[linux-audio-user] Non-xrun noise with ALSA, Jack and an USB soundcard

[Jorma R]

Hi,

I wonder if this is normal...

I get a lot of noise - clicks and pops - when connecting Jack ports. The 
noise appears when I run Jack in duplex mode and with a period size less 
than 2048 frames.

I get no noise if I run Jack with playback only.
If I for example run Hydrogen and connect its ouput ports to alsa_pcm 
playback ports I get noise when in duplex mode but no noise when in 
playback only.

The strange thing is that I get no xruns when the noise appears. I do 
not run out of CPU power either - the CPU usage is down to about 10% 
when running Jack and one client for example.

What I want to do is to record 24-bit audio with my Emagic Emi 6|2m USB 
audio box. I can do this at the moment - the captured audio is clean and 
I can use the hardware monitoring to monitor what is being captured. 
Naturally I would like to get rid of the noise as well to take full 
advantage of what the box should be capable of.

I could simply run Jack with 24-bit capture and with a period size of 
2048 or more but Jack refuses to start with such settings.

Should I just accept the situation as a fact or is there something I 
could do to get rid of the noise when running Jack in duplex mode and 
with 24-bit samples?

The Kernel I am using is a 2.4.25, Alsa is 1.0.3 and Jack is 0.94 all 
from from PlanetCCRMA.

The hardware should be irrelevant - the same problem appears in 3 
different computers I have tried ranging from a Celeron 700 to a P4 2.4 
Ghz.

Ideas, anyone?

Br,

-Jorma

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