mpegts: Attempt to seek back to beginning in non-seekable mpegts files.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegts.c

@@ -1563,7 +1563,10 @@ static int mpegts_read_header(AVFormatContext *s,
         /* normal demux */
 
         /* first do a scaning to get all the services */
-        if (pb->seekable && avio_seek(pb, pos, SEEK_SET) < 0)
+        /* NOTE: We attempt to seek on non-seekable files as well, as the
+         * probe buffer usually is big enough. Only warn if the seek failed
+         * on files where the seek should work. */
+        if (avio_seek(pb, pos, SEEK_SET) < 0)
             av_log(s, AV_LOG_ERROR, "Unable to seek back to the start\n");
 
         mpegts_open_section_filter(ts, SDT_PID, sdt_cb, ts, 1);