Thankyou Clemens. And also everyone else who kindly replied to this query. Clemens Ladisch wrote: >> As a followup on this subject (see below) I've come near to a decision >> about the EDIROL UA-20, but still don't know if there's any specific >> issue with JACK for this USB adapter. > > There isn't any specific issue with the UA-20, but with USB devices in > general. > > What all USB devices have in common is that audio data is moved over > the USB bus in frames, and that there are 1000 frames per second. > So, a 48000 Hz stream would move 48 samples per frame, and a 44100 Hz > stream would move 44.1 samples per frame. However, there are no > fractional samples, so the frames would have 44 samples, with one out > of ten frames having 45 samples. > > In theory, one USB frame could be equivalent to one period in ALSA, > but ALSA assumes that period sizes are constant, and Jack further > requires that period sizes are a power of two (which would be true for > most other sound cards). Because of this, ALSA's USB driver sometimes > double-buffers audio data, and emulates arbitrary period sizes on top > of the USB frames. > > The consequence of all this is that you have to use larger period > sizes and/or more than two periods per buffer with Jack, which will > slightly increases your latency. >
OK I see. Now I remember this whole general USB-ALSA-JACK issue from older threads :) but I was much worryied about snd-usb driver support being broken, that is, if any of the proposed USB adapters are not supported by ALSA altogether. I can live with the latency thing, but not with jitter nor silence :) BTW Is firewire/ieee1394 based specifications any better? Can't remember if ALSA has anything to do with it. Cheers. -- rncbc aka Rui Nuno Capela [EMAIL PROTECTED] ------------------------------------------------------- The SF.Net email is sponsored by EclipseCon 2004 Premiere Conference on Open Tools Development and Integration See the breadth of Eclipse activity. February 3-5 in Anaheim, CA. http://www.eclipsecon.org/osdn _______________________________________________ Alsa-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-user
