remove unneeded assignment in inner loop. rematrixing bands are contiguous.

Originally committed as revision 20089 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ac3dec.c

@@ -608,10 +608,11 @@ static void do_rematrixing(AC3DecodeContext *s)
 
     end = FFMIN(s->end_freq[1], s->end_freq[2]);
 
+    i = ff_ac3_rematrix_band_tab[0];
     for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
         if(s->rematrixing_flags[bnd]) {
             bndend = FFMIN(end, ff_ac3_rematrix_band_tab[bnd+1]);
-            for(i=ff_ac3_rematrix_band_tab[bnd]; i<bndend; i++) {
+            for(; i<bndend; i++) {
                 tmp0 = s->fixed_coeffs[1][i];
                 tmp1 = s->fixed_coeffs[2][i];
                 s->fixed_coeffs[1][i] = tmp0 + tmp1;