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

Rémi Denis-Courmont remi at remlab.net
Tue Mar 16 17:23:21 UTC 2021

Le tiistaina 16. maaliskuuta 2021, 18.13.23 EET Thomas Guillem a écrit :
> > I don't expect anything good to come out of that.
> It will be used only for inputs with access that can't control the pace
> (udp, live...) and it's already the case in 3.0.

I don't think that's how it works in 3.0, no.

As far as I know, in 3.0, the master clock is always the RTC. If the input is 
paced, then it is adjusted according to a low-pass filter of SetPCR call 
timings. This is wrong and very noisy as those SetPCR calls are used by 
demuxer according to ES buffers, not time/clock.

Indeed, this method has been known to cause issues:
- Sometimes playback never "catches up".
- Especially as start/resume, doppler sound effect (resampling) due to 
abnormally quick succession of SetPCR calls.

In 4.0, the master clock is no longer always the RTC, and the audio output 
timing is handled differently in 4.0 as it was in 3.0.

So it's like comparing apples and oranges.


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