[vlc-devel] [PATCH 08/17] es_out: use the input_clock as a master source of vlc_clock

Rémi Denis-Courmont remi at remlab.net
Mon Feb 22 11:04:24 UTC 2021

Le perjantaina 19. helmikuuta 2021, 10.38.09 EET Thomas Guillem a écrit :
> Thanks for this review, you raise an important point. Let me enumerate what
> my patch set is changing and what could be discussed.
>  - 1/ We add back the input (PCR) as clock master, disabled by default. This
> feature is likely to be used by advanced users.
>  - 2/ We now use the input clock to calculate the pts_delay for the Output.
> When converting the first PTS, the master ES will use the input clock to
> convert its PTS. Once the master ES is started, (the first
> vlc_clock_Update() is called), it won't use the input clock anymore.
> The pts_delay calculated by this new way is now the same as what we were
> doing in VLC 3.0 (you can easily see it by comparing the starting differed
> logs in pulse audio). When we added the clock, we tried to emulate this
> calculation via vlc_clock_main_SetFirstPcr() and
> vlc_clock_main_SetInputDejitter() but the results are not exactly the same.
> - 3/ If there is no master, the input clock is used as master (like in VLC
> 3.0).
> I think the points 1/ and 2/ are valid. What do you think?

I don't see how that makes any sense, for the simpel reason already outlined 
that, in most cases, there is NO input clock.

You seem to confuse input clock with ES output pacing which meant for flow 
control and buffering, not for clock. If anything, not confusing clock and 
buffer was the main point of the whole clock rework.

Rémi Denis-Courmont

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