[SCM] libav/experimental: vorbisdec: Fix floor1 decoding

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit 8455e8c7c0ad183e8904e583def669ba4b7b4c90
Author: Gregory Maxwell <greg at xiph.org>
Date:   Fri Nov 12 04:33:26 2010 +0000

    vorbisdec: Fix floor1 decoding
    
    An intermediate value in the floor 1 linear interpolation was
    overflowing
    resulting in obvious artifacts on some files.
    
    e.g.
    http://upload.wikimedia.org/wikipedia/commons/7/79/Big_Buck_Bunny_small.ogv
    
    Prior to this fix 87 out of 128 64kbit/s mono files decoded with ffmpeg
    have
    lower PEAQ ODG values than the same files decoded with libvorbis. With
    this
    fix none of that set have significantly worse ODG values than libvorbis.
    
    Fixes issue 2352
    
    Patch by Gregory Maxwell <greg at xiph.org>
    
    Originally committed as revision 25724 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/vorbis_dec.c b/libavcodec/vorbis_dec.c
index c209912..284b8df 100644
--- a/libavcodec/vorbis_dec.c
+++ b/libavcodec/vorbis_dec.c
@@ -1146,8 +1146,8 @@ static int vorbis_floor1_decode(vorbis_context *vc,
     int_fast16_t book;
     uint_fast16_t offset;
     uint_fast16_t i,j;
-    /*u*/int_fast16_t adx, ady, off, predicted; // WTF ? dy/adx =  (unsigned)dy/adx ?
-    int_fast16_t dy, err;
+    int_fast16_t adx, ady, dx, off, predicted;
+    int_fast32_t err;
 
 
     if (!get_bits1(gb)) // silence
@@ -1210,7 +1210,7 @@ static int vorbis_floor1_decode(vorbis_context *vc,
         adx = vf->list[high_neigh_offs].x - vf->list[low_neigh_offs].x;
         ady = FFABS(dy);
         err = ady * (vf->list[i].x - vf->list[low_neigh_offs].x);
-        off = (int16_t)err / (int16_t)adx;
+        off = err / adx;
         if (dy < 0) {
             predicted = floor1_Y_final[low_neigh_offs] - off;
         } else {

-- 
Libav/FFmpeg packaging