[FFmpeg-devel] [PATCH] avformat/mpegts: add skip_unknown_pmt option

Aman Gupta ffmpeg at tmm1.net
Fri May 18 03:04:44 EEST 2018


From: Aman Gupta <aman at tmm1.net>

Some filtered mpegts streams may erroneously include PMTs for programs
that are not advertised in the PAT. This confuses ffmpeg and most
players because multiple audio/video streams are created and it is
unclear which ones actually contain data.

See for example https://tmm1.s3.amazonaws.com/unknown-pmts.ts

Before:

    Input #0, mpegts, from 'unknown-pmts.ts':
      Duration: 00:00:10.11, start: 80741.189700, bitrate: 9655 kb/s
      Program 4
        Stream #0:2[0x41]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 11063 kb/s, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
        Stream #0:3[0x44](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 384 kb/s
        Stream #0:4[0x45](spa): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 128 kb/s
      No Program
        Stream #0:0[0x31]: Video: mpeg2video ([2][0][0][0] / 0x0002), none(tv), 90k tbr, 90k tbn, 90k tbc
        Stream #0:1[0x34](eng): Audio: ac3 (AC-3 / 0x332D4341), 0 channels, fltp
        Stream #0:5[0x51]: Video: mpeg2video ([2][0][0][0] / 0x0002), none, 90k tbr, 90k tbn
        Stream #0:6[0x54](eng): Audio: ac3 (AC-3 / 0x332D4341), 0 channels

With skip_unknown_pmt=1:

    Input #0, mpegts, from 'unknown-pmts.ts':
      Duration: 00:00:10.11, start: 80741.189700, bitrate: 9655 kb/s
      Program 4
        Stream #0:0[0x41]: Video: mpeg2video (Main) ([2][0][0][0] / 0x0002), yuv420p(tv, bt709, progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 11063 kb/s, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
        Stream #0:1[0x44](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 384 kb/s
        Stream #0:2[0x45](spa): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 128 kb/s

Signed-off-by: Aman Gupta <aman at tmm1.net>
---
 doc/demuxers.texi    | 3 +++
 libavformat/mpegts.c | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/doc/demuxers.texi b/doc/demuxers.texi
index e7c2abce57..1d2ee5bf37 100644
--- a/doc/demuxers.texi
+++ b/doc/demuxers.texi
@@ -538,6 +538,9 @@ This demuxer accepts the following options:
 Set size limit for looking up a new synchronization. Default value is
 65536.
 
+ at item skip_unknown_pmt
+Skip PMTs for programs not defined in the PAT. Default value is 0.
+
 @item fix_teletext_pts
 Override teletext packet PTS and DTS values with the timestamps calculated
 from the PCR of the first program which the teletext stream is part of and is
diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
index fc9bb3940e..18df1afd9d 100644
--- a/libavformat/mpegts.c
+++ b/libavformat/mpegts.c
@@ -143,6 +143,7 @@ struct MpegTSContext {
 
     int skip_changes;
     int skip_clear;
+    int skip_unknown_pmt;
 
     int scan_all_pmts;
 
@@ -172,6 +173,8 @@ static const AVOption options[] = {
      {.i64 = 0}, 0, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_EXPORT | AV_OPT_FLAG_READONLY },
     {"scan_all_pmts", "scan and combine all PMTs", offsetof(MpegTSContext, scan_all_pmts), AV_OPT_TYPE_BOOL,
      {.i64 = -1}, -1, 1, AV_OPT_FLAG_DECODING_PARAM },
+    {"skip_unknown_pmt", "skip PMTs for programs not advertised in the PAT", offsetof(MpegTSContext, skip_unknown_pmt), AV_OPT_TYPE_BOOL,
+     {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
     {"skip_changes", "skip changing / adding streams / programs", offsetof(MpegTSContext, skip_changes), AV_OPT_TYPE_BOOL,
      {.i64 = 0}, 0, 1, 0 },
     {"skip_clear", "skip clearing programs", offsetof(MpegTSContext, skip_clear), AV_OPT_TYPE_BOOL,
@@ -2028,6 +2031,8 @@ static void pmt_cb(MpegTSFilter *filter, const uint8_t *section, int section_len
     if (!ts->scan_all_pmts && ts->skip_changes)
         return;
 
+    if (ts->skip_unknown_pmt && !get_program(ts, h->id))
+        return;
     if (!ts->skip_clear)
         clear_program(ts, h->id);
 
-- 
2.14.2



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