[SCM] libav/experimental: Correct pulse amplitude application - a negative or 0 coefficient implies the pulse is subtracted, else it is added. Also avoid a divide by 0.

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit febcbd65fa3d00cfdfbfabd1c2a8fb8e659e1ca1
Author: Robert Swain <robert.swain at gmail.com>
Date:   Thu Sep 11 01:22:34 2008 +0000

    Correct pulse amplitude application - a negative or 0 coefficient implies the
    pulse is subtracted, else it is added. Also avoid a divide by 0.
    
    Based on a patch by Alex Converse (alex converse gmail com)
    Fixes part of issue632
    
    Originally committed as revision 15294 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/aac.c b/libavcodec/aac.c
index c59a663..cc069ed 100644
--- a/libavcodec/aac.c
+++ b/libavcodec/aac.c
@@ -753,7 +753,9 @@ static int decode_spectrum_and_dequant(AACContext * ac, float coef[1024], GetBit
     if (pulse_present) {
         for(i = 0; i < pulse->num_pulse; i++){
             float co  = coef_base[ pulse->pos[i] ];
-            float ico = co / sqrtf(sqrtf(fabsf(co))) + pulse->amp[i];
+            float ico = -pulse->amp[i];
+            if (co)
+                ico = co / sqrtf(sqrtf(fabsf(co))) + (co > 0 ? -ico : ico);
             coef_base[ pulse->pos[i] ] = cbrtf(fabsf(ico)) * ico;
         }
     }

-- 
Libav/FFmpeg packaging