[pulseaudio-discuss] Problem with USB sound card - clicks and pops on re-open

David Henningsson david.henningsson at canonical.com
Mon May 13 23:50:57 PDT 2013

On 05/13/2013 11:19 PM, Christian Iversen wrote:
> On 2013-05-13 05:41, Arun Raghavan wrote:
>> On Sun, 2013-05-12 at 17:18 +0200, Christian Iversen wrote:
>> [...]
>>> Is there any way to have pulseaudio keep the device open at all times?
>>> Or some other way to debug this?
>> Disable the loading of module-suspend-on-idle in /etc/pulse/default.pa.
>> I'm assuming you don't care about the resulting power consumption. :)
> Ah, there is was! :)
> Well, that's great. Thanks!
> I don't think the Scarlett 2i2 really supports any meaningful power save
> mode anyway. It's quite a low-power soundcard to begin with (powered
> entirely by the USB bus).

Not so low-power IMO, it takes about 2-3W of my battery when connected 
(only tested with phantom power on). I think it does that regardless of 
stream running or not, but have not really checked. (The direct monitor 
requires headphone amp and mic amps on anyway.)

> Anyway, even with the official driver for windows, this card has
> terrible clicks and pops when starting up from suspend (or power off).

Ok, good to know.

> Does module-suspend-on-idle have a blacklist? It should! And this card
> should be on it.

There are other reasons for wanting to release the sound card when not 
actively using it - it makes compatibility with other apps easier, i e, 
everything that wants to use ALSA directly (except jack2 which has 
device reservation).

> What does pa use for identifying backends? I mean, if I wanted to
> blacklist certain modules for a specific PCI or USB id, is that
> something that is reasonably easy to do?

Not currently, but it sounds very useful if we had a smart way of 
accomplishing this.

David Henningsson, Canonical Ltd.

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