[pulseaudio-discuss] How do different sound cards dynamically use different configurations?

[Sean Greenslade]

On Fri, Jul 15, 2022 at 06:04:49PM +0800, zhaochengyi at uniontech.com wrote:
> Hi guys,
> 
> On a special PC, it is required to start the pulseaudio daemon
> with some special parameters in the file /etc/pulse/daemon.conf,
> as follows:
> 
> -------
> default-sample-rate = 48000
> default-fragments = 2
> default-fragment-size-msec = 20
> -------
> 
> When plugging in a USB headset with a separate sound card to this special
> PC,
> I found that there was a noise in the playback audio. After investigation,
> the sound card of the USB headset needs to use the following default
> parameters.
> 
> -------
> default-sample-rate = 44100
> default-fragments = 4
> default-fragment-size-msec = 25
> -------
> 
> So, how to enable the parameters required by the sound card
> of the USB headset when using it.

Assuming you are using pulseaudio 15.0 or newer, there is a feature to
apply module-alsa-card parameters by udev rule. See:

https://freedesktop.org/wiki/Software/PulseAudio/Notes/15.0/#index8h3

Just craft an appropriate udev rule that matches your USB headset and
include the PULSE_MODARGS variable with rate / fragments / fragment_size
set appropriately. Note that fragment_size is in bytes, see the docs for
more info:

https://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/Modules/#module-alsa-card

--Sean