed from a source pad on one element to a sink pad on another element.
- <emphasis>Buffers</emphasis> are structures used to hold these chunks of
- data. Buffers can be of any size, theoretically, and they may contain any
- sort of data that the two linked pads know how to handle. Normally, a
- buffer contains a chunk of some sort of audio or video data that flows
- from one element to another.
+ <emphasis>Data</emphasis> are structures used to hold these chunks of
+ data.
+ </para>
+ <para>
+ Data contains the following important types:
+ <itemizedlist>
+ <listitem>
+ <para>
+ An exact type indicating what type of data (control, content, ...)
+ this Data is.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ A reference count indicating the number of elements currently
+ holding a reference to the buffer. When the buffer reference count
+ falls to zero, the buffer will be unlinked, and its memory will be
+ freed in some sense (see below for more details).
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ There are two types of data defined: events (control) and buffers
+ (content).
+ </para>
+ <para>
+ Buffers may contain any sort of data that the two linked pads
+ know how to handle. Normally, a buffer contains a chunk of some sort of
+ audio or video data that flows from one element to another.
</para>
<para>
Buffers also contain metadata describing the buffer's contents. Some of
</listitem>
<listitem>
<para>
- A <classname>GstData</classname> object describing the type of the
- buffer's data.
+ A timestamp indicating the preferred display timestamp of the
+ content in the buffer.
</para>
</listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ Events
+ contain information on the state of the stream flowing between the two
+ linked pads. Events will only be sent if the element explicitely supports
+ them, else the core will (try to) handle the events automatically. Events
+ are used to indicate, for example, a clock discontinuity, the end of a
+ media stream or that the cache should be flushed.
+ </para>
+ <para>
+ Events may contain several of the following items:
+ <itemizedlist>
<listitem>
<para>
- A reference count indicating the number of elements currently
- holding a reference to the buffer. When the buffer reference count
- falls to zero, the buffer will be unlinked, and its memory will be
- freed in some sense (see below for more details).
+ A subtype indicating the type of the contained event.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ The other contents of the event depend on the specific event type.
</para>
</listitem>
</itemizedlist>
<para>
See the &GstLibRef; for the current implementation details of a <ulink
type="http"
- url="../gstreamer/gstreamer-gstbuffer.html"><classname>GstBuffer</classname></ulink>.
+ url="../gstreamer/gstreamer-gstdata.html"><classname>GstData</classname></ulink>, <ulink type="http"
+ url="../gstreamer/gstreamer-gstbuffer.html"><classname>GstBuffer</classname></ulink> and <ulink type="http"
+ url="../gstreamer/gstreamer-gstevent.html"><classname>GstEvent</classname></ulink>.
</para>
<sect2 id="sect2-buffers-bufferpools" xreflabel="Buffer Allocation and
<para>
To improve the latency in a media pipeline, many &GStreamer; elements
use a <emphasis>buffer pool</emphasis> to handle buffer allocation and
- unlinking. A buffer pool is a relatively large chunk of memory that is
- the &GStreamer; process requests early on from the operating system.
- Later, when elements request memory for a new buffer, the buffer pool
- can serve the request quickly by giving out a piece of the allocated
- memory. This saves a call to the operating system and lowers latency.
- [If it seems at this point like &GStreamer; is acting like an operating
- system (doing memory management, etc.), don't worry: &GStreamer;OS isn't
- due out for quite a few years!]
+ releasing. A buffer pool is a virtual representation of one or more
+ buffers of which the data is not actually allocated by &GStreamer;
+ itself. Examples of these include hardware framebuffer memory in video
+ output elements or kernel-allocated DMA memory for video capture. The
+ huge advantage of using these buffers instead of creating our own is
+ that we do not have to copy memory from one place to another, thereby
+ saving a noticeable number of CPU cycles. Elements should not provide
+ a bufferpool to decrease the number of memory allocations: the kernel
+ will generally take care of that - and will probably do that much more
+ efficiently than we ever could. Using bufferpools in this way is highly
+ discouraged.
</para>
<para>
Normally in a media pipeline, most filter elements in &GStreamer; deal
<!-- ############ sect1 ############# -->
<sect1 id="sect1-basics-types" xreflabel="Types and Properties">
- <title>Types and Properties</title>
+ <title>Mimetypes and Properties</title>
<para>
&GStreamer; uses a type system to ensure that the data passed between
- elements is in a recognized format. The type system is also important for
- ensuring that the parameters required to fully specify a format match up
- correctly when linking pads between elements. Each link that is
- made between elements has a specified type.
+ elements is in a recognized format. The type system is also important
+ for ensuring that the parameters required to fully specify a format match
+ up correctly when linking pads between elements. Each link that is
+ made between elements has a specified type and optionally a set of
+ properties.
</para>
<!-- ############ sect2 ############# -->
<title>The Basic Types</title>
<para>
&GStreamer; already supports many basic media types. Following is a
- table of the basic types used for buffers in &GStreamer;. The table
- contains the name ("mime type") and a description of the type, the
- properties associated with the type, and the meaning of each property.
+ table of a few of the the basic types used for buffers in
+ &GStreamer;. The table contains the name ("mime type") and a
+ description of the type, the properties associated with the type, and
+ the meaning of each property. A full list of supported types is
+ included in <xref linkend="sect1-types-definitions"/>.
</para>
<table frame="all" id="table-basictypes" xreflabel="Table of Basic Types">
<!-- ############ type ############# -->
<row>
- <entry morerows="10">audio/raw</entry>
- <entry morerows="10">
- Unstructured and uncompressed raw audio data.
+ <entry morerows="1">audio/*</entry>
+ <entry morerows="1">
+ <emphasis>All audio types</emphasis>
</entry>
<entry>rate</entry>
<entry>integer</entry>
<entry>greater than 0</entry>
<entry>
- The sample rate of the data, in samples per second.
+ The sample rate of the data, in samples (per channel) per second.
</entry>
</row>
<row>
The number of channels of audio data.
</entry>
</row>
+
+ <!-- ############ type ############# -->
+
<row>
- <entry>format</entry>
- <entry>string</entry>
- <entry><quote>int</quote> or <quote>float</quote></entry>
- <entry>
- The format in which the audio data is passed.
+ <entry morerows="3">audio/x-raw-int</entry>
+ <entry morerows="3">
+ Unstructured and uncompressed raw integer audio data.
</entry>
- </row>
- <row>
- <entry>law</entry>
- <entry>integer</entry>
- <entry>0, 1, or 2</entry>
- <entry>
- (Valid only if the data is in integer format.) The law used to
- describe the data. The value 0 indicates <quote>linear</quote>, 1
- indicates <quote>mu law</quote>, and 2 indicates
- <quote>A law</quote>.
- </entry>
- </row>
- <row>
<entry>endianness</entry>
- <entry>boolean</entry>
- <entry>0 or 1</entry>
+ <entry>integer</entry>
+ <entry>G_BIG_ENDIAN (1234) or G_LITTLE_ENDIAN (4321)</entry>
<entry>
- (Valid only if the data is in integer format.) The order of bytes
- in a sample. The value 0 means <quote>little-endian</quote> (bytes
- are least significant first). The value 1 means
- <quote>big-endian</quote> (most significant byte first).
+ The order of bytes in a sample. The value G_LITTLE_ENDIAN (4321)
+ means <quote>little-endian</quote> (byte-order is <quote>least
+ significant byte first</quote>). The value G_BIG_ENDIAN (1234)
+ means <quote>big-endian</quote> (byte order is <quote>most
+ significant byte first</quote>).
</entry>
</row>
<row>
<entry>signed</entry>
<entry>boolean</entry>
- <entry>0 or 1</entry>
+ <entry>TRUE or FALSE</entry>
<entry>
- (Valid only if the data is in integer format.) Whether the samples
- are signed or not.
+ Whether the values of the integer samples are signed or not.
+ Signed samples use one bit to indicate sign (negative or
+ positive) of the value. Unsigned samples are always positive.
</entry>
</row>
<row>
<entry>integer</entry>
<entry>greater than 0</entry>
<entry>
- (Valid only if the data is in integer format.) The number of bits
- per sample.
+ Number of bits allocated per sample.
</entry>
</row>
<row>
<entry>integer</entry>
<entry>greater than 0</entry>
<entry>
- (Valid only if the data is in integer format.) The number of bits
- used per sample. This must be less than or equal to the width: If
- the depth is less than the width, the low bits are assumed to be
- the ones used. For example, a width of 32 and a depth of 24 means
- that each sample is stored in a 32 bit word, but only the low 24
- bits are actually used.
- </entry>
- </row>
- <row>
- <entry>layout</entry>
- <entry>string</entry>
- <entry><quote>gfloat</quote></entry>
- <entry>
- (Valid only if the data is in float format.) A string representing
- the way in which the floating point data is represented.
+ The number of bits used per sample. This must be less than or
+ equal to the width: If the depth is less than the width, the
+ low bits are assumed to be the ones used. For example, a width
+ of 32 and a depth of 24 means that each sample is stored in a
+ 32 bit word, but only the low 24 bits are actually used.
</entry>
</row>
+
+ <!-- ############ type ############# -->
+
<row>
- <entry>intercept</entry>
- <entry>float</entry>
- <entry>any, normally 0</entry>
- <entry>
- (Valid only if the data is in float format.) A floating point
- value representing the value that the signal
- <quote>centers</quote> on.
+ <entry morerows="3">audio/mpeg</entry>
+ <entry morerows="3">
+ Audio data compressed using the MPEG audio encoding scheme.
</entry>
- </row>
- <row>
- <entry>slope</entry>
- <entry>float</entry>
- <entry>any, normally 1.0</entry>
+ <entry>mpegversion</entry>
+ <entry>integer</entry>
+ <entry>1, 2 or 4</entry>
<entry>
- (Valid only if the data is in float format.) A floating point
- value representing how far the signal deviates from the intercept.
- A slope of 1.0 and an intercept of 0.0 would mean an audio signal
- with minimum and maximum values of -1.0 and 1.0. A slope of
- 0.5 and intercept of 0.5 would represent values in the range 0.0
- to 1.0.
+ The MPEG-version used for encoding the data. The value 1 refers
+ to MPEG-1, -2 and -2.5 layer 1, 2 or 3. The values 2 and 4 refer
+ to the MPEG-AAC audio encoding schemes.
</entry>
</row>
-
- <!-- ############ type ############# -->
-
<row>
- <entry morerows="4">audio/mp3</entry>
- <entry morerows="4">
- Audio data compressed using the mp3 encoding scheme.
- </entry>
<entry>framed</entry>
<entry>boolean</entry>
<entry>0 or 1</entry>
<entry>integer</entry>
<entry>1, 2, or 3</entry>
<entry>
- The compression scheme layer used to compress the data.
+ The compression scheme layer used to compress the data
+ <emphasis>(only if mpegversion=1)</emphasis>.
</entry>
</row>
<row>
<entry>integer</entry>
<entry>greater than 0</entry>
<entry>
- The bitrate, in kilobits per second. For VBR (variable bitrate)
- mp3 data, this is the average bitrate.
- </entry>
- </row>
- <row>
- <entry>channels</entry>
- <entry>integer</entry>
- <entry>greater than 0</entry>
- <entry>
- The number of channels of audio data present.
- </entry>
- </row>
- <row>
- <entry>joint-stereo</entry>
- <entry>boolean</entry>
- <entry>0 or 1</entry>
- <entry>
- If true, this implies that stereo data is stored as a combined
- signal and the difference between the signals, rather than as two
- entirely separate signals. If true, the <quote>channels</quote>
- attribute must not be zero.
+ The bitrate, in bits per second. For VBR (variable bitrate)
+ MPEG data, this is the average bitrate.
</entry>
</row>
<!-- ############ type ############# -->
<row>
- <entry morerows="0">audio/x-ogg</entry>
- <entry morerows="0">
- Audio data compressed using the Ogg Vorbis encoding scheme.
- </entry>
+ <entry>audio/x-vorbis</entry>
+ <entry>Vorbis audio data</entry>
<entry></entry>
<entry></entry>
<entry></entry>
<entry>
- FIXME: There are currently no parameters defined for this type.
- </entry>
- </row>
-
- <!-- ############ type ############# -->
-
- <row>
- <entry morerows="2">video/raw</entry>
- <entry morerows="2">
- Raw video data.
- </entry>
- <entry>fourcc</entry>
- <entry>FOURCC code</entry>
- <entry></entry>
- <entry>
- A FOURCC code identifying the format in which this data is stored.
- FOURCC (Four Character Code) is a simple system to allow
- unambiguous identification of a video datastream format. See
- <ulink url="http://www.webartz.com/fourcc/"
- type="http">http://www.webartz.com/fourcc/</ulink>
+ There are currently no specific properties defined for this type.
</entry>
</row>
- <row>
- <entry>width</entry>
- <entry>integer</entry>
- <entry>greater than 0</entry>
- <entry>
- The number of pixels wide that each video frame is.
- </entry>
- </row>
- <row>
- <entry>height</entry>
- <entry>integer</entry>
- <entry>greater than 0</entry>
- <entry>
- The number of pixels high that each video frame is.
- </entry>
- </row>
-
- <!-- ############ type ############# -->
-
- <row>
- <entry morerows="0">video/mpeg</entry>
- <entry morerows="0">
- Video data compressed using an MPEG encoding scheme.
- </entry>
- <entry></entry>
- <entry></entry>
- <entry></entry>
- <entry>
- FIXME: There are currently no parameters defined for this type.
- </entry>
- </row>
-
- <!-- ############ type ############# -->
-
- <row>
- <entry morerows="0">video/x-msvideo</entry>
- <entry morerows="0">
- Video data compressed using the AVI encoding scheme.
- </entry>
- <entry></entry>
- <entry></entry>
- <entry></entry>
- <entry>
- FIXME: There are currently no parameters defined for this type.
- </entry>
- </row>
-
</tbody>
</tgroup>
</table>
</sect2>
</sect1>
-
- <!-- ############ sect1 ############# -->
-
- <sect1 id="sect1-basics-events" xreflabel="Events">
- <title>Events</title>
- <para>
- Sometimes elements in a media processing pipeline need to know that
- something has happened. An <emphasis>event</emphasis> is a special type of
- data in &GStreamer; designed to serve this purpose. Events describe some
- sort of activity that has happened somewhere in an element's pipeline, for
- example, the end of the media stream or a clock discontinuity. Just like
- any other data type, an event comes to an element on a sink pad and is
- contained in a normal buffer. Unlike normal stream buffers, though, an
- event buffer contains only an event, not any media stream data.
- </para>
- <para>
- See the &GstLibRef; for the current implementation details of a <ulink
- type="http"
- url="../gstreamer/gstreamer-gstevent.html"><classname>GstEvent</classname></ulink>.
- </para>
- </sect1>
</chapter>
The remainder of this introductory part of the guide presents a short
overview of the basic concepts involved in &GStreamer; plugin development.
Topics covered include <xref linkend="sect1-basics-elements"/>, <xref
- linkend="sect1-basics-pads"/>, <xref linkend="sect1-basics-buffers"/>,
- <xref linkend="sect1-basics-types"/>, and <xref
- linkend="sect1-basics-events"/>. If you are already familiar with this
- information, you can use this short overview to refresh your memory, or
- you can skip to <xref linkend="part-building"/>.
+ linkend="sect1-basics-pads"/>, <xref linkend="sect1-basics-data"/> and
+ <xref linkend="sect1-basics-types"/>. If you are already familiar with
+ this information, you can use this short overview to refresh your memory,
+ or you can skip to <xref linkend="part-building"/>.
</para>
<para>
As you can see, there a lot to learn, so let's get started!
<!ENTITY APPENDIX_PYTHON SYSTEM "appendix_python.xml">
<!ENTITY GStreamer "<application>GStreamer</application>">
-<!ENTITY GstVersion "0.4.2.2">
+<!ENTITY GstVersion "0.7.4">
<!ENTITY GstAppDevMan "<emphasis>GStreamer Application Development Manual</emphasis>">
<!ENTITY GstLibRef "<emphasis>GStreamer Library Reference</emphasis>">
]>
</para>
</authorblurb>
</author>
+
+ <author>
+ <firstname>Ronald</firstname>
+ <othername>S.</othername>
+ <surname>Bultje</surname>
+ <authorblurb>
+ <para>
+ <email>rbultje@ronald.bitfreak.net</email>
+ </para>
+ </authorblurb>
+ </author>
</authorgroup>
<legalnotice id="legalnotice">
projects / platform / upstream / gstreamer.git / commitdiff