[pulseaudio-discuss] Why are we checking various sample rates?

[Arun Raghavan]

On Sat, 2012-12-01 at 20:57 +0800, Raymond Yau wrote:
> 
> 2012-11-30 下午5:01 於 "David Henningsson"
> <david.henningsson at canonical.com> 寫道：
> >
> > Hi,
> >
> > I'm researching a bug where some set of USB speakers stopped
> working, probably in 2.x. The peculiar thing about this sound card is
> that seems to only work at a sample rate of 46875 Hz.
> >
> > So in 2.x, the probe fails with
> > "E: [pulseaudio] alsa-sink.c: Failed to find any supported sample
> rates.", whereas in an earlier version, it would just happily work at
> 46875 Hz instead, as I understand it.
> >
> > So my first question is; why do we check all these rates, when we
> end up just alternating between default-sample-rate (44100 Hz) and
> alternate-sample-rate (48000 Hz) anyway?
> > And second, can we try not to fail if we can't find any supported
> sample rates, so we can fix this regression?
> 
> 
> http://cgit.freedesktop.org/pulseaudio/pulseaudio/commit/src/daemon/daemon-conf.c?id=5bcfd2b630ae56c97348edc93c4c237f71b24283
> 
> Since pulseaudio 2.0 require sound card support sample rate which are
> multiple of 4000 and 11025 

Not entirely true. The ALSA sink will still pick the nearest available
rate. Nevertheless, I'm not really against dropping that check and
amending the rate switching code to be disabled for non-standard default
sample rates.

-- Arun