lavf: cdg has large non keyframe segments and should thus be exempt from the...

lavf: cdg has large non keyframe segments and should thus be exempt from the non keyframe check in seeking.
Improves seeking for cdg files.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -1823,7 +1823,7 @@ static int seek_frame_generic(AVFormatContext *s,
             if(stream_index == pkt.stream_index && pkt.dts > timestamp){
                 if(pkt.flags & AV_PKT_FLAG_KEY)
                     break;
-                if(nonkey++ > 1000){
+                if(nonkey++ > 1000 && st->codec->codec_id != CODEC_ID_CDGRAPHICS){
                     av_log(s, AV_LOG_ERROR,"seek_frame_generic failed as this stream seems to contain no keyframes after the target timestamp, %d non keyframes found\n", nonkey);
                     break;
                 }