[vlc-devel] [PATCH v3 2/6] clock: add vlc_clock_main_SetInputDrift

Thomas Guillem thomas at gllm.fr
Mon Mar 22 11:19:21 UTC 2021

Hello Denis,
Thanks for the review,

On Mon, Mar 22, 2021, at 12:00, Denis Charmet wrote:
> On 2021-03-16 09:11, Thomas Guillem wrote:
> > I agree this may not be the perfect solution, but it is a simple one
> > that will avoid many regressions with livestreams.
> > 
> > To sum-up, this patch set switch back to the monotonic clock (so no
> > master audio) if the access can't control the pace. In that case, the
> > legacy input clock will send averaged drift update to the output
> > clock. This drift won't be used by the master clock (since it's
> > disabled at this point), but by all ES slaves (video, that will be
> > displayed faster/slower, audio, that will be resampled).
> > 
> > Right now, I don't see any other solution. Even if there is a better
> > solution, how long will it take to implement? Should we postpone it to
> > VLC 5.0? Therefore, I suggest that we merge this patch set for VLC
> > 4.0.
> > 
> With this you just add back the "wobbly" effects because it's based on 
> PCR which is unreliable on 99% of the streams handled by VLC.
> What's wrong with just forcing PCR master instead of audio master for 
> such streams without touching the main clock?

This is a good idea.

This is what my first patch set was doing, but I went to far at some points:
 - It was using input clock by default, even for the first audio master synchronization

It could adapt my first branch to:
 - enable the input clock only if can_control_pace == false.

> Regards,
> -- 
> Denis Charmet - TypX
> Le mauvais esprit est un art de vivre
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