[PlanetCCRMA] M-Audio Audiophile USB

[Fernando Lopez-Lezcano]

On Sun, 2005-10-02 at 21:23 -0400, Michael Peters wrote:
> 
> Fernando Lopez-Lezcano wrote:
> > On Sat, 2005-10-01 at 15:25 -0400, Michael Peters wrote:
> > 
> >>Rui Nuno Capela wrote:
> >>
> >>>Michael Peters wrote:
> >>>
> >>>>But that still leaves me with the problem of having it appear in the
> >>>>connection window, audio tab under Qjackctl. The midi appears just fine.
> >>>>Any pointers?
> >>>>
> >>>
> >>>Let me clarify something I believe you're missing:
> >>>
> >>>If you're seeing at least one "alsa_pcm" entry under the Audio
> >>>connections tab, than that's a sign that things are working properly, as
> >>>expected. Those are the official names for the client ports that
> >>>represent your soundcard interface, as thru the designated ALSA JACK
> >>>backend. You must have jackd started alright, before you see anything of
> >>>this.
> >>
> >>I do see one alsa_pcm (with capture1, capture2, playback1, playback2)
> >>but I see that one without the usb m-audio audiophile connected. I know
> >>that one works as I played with recording from the on-board sound card
> >>(intel8x0) when I was just getting started.
> >>
> >>Since the USB card doesn't come with a mixer how do I select the
> >>inputs/outputs of it rather than the onboard sound card? I assumed they
> >>would show up in the connect window in qjackctl and I could pick from there.
> > 
> > 
> > Jack can only use one card at a time and yours is not the first one
> > which is the default (see what you have in 'cat /proc/asound/cards',
> > they are there with a zero based index). 
> > 
> > You can choose which card in the "Setup" dialog of qjackctl, yours
> > should be, I think, "hw:2". USB soundcards are tricky to set up to work
> > well with Jack... try with 3 periods or more and sampling rate of
> > 48000. 
> 
> That's the piece of info I was missing, thanks. But "hw" doesn't work
> and after poking around on the alsa mailing list archives I found that
> since the USB Audiophile is big endian I have to use "plughw". I can now
> playback from ardour through jack. I haven't tested recording yet, but
> that's for another day.
> 
> Thanks for the help.
> 
> And if you don't mind another dumb question... what's an "xrun".  During
> the playback with new USB device I get about 1-2 a minute. I know
> everyone tries to minimize them but I just wanted to know what they were
> and what is the general strategy to take to try and reduce them.

Generically an "xrun" is when an application sending or receiving
samples to/from a souncard is not enough and either the soundcard runs
out of samples when playing back or overflows the input buffer when
recording. For playback that translates into a "gap" in the output, for
recording the recording app will miss some samples. 

What to do to try to get rid of them depends on the conditions that are
triggering them. Usually making buffers larger helps (but degrades the
realtime response of the system). 

-- Fernando