Re: several second latency with USB audio

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Понедельник, 11 января 2016, 10:47 +01:00 от Clemens Ladisch <cladisch@xxxxxxxxxxxxxx>:

Sergei Steshenko wrote:
> Воскресенье, 10 января 2016, 22:40 +01:00 от Clemens Ladisch <cladisch@xxxxxxxxxxxxxx>:
>
> Sergei Steshenko wrote:
> >> Пятница, 8 января 2016, 10:14 +01:00 от Clemens Ladisch <cladisch@xxxxxxxxxxxxxx </compose?To=cladisch@xxxxxxxxxxxxxx>>:
> >> Sergei Steshenko wrote:
> >>> Понедельник, 4 января 2016, 18:45 +01:00 от Clemens Ladisch < cladisch@xxxxxxxxxxxxxx </compose?To=cladisch@xxxxxxxxxxxxxx> >:
> >>> What is the buffer length of the device?
> >>> (see /proc/asound/card*/pcm0p/sub0/hw_params)
> >>>
> >>> "buffer_size: 262144", and 262144/48000 is about 5.46 seconds - feels about right.
> >>
> >> The audio device is configured by whatever program actually writes to it,
> >> probably your host. What is it? How is it configured?
> >
> > the program is 'ecasound'.
>
> And how have you configured ecasound? Is it using Jack? If yes, how have
> you configured Jack?
>
> Ecasound does not use Jack, and I used '-b 1024' on command line.
>
> Is there a default buffer length which does not depend on the application ?

No. The application always sets the buffer size.

1 MB (= 256k samples) is the maximum USB buffer size. Apparently, ecasound
does not use your setting for USB devices.

> in 2.6.* kernels there was a module parameter determining latency

That was for a different buffer.


Regards,
Clemens

"Apparently, ecasound does not use your setting for USB devices" - how does it know it's a USB device in the first place ? I.e. does ALSA API provide access to such info ?

Anyway, I strongly doubt your assertion. Ecasound was meant as pretty much real time, with real time capability which it always tries to use (but requires access permissions to really increase real time priority).

Regards,
  Sergei.
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