Re: Digital bit perfect ouptut with ALSA

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Bill Unruh wrote:
> On Mon, 15 Dec 2008, Paulo Moura Guedes wrote:
> > [...]
> > The ASRC, as the name implies, is not syncronized to the clock of
> > the incoming digital signal. Therefore, its performance is independant of the
>
> This makes no sense at all. If the incoming signal is a digital signal, it has
> no clock.

An S/PDIF signal does have a clock (it uses biphase mark coding for
exactly this reason), and there are many DACs that derive their master
clock directly from the input signal.

(It's different in the case of USB where the sample clock is independent
of the bus clock.)

> > quality of that clock. In other words, it doesn't matter if the signal came
> > from a cheap transport with cheap cables, or from a $10,000 signal chain. The
>
> And what the hell do cables have to do with anything? Cables do NOT affect the
> timing.

If the cable's impedance is high enough, the transitions between the
signal levels can be delayed.  This wouldn't matter much except that
due to the biphase mark coding, the jitter is data dependent.

(It's a different question whether the distortions caused by the jitter
are actually audible.)


Best regards,
Clemens

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