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

From: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
To: ffmpeg-devel@ffmpeg.org
Subject: Re: [FFmpeg-devel] [PATCH] avformat/mpegts: Add -reprobe_stream_if_pmt_es_stream_type_changes option
Date: Sun, 15 Jun 2025 05:24:34 +0200
Message-ID: <AS8P250MB07446210F7B6D43F419298958F71A@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20250614195828.20357-1-pkoshevoy@gmail.com>

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.

- Andreas

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