[linux-audio-dev] M-Audio and jack

[Ignacio Ramírez]

Hi all,
I have a Compaq Presario notebook with an AMD64 3000+ and I am trying to use
an M-Audio MobilePre for home studio and realtime effects.
This machine comes with an nforce3 chipset, including an intel8x0 sound
card.

I have a 2.6.12rc4-mm2 kernel with the realtime module loaded.
I also have tmpfs mounted on /tmp

I have two problems with jack:

With the intel8x0 I can get jackd to run smoothly, but sometimes (when
launching some program for example) I get many xruns even with realtime
scheduling. Here's how I start it:

jackd -R -d alsa -d "hw:0" -p128 -n2 -S -r48000

but still, it works quite decently. I tried this with realtime effects
(ecamegapedal)
and no problem.

However, if I try the same configuration with the the M-Audio card
(which is mapped to card 2, full duplex is implicit)

jackd -R -d alsa -d "hw:2" -p128 -n2 -S -r48000

I get a lot of xruns. Then, if I try something like

jackd -R -d alsa -d "hw:2" -p512 -n2 -S -r48000

I get NO xruns either, but the sound is completely "chopped". This only
stops happening with a period size of 2048!! Of course, at this point I can
only use it as a recording/playback device but I have to forget about
realtime
effects!

I know that the USB 2.0 bandwidth is more than enough to work in full
duplex mode with two channels at 48000hz (even USB 1.1 bandwidth is
enough for this purposes). Can it be something about the snd-usb-audio
driver being too slow?

Any suggestions?

Thanks,

Ignacio Ramirez.-