[linux-audio-user] low latency 2.4 help - needed

[Dubphil]

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