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

[Devin Heitmueller]

Hello Aman,

On Thu, May 17, 2018 at 8:04 PM, Aman Gupta <ffmpeg at tmm1.net> wrote:
> 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.

I guess my big question would be, why is the ffmpeg TS demux
interpreting some PIDs as containing PMT if they are not referenced by
the PAT?  I have to assume there is some heuristic in there which
looks at arbitrary PID data and attempts to treat it as a PMT table
(presumably in an attempt to play TS streams which are missing PAT).
If that's the case, then I think *that's* what the patch should
disable - assume the PAT/PMT are present and well-formed and don't
play games trying to find a PMT assuming the PAT is absent/malformed.

I can appreciate a player doing it's best to play some screwed up
stream, but that sort of logic should not be the default.  There are
all sorts of strange proprietary data sent by broadcasters over PIDs
and I wouldn't want those to get mis-detected as PMT when the spec
says PIDs not explicitly in the PAT/PMT should be completely ignored.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com