Change sign in ff_celp_lp_synthesis_filterf(). This makes this function

useful for AMR and RA144.

Patch by Kenan Gillet

Originally committed as revision 17546 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/celp_filters.c

@@ -102,6 +102,6 @@ void ff_celp_lp_synthesis_filterf(
     {
         out[n] = in[n];
         for(i=1; i<filter_length; i++)
-            out[n] += filter_coeffs[i] * out[n-i];
+            out[n] -= filter_coeffs[i] * out[n-i];
     }
 }