It appears s->bitstream_buffer_size has to be 0 at the end so rather use assert.

Originally committed as revision 20996 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263dec.c

@@ -667,8 +667,9 @@ retry:
             s->error_status_table[s->mb_num-1]= AC_ERROR|DC_ERROR|MV_ERROR;
         }
 
+    assert(s->bitstream_buffer_size==0);
     /* divx 5.01+ bistream reorder stuff */
-    if(s->codec_id==CODEC_ID_MPEG4 && s->bitstream_buffer_size==0 && s->divx_packed){
+    if(s->codec_id==CODEC_ID_MPEG4 && s->divx_packed){
         int current_pos= get_bits_count(&s->gb)>>3;
         int startcode_found=0;