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

Arun Raghavan arun.raghavan at collabora.co.uk
Sun Dec 2 22:07:14 PST 2012

On Fri, 2012-11-30 at 09:59 +0100, David Henningsson wrote:
> 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?
> For reference, this is the bug (with pulse verbose logs in it):
> https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/1074783

This was added by:

commit e67440e2208fb8182916493b57b75e91013510e7
Author: Arun Raghavan <arun.raghavan at collabora.co.uk>
Date:   Mon Oct 17 22:46:06 2011 +0530

    alsa: Probe sink/source sample rates
    This probes sink and source sample rates and uses this information to
    validate rate changes and check incoming passthrough formats.

So yes, this is a regression. I'm attaching a patch that should fix

-- Arun
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