avformat/mpegts: consider stream_type 4 just a hint toward mp3 and not definite

Fixes Ticket 4864
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mpegts.c

@@ -803,6 +803,8 @@ static int mpegts_set_stream_info(AVStream *st, PESContext *pes,
     st->codec->codec_tag = pes->stream_type;
 
     mpegts_find_stream_type(st, pes->stream_type, ISO_types);
+    if (pes->stream_type == 4)
+        st->request_probe = 50;
     if ((prog_reg_desc == AV_RL32("HDMV") ||
          prog_reg_desc == AV_RL32("HDPR")) &&
         st->codec->codec_id == AV_CODEC_ID_NONE) {