Only try to probe the codec when the available data has roughly doubled

relative to the last attempt.

Originally committed as revision 14188 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/utils.c

@@ -588,11 +588,13 @@ int av_read_packet(AVFormatContext *s, AVPacket *pkt)
             pd->buf_size += pkt->size;
             memset(pd->buf+pd->buf_size, 0, AVPROBE_PADDING_SIZE);
 
+            if(av_log2(pd->buf_size) != av_log2(pd->buf_size - pkt->size)){
             set_codec_from_probe_data(st, pd, 1);
             if(st->codec->codec_id != CODEC_ID_PROBE){
                 pd->buf_size=0;
                 av_freep(&pd->buf);
             }
+            }
         }
     }
 }