[FFmpeg-devel] libavformat: add multiple PCR streams in MPEGTS muxer
Andrey Turkin
andrey.turkin at gmail.com
Mon Oct 29 15:20:02 EET 2018
This looks like a (strange) hack to me.
First, you cannot just throw some pids out - that will make a non-standard
compliant stream. PMT will signal missing streams; PCR pid will be missing
also. So let's assume that your tool can also rewrite PMT.
Secondly, there is supposed to be one and only one PCR stream per program;
there is no way to signal multiple PCRs. So let's assume you have some
out-of-band list of PCRs for this particular case (or maybe you can just
assume there are PCR marks in each stream so you can configure your remuxer
accordingly).
Thirdly and most importantly, I might be wrong here but it looks like your
patch just "spreads" same PCRs which would go into single stream over all
program's streams, i.e. overall PCR count doesn't change. Which means that
remuxed stream might have arbitrarily large inter-PCR gaps which is pretty
bad (assuming you care about PCRs at all, which presumably you do).
Also - do you really have multiple audio streams in single program, which
are supposed to be remuxed as separate radio channels? Or same for multiple
video streams? Is this for ABR purposes? Can you describe your use case in
some more details?
пн, 29 окт. 2018 г. в 4:20, <fjdh7h+2jnbu7gpkuczk at guerrillamail.com>:
> From 44c9f3d96c5969349bd2dc4d63e9a8b8e6b5a0e2 Mon Sep 17 00:00:00 2001
> From: M. Sanders <hidden at gmail.com>
> Date: Sat, 27 Oct 2018 21:39:44 +0200
> Subject: [PATCH] libavformat: add multiple PCR streams in MPEGTS muxer
>
> ---
> This simple patch adds two new options to the MPEG-TS muxer.
> You can use them to mark PCRs in additional VIDEO and/or AUDIO streams.
> It's useful when you will remux the output with pid filtering tools.
> For example, if you put PCR in all audio streams, then you can filter
> each audio stream to create a radio service.
> PCR marks do not disturb outgoing stream, but it is not recommended
> to do so as a regular rule.
>
> doc/muxers.texi | 6 ++++++
> libavformat/mpegtsenc.c | 19 +++++++++++++++++--
> 2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/doc/muxers.texi b/doc/muxers.texi
> index f18543e83d..328707d0ed 100644
> --- a/doc/muxers.texi
> +++ b/doc/muxers.texi
> @@ -1528,6 +1528,12 @@ is @code{-1}, which results in shifting timestamps
> so that they start from 0.
> @item omit_video_pes_length @var{boolean}
> Omit the PES packet length for video packets. Default is @code{1} (true).
>
> + at item pcr_all_video @var{boolean}
> +Include PCR values in all video streams. Default is @code{0} (false).
> +
> + at item pcr_all_audio @var{boolean}
> +Include PCR values in all audio streams. Default is @code{0} (false).
> +
> @item pcr_period @var{integer}
> Override the default PCR retransmission time in milliseconds. Ignored if
> variable muxrate is selected. Default is @code{20}.
> diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c
> index 3339e26d50..caef817a3d 100644
> --- a/libavformat/mpegtsenc.c
> +++ b/libavformat/mpegtsenc.c
> @@ -113,6 +113,8 @@ typedef struct MpegTSWrite {
> double sdt_period;
> int64_t last_pat_ts;
> int64_t last_sdt_ts;
> + int pcr_all_video;
> + int pcr_all_audio;
>
> int omit_video_pes_length;
> } MpegTSWrite;
> @@ -1178,11 +1180,18 @@ static void mpegts_write_pes(AVFormatContext *s,
> AVStream *st,
> int64_t pcr = -1; /* avoid warning */
> int64_t delay = av_rescale(s->max_delay, 90000, AV_TIME_BASE);
> int force_pat = st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && key
> && !ts_st->prev_payload_key;
> + int force_pcr = 0;
>
> av_assert0(ts_st->payload != buf || st->codecpar->codec_type !=
> AVMEDIA_TYPE_VIDEO);
> if (ts->flags & MPEGTS_FLAG_PAT_PMT_AT_FRAMES &&
> st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
> force_pat = 1;
> }
> + if (ts->pcr_all_video && st->codecpar->codec_type ==
> AVMEDIA_TYPE_VIDEO) {
> + force_pcr = 1;
> + }
> + if (ts->pcr_all_audio && st->codecpar->codec_type ==
> AVMEDIA_TYPE_AUDIO) {
> + force_pcr = 1;
> + }
>
> is_start = 1;
> while (payload_size > 0) {
> @@ -1190,7 +1199,7 @@ static void mpegts_write_pes(AVFormatContext *s,
> AVStream *st,
> force_pat = 0;
>
> write_pcr = 0;
> - if (ts_st->pid == ts_st->service->pcr_pid) {
> + if (ts_st->pid == ts_st->service->pcr_pid || force_pcr) {
> if (ts->mux_rate > 1 || is_start) // VBR pcr period is based
> on frames
> ts_st->service->pcr_packet_count++;
> if (ts_st->service->pcr_packet_count >=
> @@ -1228,7 +1237,7 @@ static void mpegts_write_pes(AVFormatContext *s,
> AVStream *st,
> }
> if (key && is_start && pts != AV_NOPTS_VALUE) {
> // set Random Access for key frames
> - if (ts_st->pid == ts_st->service->pcr_pid)
> + if (ts_st->pid == ts_st->service->pcr_pid || force_pcr)
> write_pcr = 1;
> set_af_flag(buf, 0x40);
> q = get_ts_payload_start(buf);
> @@ -1951,6 +1960,12 @@ static const AVOption options[] = {
> { "omit_video_pes_length", "Omit the PES packet length for video
> packets",
> offsetof(MpegTSWrite, omit_video_pes_length), AV_OPT_TYPE_BOOL,
> { .i64 = 1 }, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
> + { "pcr_all_video", "Include PCR values in all video streams",
> + offsetof(MpegTSWrite, pcr_all_video), AV_OPT_TYPE_BOOL,
> + { .i64 = 0 }, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
> + { "pcr_all_audio", "Include PCR values in all audio streams",
> + offsetof(MpegTSWrite, pcr_all_audio), AV_OPT_TYPE_BOOL,
> + { .i64 = 0 }, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
> { "pcr_period", "PCR retransmission time in milliseconds",
> offsetof(MpegTSWrite, pcr_period), AV_OPT_TYPE_INT,
> { .i64 = PCR_RETRANS_TIME }, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM
> },
> --
> 2.11.0
>
>
>
>
>
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