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

[zhaochengyi at uniontech.com]

Hi Sean,

On 2022/7/20 上午2:59, Sean Greenslade wrote:
> On Mon, Jul 18, 2022 at 02:42:07PM +0800, zhaochengyi at uniontech.com wrote:
>> On 2022/7/17 上午3:18, Sean Greenslade wrote:
>>> 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
>>>> -------
>>
>> After my further investigation, I found that noise is only generated
>> when changing the sink-input volume (pa_context_set_sink_input_volume),
>> but not when changing the sink volume (pa_context_set_sink_volume_by_index).
> 
> Can you describe this noise more specifically? Does it go away with
> larger fragment size / counts? Have you enabled or disabled tsched? Have
> you run with Pulse debug logging enabled and looked for any hints there
> (e.g. underruns)?

I found out I only modified the item default-sample-rate in the file 
'/etc/pulse/daemon.conf', and then it will occur the the noise when 
changed the sink input volume.

   default-sample-rate = 48000
; alternate-sample-rate = 48000

I think the merge_requests 120 can fix this noise issue:
https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/120

Thanks a lot.

Best Regards,
Chengyi