| Message ID | 1688408109-14381-5-git-send-email-dheitmueller@ltnglobal.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add passthrough support for SCTE-35 | expand |
| Context | Check | Description |
|---|---|---|
| andriy/configure_x86 | warning | Failed to apply patch |
On Mon, 3 Jul 2023, Devin Heitmueller wrote: > Changes were made between in the last two years to periodically > send PCR-only packets on all PIDs, but for cases where the stream > may send packets very infrequently (like SCTE-35), this results in > extra TR101290 errors because it fails the PCR interval test. > > I am not quite sure what the "right" fix should be for this, but > for now just disable all periodic sending of PCR-only packets on > SCTE-35 streams. Hmm, only one PID per service should generate PCR, and if there is a video stream in the service, then that is preferred for PCR generation. An SCTE stream should only get selected for PCR if there are no video streams in a service. Or are you seeing something else? And it is also strange that not sending PCR for any stream improves the PCR interval test, it should make it worse, because less PCRs are provided, no? Thanks, Marton > > Signed-off-by: Devin Heitmueller <dheitmueller@ltnglobal.com> > --- > libavformat/mpegtsenc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c > index c6cd1fd..ba60582 100644 > --- a/libavformat/mpegtsenc.c > +++ b/libavformat/mpegtsenc.c > @@ -1579,7 +1579,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st, > int st2_index = i < st->index ? i : (i + 1 == s->nb_streams ? st->index : i + 1); > AVStream *st2 = s->streams[st2_index]; > MpegTSWriteStream *ts_st2 = st2->priv_data; > - if (ts_st2->pcr_period) { > + if (ts_st2->pcr_period && st2->codecpar->codec_id != AV_CODEC_ID_SCTE_35) { > if (pcr - ts_st2->last_pcr >= ts_st2->pcr_period) { > ts_st2->last_pcr = FFMAX(pcr - ts_st2->pcr_period, ts_st2->last_pcr + ts_st2->pcr_period); > if (st2 != st) { > -- > 1.8.3.1 > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-request@ffmpeg.org with subject "unsubscribe". >
Hi Marton, On Mon, Jul 3, 2023 at 3:20 PM Marton Balint <cus@passwd.hu> wrote: > Hmm, only one PID per service should generate PCR, and if there is a video > stream in the service, then that is preferred for PCR generation. An SCTE > stream should only get selected for PCR if there are no video streams in a > service. Or are you seeing something else? > > And it is also strange that not sending PCR for any stream improves the > PCR interval test, it should make it worse, because less PCRs are > provided, no? You make valid points. Admittedly this is a patch I wrote a couple of years ago that has been ported to master, and it's entirely possible that the description is incorrect. I definitely made the patch in response to seeing that I was getting recurring PCR packets on the SCTE-35 stream (which is contrary to SCTE-35's typical behavior where you typically only get packets on the PID when there is an actual trigger). Also, you generally don't have PCRs delivered on streams that are composed only of sections (i.e. not containing PES packets), although I haven't looked to see if that's technically illegal. I will back out the patch and better document the behavior I am seeing and update the patch description so it's more clear why it is needed. Regards, Devin
diff --git a/libavformat/mpegtsenc.c b/libavformat/mpegtsenc.c index c6cd1fd..ba60582 100644 --- a/libavformat/mpegtsenc.c +++ b/libavformat/mpegtsenc.c @@ -1579,7 +1579,7 @@ static void mpegts_write_pes(AVFormatContext *s, AVStream *st, int st2_index = i < st->index ? i : (i + 1 == s->nb_streams ? st->index : i + 1); AVStream *st2 = s->streams[st2_index]; MpegTSWriteStream *ts_st2 = st2->priv_data; - if (ts_st2->pcr_period) { + if (ts_st2->pcr_period && st2->codecpar->codec_id != AV_CODEC_ID_SCTE_35) { if (pcr - ts_st2->last_pcr >= ts_st2->pcr_period) { ts_st2->last_pcr = FFMAX(pcr - ts_st2->pcr_period, ts_st2->last_pcr + ts_st2->pcr_period); if (st2 != st) {
Changes were made between in the last two years to periodically send PCR-only packets on all PIDs, but for cases where the stream may send packets very infrequently (like SCTE-35), this results in extra TR101290 errors because it fails the PCR interval test. I am not quite sure what the "right" fix should be for this, but for now just disable all periodic sending of PCR-only packets on SCTE-35 streams. Signed-off-by: Devin Heitmueller <dheitmueller@ltnglobal.com> --- libavformat/mpegtsenc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)