Re: [FFmpeg-devel] [PATCH] avformat/mpegts: Add -reprobe_stream_if_pmt_es_stream_type_changes option

[Pavel Koshevoy <pkoshevoy-at-gmail.com@ffmpeg.org>]

On Sat, Jun 14, 2025 at 9:24 PM Andreas Rheinhardt <
andreas.rheinhardt@outlook.com> wrote:

> Pavel Koshevoy:
> > Make runtime AVStream.codecpar codec_id updates optional and disabled
> > by default, so that avformat API clients can enable this feature
> explicitly
> > when they add support for runtime codec changes.
> > ---
> >  libavformat/mpegts.c | 8 +++++++-
> >  tests/fate/demux.mak | 2 +-
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> > index deb69a0548..88b1754307 100644
> > --- a/libavformat/mpegts.c
> > +++ b/libavformat/mpegts.c
> > @@ -156,6 +156,8 @@ struct MpegTSContext {
> >      /** to detect seek */
> >      int64_t last_pos;
> >
> > +    int reprobe_stream_if_pmt_es_stream_type_changes;
> > +
> >      int skip_changes;
> >      int skip_clear;
> >      int skip_unknown_pmt;
> > @@ -199,6 +201,8 @@ static const AVOption options[] = {
> >      MPEGTS_OPTIONS,
> >      {"fix_teletext_pts", "try to fix pts values of dvb teletext
> streams", offsetof(MpegTSContext, fix_teletext_pts), AV_OPT_TYPE_BOOL,
> >       {.i64 = 1}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
> > +    {"reprobe_stream_if_pmt_es_stream_type_changes", "allow PMT updates
> to change codec_type and codec_id at runtime",
> > +     offsetof(MpegTSContext,
> reprobe_stream_if_pmt_es_stream_type_changes), AV_OPT_TYPE_BOOL, {.i64 =
> 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
> >      {"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,
> > @@ -2510,7 +2514,9 @@ static void pmt_cb(MpegTSFilter *filter, const
> uint8_t *section, int section_len
> >          if (!st)
> >              goto out;
> >
> > -        if (pes && pes->stream_type != stream_type)
> > +        if (pes && (!pes->stream_type ||
> > +                    (pes->stream_type != stream_type &&
> > +                     ts->reprobe_stream_if_pmt_es_stream_type_changes)))
> >              mpegts_set_stream_info(st, pes, stream_type, prog_reg_desc);
> >
> >          add_pid_to_program(prg, pid);
> > diff --git a/tests/fate/demux.mak b/tests/fate/demux.mak
> > index ead5ad4b10..6e5e2eb81a 100644
> > --- a/tests/fate/demux.mak
> > +++ b/tests/fate/demux.mak
> > @@ -158,7 +158,7 @@ FATE_SAMPLES_DEMUX-$(CONFIG_XWMA_DEMUXER) +=
> fate-xwma-demux
> >  fate-xwma-demux: CMD = crc -i $(TARGET_SAMPLES)/xwma/ergon.xwma -c:a
> copy
> >
> >  FATE_FFPROBE_DEMUX-$(CONFIG_MPEGTS_DEMUXER) += fate-ts-demux
> > -fate-ts-demux: CMD = ffprobe_demux
> $(TARGET_SAMPLES)/ac3/mp3ac325-4864-small.ts
> > +fate-ts-demux: CMD = ffprobe_demux
> $(TARGET_SAMPLES)/ac3/mp3ac325-4864-small.ts
> -reprobe_stream_if_pmt_es_stream_type_changes 1
> >
> >  FATE_FFPROBE_DEMUX-$(CONFIG_MPEGTS_DEMUXER) += fate-ts-timed-id3-demux
> >  fate-ts-timed-id3-demux: CMD = ffprobe_demux
> $(TARGET_SAMPLES)/mpegts/id3.ts
>
> IMO this should not be mpegts specific, but for all demuxers. Other
> (header-less) formats may have the same issue.
>

Okay, but I only have mpeg-ts samples to test this with,
so I wanted to keep the scope of changes confined to mpegts.

Anyway, how would I go about doing it for all demuxers?
Would that be a new AVFormatContext option, like
`skip_estimate_duration_from_pts`?
I'll send a new patch.

Thank you,
    Pavel
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