Only warn about "Invalid and inefficient vfw-avi packed B frames" once.

Patch by Andrew Savchenko, Bircoph at list dot ru

Originally committed as revision 15772 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h263.c

@@ -5751,8 +5751,10 @@ 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)
+        if(s->divx_packed && !s->showed_packed_warning) {
             av_log(s->avctx, AV_LOG_WARNING, "Invalid and inefficient vfw-avi packed B frames detected\n");
+            s->showed_packed_warning=1;
+        }
     }
 
     /* ffmpeg detection */

libavcodec/mpegvideo.h

@@ -487,6 +487,7 @@ typedef struct MpegEncContext {
     /* H.263 specific */
     int gob_index;
     int obmc;                       ///< overlapped block motion compensation
+    int showed_packed_warning;      ///< flag for having shown the warning about divxs invalid b frames
 
     /* H.263+ specific */
     int umvplus;                    ///< == H263+ && unrestricted_mv