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

[Rémi Denis-Courmont]

Le tiistaina 16. maaliskuuta 2021, 23.41.51 EET Alexandre Janniaux a écrit :
> Hi,
> 
> On Tue, Mar 16, 2021 at 11:18:58PM +0200, Rémi Denis-Courmont wrote:
> > Le tiistaina 16. maaliskuuta 2021, 22.45.36 EET Alexandre Janniaux a écrit 
:
> > > > - Sometimes playback never "catches up".
> > > 
> > > What do you mean by «never catches up»?
> > 
> > The same symptoms as Thomas claims to be happening now.
> > 
> > > > - Especially as start/resume, doppler sound effect (resampling) due to
> > > > abnormally quick succession of SetPCR calls.
> > > 
> > > The «doppler sound effect» on 3.0 and the artifacts were
> > > happening because of the way this clock was implemented, ie
> > > it's only about how you resample and filter the result.
> > 
> > No. It's about how the clock was measured. Resampling was working as
> > intended when the master clock and the audio clock drift from one
> > another.
> 
> If you squeeze audio, it will get pitched up, so you need to
> be sure there's silence in that place, or audio that has been
> stretched to match the frequency used. Using the input PCR as
> clock will guarantee that there are audio glitch someday, but
> it's cannot generate high pitch sound. Clock is about time, not
> sound.

I completely disagree here as already explained.

> > > It doesn't mean that using the input PCR is incorrect.
> > 
> > Actually, it does mean exactly that.
> 
> My interpretation is arbitrary too but is at least sustained
> by the clock design document. Can you be more explicit about
> why it means exactly that for you?

I have no problem with the design document. The points are:
1) This patchset is not what the design document says. It is nowhere said to 
add the input to the audio master clock. Also what Denis pointed out.
2) The old actual *implementation* of the "input PCR clock" is well-known 
broken causing the issues I already mentioned. Implementation, not concept.

-- 
レミ・デニ-クールモン
http://www.remlab.net/