[PD-ot] USB audio Linux success at last!

ailo ailo.at at gmail.com
Sat Jan 29 02:14:07 CET 2011


Normally I would recommend firewire before usb because of the support
issue, but for firewire you'll need a good combination of hardware to
support it.
-The right firewire chip on your computer (not all chips work well)
-no troubling irq sharing issues (can be mended using a -rt kernel and
rtirq script)
-On top of that it seems like some apps, like Network-manager can affect
firewire performance, making it periodically cause xruns on jackd.

At least you get full support on a lot of devices.
And if you do have a good computer to go with it, you get multichannel
support. Even daisy-chaining works if you need more than 8 channels (new
firewire-stack has had an issue not supporting daisy-chaining, but this
aught to be, or has already been corrected).

Playing 16 bit wave files using 24 bit card setting isn't as audible as
playing a 44.1 kHz file with the wrong samplerate. Just an example.
Don't know how these things work on alsa when it comes to 24 bit
setting, and if it truly sets that.
I suppose if you run jackd and it says 24 bit operation then that aught
to mean 24 bit operation.
I know there is a limitation on how much info you can pass using usb 1.1
class compliancy. So that restricts number of channels, bits and
samplerate. How exactly that works, I have no idea.

n 01/29/2011 01:44 AM, Ed Kelly wrote:
> 
> 
>> But do any of you guys get 24 bits and at least 48kHz samplerate? Isn't
>> there some limitations from only having standard usb class compliancy?
>> (didn't check if any of those devices have specific drivers)
> 
> Hmmm, good question. Jack is telling me I have 24 bits capture and playback at 
> 44.1KHz. Haven't tried it at 48 yet, but I'll do some tests once this gig on 
> monday is over.
> 
> I'm not using any specific driver for the Lexicon - Jack is using alsa so 
> snd-usb-audio is the driver I think. The main thing I think is that it seems 
> much more stable than when I was using an edirol FA101 with freebob. That's 
> probably also because I'm using Pure Dyne - Ubuntu 9.10 optimized for audio with 
> the realtime kernel. I won't use anything else now.
> 
> I made the mistake of buying a comp without firewire, but this seems to have 
> been a good mistake now!
> 
> Best,
> Ed

-- 
ailo



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