[FFmpeg-devel] [PATCH 1/2] avformat/mpegts: parse sections with multiple tables

[Michael Niedermayer]

On Wed, May 09, 2018 at 02:35:00PM -0700, Aman Gupta wrote:
> From: Aman Gupta <aman at tmm1.net>
> 
> Fixes PMT parsing in some mpegts streams which contain
> multiple tables within the PMT pid. Previously, the parser
> assumed only one table was present in each packet, and discarded
> the rest of the section data after attempting to parse the first
> table.
> 
> A similar issue was documented in the BeyondTV software[1], which
> helped me diagnose the same bug in the ffmpeg mpegts demuxer. I also
> tried DVBInspector, libdvbpsi's dvbinfo, and tstools' tsinfo to
> help debug. The former two properly read PMTs with multiple tables,
> whereas the last has the same bug as ffmpeg.
> 
> I've created a minimal sample[2] which contains the combined PMT.
> Here's what ffmpeg probe shows before and after this patch:
> 
> Before:
> 
>     Input #0, mpegts, from 'combined-pmt-tids.ts':
>       Duration: 00:00:01.08, start: 4932.966167, bitrate: 741 kb/s
>       Program 1
>       No Program
>         Stream #0:0[0xf9d]: Audio: ac3, 48000 Hz, mono, fltp, 96 kb/s
>         Stream #0:1[0xf9b]: Audio: mp3, 0 channels, fltp
>         Stream #0:2[0xf9c]: Unknown: none
> 
> After:
> 
>     Input #0, mpegts, from 'combined-pmt-tids.ts':
>       Duration: 00:00:01.11, start: 4932.966167, bitrate: 718 kb/s
>       Program 1
>         Stream #0:0[0xf9b]: Video: mpeg2video ([2][0][0][0] / 0x0002), none(tv, top first), 29.97 fps, 29.97 tbr, 90k tbn, 90k tbc
>         Stream #0:1[0xf9c](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, 5.1(side), fltp, 384 kb/s
>         Stream #0:2[0xf9d](spa): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, mono, fltp, 96 kb/s
> 
> With the patch, the PMT is parsed correctly so the streams are
> created in the correct order, are associated with "Program 1",
> and their codecs are set correctly.
> 
> [1] http://forums.snapstream.com/vb/showpost.php?p=343816&postcount=201
> [2] https://s3.amazonaws.com/tmm1/combined-pmt-tids.ts
> 
> Signed-off-by: Aman Gupta <aman at tmm1.net>
> ---
>  libavformat/mpegts.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)

probably ok.

The code looks a bit convoluted, so testing with a fuzzer probably wont hurt

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

It is dangerous to be right in matters on which the established authorities
are wrong. -- Voltaire
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