On Mon, Mar 07, 2005 at 11:03:50AM -0600, Jack O'Quin wrote: > > Is there an inherent minimum latency for USB soundcards? > > I have no USB sound card. Perhaps someone else can answer that > question. > > There *are* reported latency problems with USB, ALSA and JACK due to > isochronous USB data transfers and JACK's need for a constant power of > two buffer size. IIUC, USB sends a block every 1ms. With some sample > rates this does not result in a constant number of samples in every > block. Progress has been made with certain specific devices (usx2y), > but I believe the general problem still remains. > > These issues seem to become more intrusive at lower latencies. But, I > really don't know what the limits are for your device. I have a Terratec Producer Phase 26 USB soundcard and I have intensively tested 2.4 and 2.6 kernel for stability for hours and lower latency, the best result is with the gentoo-sources 2.4.28 (gentoo kernel are already patches for all audio needs) I run jackd with Frames/Period = 256 Sample Rate = 48000 Periods/Buffer = 3 wich provides a 16ms latency If I try to go lower, I have xruns when I connect/disconnect clients. Regards Philippe
