[FFmpeg-devel] [PATCH] avformat/mpegts: add merge_pmt_versions option
Michael Niedermayer
michael at niedermayer.cc
Tue May 15 15:12:02 EEST 2018
On Mon, May 14, 2018 at 03:54:01PM -0700, Aman Gupta wrote:
> From: Aman Gupta <aman at tmm1.net>
>
> This new optional flag makes it easier to deal with mpegts
> samples where the PMT is updated and elementary streams move
> to different PIDs in the middle of playback.
>
> Previously, new AVStreams were created per PID, and it was up
> to the user to figure out which streams had migrated to a new PID
> (by iterating over the list of AVProgram and making guesses), and
> switch seamlessly to the new AVStream during playback.
>
> Transcoding or remuxing these streams with ffmpeg on the CLI was
> also quite painful, and the user would need to extract each set of
> PIDs into a separate file and then stitch them back together.
>
> With this new option, the mpegts demuxer will automatically detect
> PMT changes and feed data from the new PID to the original AVStream
> that was created for the orignal PID. For mpegts samples with
> stream_identifier_descriptor available, the unique ID is used to merge
> PIDs together. If the stream id is not available, the demuxer attempts
> to map PIDs based on their order and relation to the PCR pid.
>
> With this change, I am able to playback and transcode/remux these
> two samples which previously caused issues:
>
> https://tmm1.s3.amazonaws.com/pmt-version-change.ts
> https://kuroko.fushizen.eu/videos/pid_switch_sample.ts
>
> I also have another longer sample which contains multiple PMT
> changes, some of which change the ES pids and others which do not:
>
> https://tmm1.s3.amazonaws.com/multiple-pmt-change.ts
>
> Demuxing this sample with the new option shows several new log
> messages as the PMT changes are handled:
>
> [mpegts @ 0x7ffe18801200] detected PMT change (version=3/4, pcr_pid=0xf98/0xf9b)
> [mpegts @ 0x7ffe18801200] re-using existing video stream 0 (pid=0xf98) for new pid=0xf9b
> [mpegts @ 0x7ffe18801200] re-using existing audio stream 1 (pid=0xf99) for new pid=0xf9c
> [mpegts @ 0x7ffe18801200] re-using existing audio stream 2 (pid=0xf9a) for new pid=0xf9d
> [mpegts @ 0x7ffe18801200] detected PMT change (version=4/5, pcr_pid=0xf9b/0xfa9)
> [mpegts @ 0x7ffe18801200] re-using existing video stream 0 (pid=0xf98) for new pid=0xfa9
> [mpegts @ 0x7ffe18801200] re-using existing audio stream 1 (pid=0xf99) for new pid=0xfaa
> [mpegts @ 0x7ffe18801200] re-using existing audio stream 2 (pid=0xf9a) for new pid=0xfab
This sounds like an interresting feature
this should also get a fate test
>
> Signed-off-by: Aman Gupta <aman at tmm1.net>
> ---
> doc/demuxers.texi | 4 ++
> libavformat/mpegts.c | 105 +++++++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 105 insertions(+), 4 deletions(-)
>
> diff --git a/doc/demuxers.texi b/doc/demuxers.texi
> index e7c2abce57..2f7d7e0f3a 100644
> --- a/doc/demuxers.texi
> +++ b/doc/demuxers.texi
> @@ -552,6 +552,10 @@ Show the detected raw packet size, cannot be set by the user.
> Scan and combine all PMTs. The value is an integer with value from -1
> to 1 (-1 means automatic setting, 1 means enabled, 0 means
> disabled). Default value is -1.
> +
> + at item merge_pmt_versions
> +Re-use existing streams when a PMT's version is updated and elementary
> +streams move to different PIDs. Default value is 0.
> @end table
>
> @section mpjpeg
> diff --git a/libavformat/mpegts.c b/libavformat/mpegts.c
> index 27b1c30a44..c42e564a7e 100644
> --- a/libavformat/mpegts.c
> +++ b/libavformat/mpegts.c
> @@ -84,6 +84,8 @@ typedef struct MpegTSSectionFilter {
> unsigned int end_of_section_reached : 1;
> SectionCallback *section_cb;
> void *opaque;
> + int orig_pcr_pid; /* pmt specific */
> + int last_pcr_pid;
> } MpegTSSectionFilter;
>
> struct MpegTSFilter {
> @@ -147,6 +149,7 @@ struct MpegTSContext {
> int scan_all_pmts;
>
> int resync_size;
> + int merge_pmt_versions;
>
> /******************************************/
> /* private mpegts data */
> @@ -172,6 +175,8 @@ static const AVOption options[] = {
> {.i64 = 0}, 0, 0, AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_EXPORT | AV_OPT_FLAG_READONLY },
> {"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 },
> + {"merge_pmt_versions", "re-use streams when PMT's version/pids change", offsetof(MpegTSContext, merge_pmt_versions), AV_OPT_TYPE_BOOL,
> + {.i64 = 0}, 0, 1, AV_OPT_FLAG_DECODING_PARAM },
> {"skip_changes", "skip changing / adding streams / programs", offsetof(MpegTSContext, skip_changes), AV_OPT_TYPE_BOOL,
> {.i64 = 0}, 0, 1, 0 },
> {"skip_clear", "skip clearing programs", offsetof(MpegTSContext, skip_clear), AV_OPT_TYPE_BOOL,
> @@ -1073,7 +1078,8 @@ static int mpegts_push_data(MpegTSFilter *filter,
> if (ts->skip_changes)
> goto skip;
>
> - pes->st = avformat_new_stream(ts->stream, NULL);
> + if (!pes->st)
> + pes->st = avformat_new_stream(ts->stream, NULL);
> if (!pes->st)
> return AVERROR(ENOMEM);
> pes->st->id = pes->pid;
> @@ -1982,6 +1988,68 @@ int ff_parse_mpeg2_descriptor(AVFormatContext *fc, AVStream *st, int stream_type
> *pp = desc_end;
> return 0;
> }
> +static AVStream *find_matching_stream(MpegTSContext *ts, int pid,
> + int stream_id,
> + int pcr_pid, int orig_pcr_pid)
> +{
> + AVFormatContext *s = ts->stream;
> + int i, orig_pid = orig_pcr_pid + (pid - pcr_pid);
> + AVStream *found = NULL;
> +
> + for (i = 0; i < s->nb_streams; i++) {
> + AVStream *st = s->streams[i];
> + if (stream_id != -1) {
> + if (st->stream_identifier == stream_id+1) {
> + found = st;
> + break;
> + }
> + } else if (pcr_pid != orig_pcr_pid && st->id == orig_pid) {
> + found = st;
> + break;
> + }
> + }
> +
> + if (found) {
> + av_log(ts->stream, AV_LOG_DEBUG, "re-using existing %s stream %d (pid=0x%x) for new pid=0x%x\n",
> + av_get_media_type_string(found->codecpar->codec_type), i, found->id, pid);
> + }
> +
> + return found;
> +}
> +
> +static int parse_stream_identifier_desc(uint8_t *p, uint8_t *p_end)
> +{
> + const uint8_t **pp = &p;
libavformat/mpegts.c:2022:26: warning: initialization from incompatible pointer type [enabled by default]
> + const uint8_t *desc_list_end;
> + const uint8_t *desc_end;
> + int desc_list_len;
> + int desc_len, desc_tag;
> +
> + desc_list_len = get16(&p, p_end);
type mismatch:
libavformat/mpegts.c:2028:5: warning: passing argument 1 of ‘get16’ from incompatible pointer type [enabled by default]
[...]
--
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
Opposition brings concord. Out of discord comes the fairest harmony.
-- Heraclitus
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