[pulseaudio-discuss] Toslink capture looback latency problem

Georg Chini georg at chini.tk
Mon Jan 29 14:29:56 UTC 2018

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.
>>> I am using the pulseaudio loopback module with its default
>>> configuration. The problem is, that the delay between picture and sound
>>> is about one second off, and the longer I wait, the more delay it gets
>>> (30 seconds and more). It is no usable like this.
>>> I tried to play with the latencies of source, sink and the tv delay
>>> itself without sucess. I also tried streaming with pacat directly as
>>> described here:
>>> https://thelinuxexperiment.com/fix-pulseaudio-loopback-delay/
>>> I also tried to change different parameters of the loopback module or
>>> the sources/sinks, but that did not help. I never changed any global
>>> pulseaudio config to avoid larger configuration issues. The CPU usage of
>>> pulseaudio is at 3% with the loopback module
>>> Can anyone help me to get rid of this lag?
>> Hi Nico,
>> which version of PA are you using? Can you provide logs?
>> Regards
>>               Georg
> Hi Georg,
> oh sure I completely forgot:
> pulseaudio 11.1-1 (Arch Linux)
> uname -a: Linux zebes 4.14.15-1-ARCH #1 SMP PREEMPT Tue Jan 23 21:49:25
> UTC 2018 x86_64 GNU/Linux
> Here is a logfile:
> LANG=C pulseaudio -vvvv --log-time=1 > ~/pulseverbose.log 2>&1
> https://gist.github.com/NicoHood/85976f426e1621e599253ee1a95230dd
> Regards
> Nico

This is weird. It looks like the source sample rate is so much higher
than the sink rate that module-loopback can't adapt. No idea why
this happens. Does it work with another input?

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