[pulseaudio-discuss] Toslink capture looback latency problem

NicoHood pulseaudio-discuss at nicohood.de
Sun Feb 18 09:15:58 UTC 2018

On 02/14/2018 07:45 AM, Georg Chini wrote:
> On 13.02.2018 20:36, NicoHood wrote:
>> On 01/29/2018 07:39 PM, NicoHood wrote:
>>> On 01/29/2018 07:19 PM, Georg Chini wrote:
>>>> On 29.01.2018 18:46, Nico wrote:
>>>>> On 01/29/2018 03:52 PM, NicoHood wrote:
>>>>>> On 01/29/2018 03:29 PM, Georg Chini wrote:
>>>>>>> On 29.01.2018 14:44, NicoHood wrote:
>>>>>>>> On 01/29/2018 01:39 PM, Georg Chini wrote:
>>>>>>>>> On 29.01.2018 12:52, Nico wrote:
>>>>>>>>>> Hi,
>>>>>>>>>> I want to capture the audio stream of my TV with my PCI-E Toslink
>>>>>>>>>> sound
>>>>>>>>>> card and play it back on my usb XLR soundcard. The reason why I
>>>>>>>>>> do that
>>>>>>>>>> is to use my own music boxes rather than the TV speakers. With
>>>>>>>>>> toslink +
>>>>>>>>>> XLR I do not have problems with ground loops etc.
>>> With 48kHz The sound is working properly now. The problem I got ~~now~~
>>> is that there is sound distortion in the recording. -> A reboot fixed
>>> that.
>>> Is there any negative effect when using 48kHz as default sample rate? Is
>>> there a way to configure only the loopback module with this special
>>> sample rate? (Sorry, I have no idea how audio works internally). And if
>>> there is no other way than configuring the default sample rate, how can
>>> is set this as user (without root) if possible?
>>> Thanks a lot so far :)
>> For some reason I got the sound distortion back and it is not fixable
>> via reboot. I cannot tell where this is coming from, its really strange.
>> Any ideas?
> Maybe this is a volume issue. Have you tried removing the files
> in ~/.config/pulse (*-volume.*) and restarting PA?

I found other reasons for the sound distortion:
If pulseaudio is receiving a report input stream (configured via
paprefs) it lags. But that does not seem to be the only reason.
Depending on which window is focussed it laggs more or sometimes less.

So to me it seems to be cause by either CPU, Ethernet (cable), Graphics
card, or pulseaudio itself.

This still looks a bit random to me, as the CPU is not at the maximum.
It must be something else. At least I can play with these parameters now
and try to find the real cause.

If I open pavucontrol and select the first or last tab "playback" or
"configuration" it starts lagging. All other tabs work fine. If I open
the system monitor in parallel, but not in the foreground it still laggs
a but, but way less. Pavucontrol is maximized. I am using gnome3 on
Archlinux. I am testing this with a running vnc/vino session, as the TV
only outputs music when my Gaming console is selected as input, not the
computer I a debugging.

I have no idea why opening a special program or selecting a special tab
causes pulseaudio to lagg abnormally. I must be missing something!?

I did not try to delete the volume files, as it seems to be caused by
something else. I've checked the volume manually though, looking good.


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