Re: [FFmpeg-devel] [PATCH v2 4/5] mpegtsenc: Don't periodically announce PCR on SCTE-35 streams

[Devin Heitmueller <devin.heitmueller@ltnglobal.com>]

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

-- 
Devin Heitmueller, Senior Software Engineer
LTN Global Communications
o: +1 (301) 363-1001
w: https://ltnglobal.com  e: devin.heitmueller@ltnglobal.com
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