[pulseaudio-discuss] How does automatic output resampling in Pulseaudio work?

Tanu Kaskinen tanuk at iki.fi
Mon Feb 18 13:39:09 PST 2008

On Mon, Feb 18, 2008 at 10:37:09PM +0200, Tanu Kaskinen wrote:
> If I understood you correctly, then the answer is that there
> is no "final hardware matching stage". In your example the
> sound card reports that it uses sampling rate of 48000 Hz,
> and pulseaudio trusts that it's correct information. If it's
> not, then the sound is played slightly too fast or too
> slowly. The small deviation is taken into account only when
> there are multiple clocks, for example two sound cards, and
> even then the correction is not based on actual time, but
> just the observed difference in the clocks.
> So resampling is always done only once (afaik).

I take back what I said about multiple clocks. Firstly, in
that case resampling seems to happen twice, and secondly I'm
not so sure what module-combine keeps as the reference
clock. All streams created by it have a fluctuating sample

The normal one-card operation uses only one resampling
phase, though, and the target rate is whatever the card is
configured to use.

Tanu Kaskinen

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