Corrections from Tor-Einar Jarnbjo added to spec

svn path=/trunk/vorbis/; revision=4004

diff --git a/doc/vorbis-spec-floor1.html b/doc/vorbis-spec-floor1.html
index 1c53738..a81c210 100644 (file)
--- a/doc/vorbis-spec-floor1.html
+++ b/doc/vorbis-spec-floor1.html
@@ -6,7 +6,7 @@
 Ogg Vorbis I format specification: floor type 1 setup and decode
 </font></h1>
 
-<em>Last update to this document: September 19, 2002</em><br>
+<em>Last update to this document: October 15, 2002</em><br>
 
 <h1>Overview</h1>
 
@@ -247,8 +247,8 @@ Unwrap the always-positive-or-zero values read from the packet into
        8) [high_neighbor_offset] = <a href="helper.html#high_neighbor">high_neighbor</a>([floor1_X_list],[i])
 
        9) [predicted] = <a href="helper.html#render_point">render_point</a>( vector [floor1_X_list] element [low_neighbor_offset],
-                                      vector [floor1_X_list] element [high_neighbor_offset],
                                      vector [floor1_final_Y] element [low_neighbor_offset],
+                                      vector [floor1_X_list] element [high_neighbor_offset],
                                      vector [floor1_final_Y] element [high_neighbor_offset],
                                       vector [floor1_X_list] element [i] )
 
@@ -278,7 +278,7 @@ Unwrap the always-positive-or-zero values read from the packet into
                     
                      } else [hiroom] is not greater than [lowroom] {
               
-                        23) vector [floor1_final_Y] element [i] = [predicted] - ([val] - [lowroom]) - 1
+                        23) vector [floor1_final_Y] element [i] = [predicted] - [val] + [hiroom] - 1
                    
                       }
                
@@ -287,7 +287,7 @@ Unwrap the always-positive-or-zero values read from the packet into
                  24) if ([val] is odd) {
                  
                         25) vector [floor1_final_Y] element [i] = 
-                            [predicted] - (([val] - 1) divided by  2 using integer division)
+                            [predicted] - (([val] + 1) divided by  2 using integer division)
 
                       } else [val] is even {
 
@@ -342,22 +342,22 @@ Then compute the final curve in one pass:<p>
 
              6) [hy] = [floor1_final_Y]' element [i] * [floor1_multiplier]
             7) [hx] = [floor1_X_list]' element [i]
-             8) <a href="helper.html#render_line">render_line</a>( [lx], [hx], [ly], [hy], [floor] )
+             8) <a href="helper.html#render_line">render_line</a>( [lx], [ly], [hx], [hy], [floor] )
              9) [lx] = [hx]
            10) [ly] = [hy]
           }
+     }
  
-      11) if ( [hx] is less than [n] ) {
+ 11) if ( [hx] is less than [n] ) {
 
-            12) <a href="helper.html#render_line">render_line</a>( [hx], [hy], [n], [hy], [floor] )
+       12) <a href="helper.html#render_line">render_line</a>( [hx], [hy], [n], [hy], [floor] )
 
-          }
+     }
 
-      13) if ( [hx] is greater than [n] ) {
+ 13) if ( [hx] is greater than [n] ) {
 
-            14) truncate vector [floor] to [n] elements
+       14) truncate vector [floor] to [n] elements
 
-          }
      }
  
  15) for each scalar in vector [floor], perform a lookup substitution using 

diff --git a/doc/vorbis-spec-ref.html b/doc/vorbis-spec-ref.html
index 923fe85..c52b9e7 100644 (file)
--- a/doc/vorbis-spec-ref.html
+++ b/doc/vorbis-spec-ref.html
@@ -168,15 +168,18 @@ uses a single mapping type (0), with implicit PCM channel mappings.<p>
              <ol><li>if set, <tt>[vorbis_mapping_submaps]</tt> = read 4 bits as unsigned integer and add one<p>
                  <li>if unset, <tt>[vorbis_mapping_submaps]</tt> = 1<p>
              </ol>
-          <li>read 1 bit as a boolean flag; if set, square polar channel mapping is in use:<p>
-              <ol><li><tt>[vorbis_mapping_coupling_steps]</tt>= read 8 bits as unsigned integer and add one<p>
-                  <li>for <tt>[j]</tt> each of <tt>[vorbis_mapping_coupling_steps]</tt> steps:<p>
-                      <ol>
-                      <li>vector <tt>[vorbis_mapping_magnitude]</tt> element <tt>[j]</tt>= read <a href="helper.html#ilog">ilog</a>([audio_channels] - 1) bits as unsigned integer<p>
-                      <li>vector <tt>[vorbis_mapping_angle]</tt> element <tt>[j]</tt>= read <a href="helper.html#ilog">ilog</a>([audio_channels] - 1) bits as unsigned integer<p>
-                      <li>the numbers read in the above two steps are channel numbers representing the channel to treat as magnitude and the channel to treat as angle, respectively.  If for any coupling step the angle channel number equals the magnitude channel number, the magnitude channel number is greater than <tt>[audio_channels]</tt>-1, or the angle channel is greater than <tt>[audio_channels]</tt>-1, the stream is undecodable.<p>
-                      </ol>
-               </ol>
+          <li>read 1 bit as a boolean flag<p>
+            <ol><li>if set, square polar channel mapping is in use:<p>
+                  <ol><li><tt>[vorbis_mapping_coupling_steps]</tt> = read 8 bits as unsigned integer and add one<p>
+                      <li>for <tt>[j]</tt> each of <tt>[vorbis_mapping_coupling_steps]</tt> steps:<p>
+                          <ol>
+                          <li>vector <tt>[vorbis_mapping_magnitude]</tt> element <tt>[j]</tt>= read <a href="helper.html#ilog">ilog</a>([audio_channels] - 1) bits as unsigned integer<p>
+                          <li>vector <tt>[vorbis_mapping_angle]</tt> element <tt>[j]</tt>= read <a href="helper.html#ilog">ilog</a>([audio_channels] - 1) bits as unsigned integer<p>
+                          <li>the numbers read in the above two steps are channel numbers representing the channel to treat as magnitude and the channel to treat as angle, respectively.  If for any coupling step the angle channel number equals the magnitude channel number, the magnitude channel number is greater than <tt>[audio_channels]</tt>-1, or the angle channel is greater than <tt>[audio_channels]</tt>-1, the stream is undecodable.<p>
+                          </ol>
+                   </ol>
+               <li>if unset, <tt>[vorbis_mapping_coupling_steps]</tt> = 0
+              </ol>
            <li>read 2 bits (reserved field); if the value is nonzero, the stream is undecodable<p>
            <li>if <tt>[vorbis_mapping_submaps]</tt> is greater than one, we read channel multiplex settings.  For each <tt>[j]</tt> of <tt>[audio_channels]</tt> channels:<p>
                <ol><li>vector <tt>[vorbis_mapping_mux]</tt> element <tt>[j]</tt> = read 4 bits as unsigned integer<p>
@@ -259,9 +262,10 @@ must ignore the packet and not attempt decoding it to audio</em>.
   </ol>
 </ol>
 
-Vorbis windows all use the slope function y=sin(2*PI*sin^2(x/n)),
-but dissimilar lapping requirements can affect overall shape.  Window
-generation proceeds as follows:<p>
+Vorbis windows all use the slope function y=sin( .5 * PI * sin^2( (x+.5) /
+n * PI) ) where n is window size and x ranges 0...n-1, but dissimilar
+lapping requirements can affect overall shape.  Window generation
+proceeds as follows:<p>
 
 <ol>
 <li> <tt>[window_center]</tt> = <tt>[n]</tt> / 2
@@ -289,12 +293,12 @@ generation proceeds as follows:<p>
     </ol>
 <li> window from range 0 ... <tt>[left_window_start]</tt>-1 inclusive is zero
 
-<li> for <tt>[i]</tt> in range <tt>[left_window_start]</tt> ... <tt>[left_window_end]</tt>-1, window(<tt>[i]</tt>) = sin(2*PI*sin^2((<tt>[i]</tt>-<tt>[left_window_start]</tt>+.5)/<tt>[left_n]</tt>*PI/2))
+<li> for <tt>[i]</tt> in range <tt>[left_window_start]</tt> ... <tt>[left_window_end]</tt>-1, window(<tt>[i]</tt>) = sin(.5 * PI * sin^2( (<tt>[i]</tt>-<tt>[left_window_start]</tt>+.5) / <tt>[left_n]</tt> * .5 * PI) )
 
 
 <li> window from range <tt>[left_window_end]</tt> ... <tt>[right_window_start]</tt>-1 inclusive is one
 
-<li> for <tt>[i]</tt> in range <tt>[right_window_start]</tt> ... <tt>[right_window_end]</tt>-1, window(<tt>[i]</tt>) = sin(2*PI*sin^2((<tt>[i]</tt>-<tt>[right_window_start]</tt>+.5)/<tt>[right_n]</tt>*PI/2.+PI/2.))
+<li> for <tt>[i]</tt> in range <tt>[right_window_start]</tt> ... <tt>[right_window_end]</tt>-1, window(<tt>[i]</tt>) = sin(.5 * PI * sin^2( (<tt>[i]</tt>-<tt>[right_window_start]</tt>+.5) / <tt>[right_n]</tt> * .5 * PI/2. + .5 * PI) )
 
 <li> window from range <tt>[rigth_window_start]</tt> ... <tt>[n]</tt>-1 is zero
 

diff --git a/lib/mdct.c b/lib/mdct.c
index 8ab70f4..f98209c 100644 (file)
--- a/lib/mdct.c
+++ b/lib/mdct.c
@@ -12,7 +12,7 @@
 
  function: normalized modified discrete cosine transform
            power of two length transform only [64 <= n ]
- last mod: $Id: mdct.c,v 1.31 2002/06/28 22:19:36 xiphmont Exp $
+ last mod: $Id: mdct.c,v 1.32 2002/10/16 02:43:48 xiphmont Exp $
 
  Original algorithm adapted long ago from _The use of multirate filter
  banks for coding of high quality digital audio_, by T. Sporer,
@@ -26,7 +26,7 @@
 
  This module DOES NOT INCLUDE code to generate/apply the window
  function.  Everybody has their own weird favorite including me... I
- happen to like the properties of y=sin(2PI*sin^2(x)), but others may
+ happen to like the properties of y=sin(.5PI*sin^2(x)), but others may
  vehemently disagree.
 
  ********************************************************************/

diff --git a/lib/window.c b/lib/window.c
index 45e7c24..b2db038 100644 (file)
--- a/lib/window.c
+++ b/lib/window.c
@@ -11,7 +11,7 @@
  ********************************************************************
 
  function: window functions
- last mod: $Id: window.c,v 1.17 2002/03/23 03:17:34 xiphmont Exp $
+ last mod: $Id: window.c,v 1.18 2002/10/16 02:43:48 xiphmont Exp $
 
  ********************************************************************/
 
@@ -26,7 +26,7 @@ float *_vorbis_window(int type, int left){
 
   switch(type){
   case 0:
-    /* The 'vorbis window' (window 0) is sin(sin(x)*sin(x)*2pi) */
+    /* The 'vorbis window' (window 0) is sin(sin(x)*sin(x)*pi*.5) */
     {
     
       for(i=0;i<left;i++){