Warn about packed B-frames. (especially useful if the file in question is

not an avi ...)

Originally committed as revision 13428 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263.c

@@ -5751,6 +5751,8 @@ static int decode_user_data(MpegEncContext *s, GetBitContext *gb){
         s->divx_version= ver;
         s->divx_build= build;
         s->divx_packed= e==3 && last=='p';
+        if(s->divx_packed)
+            av_log(s->avctx, AV_LOG_WARNING, "Invalid and inefficient vfw-avi packed B frames detected\n");
     }
 
     /* ffmpeg detection */