Re: [Jack-Devel] jackd2 does not start with Terratec 6fire USB
On Sat, 29 Oct 2011 10:07:39 -0400
Paul Davis <[hidden]> wrote:
> On Sat, Oct 29, 2011 at 9:50 AM, richard lucassen
> <[hidden]> wrote:
>
> > period_size: 600
> > buffer_size: 22050
>
> this is pretty seriously braindead. that means that the overall buffer
> in use is 36.75 periods long. every 37th period will be split across
> the beginning and end of the buffer. ALSA can handle this kind of
> nonsense, and thus JACK can too, except that its not going to ever ask
> for an equivalent h/w configuration because it will never ask for a
> buffer size that is anything other than the -n value multiplied by the
> -p value, and both of them are integral.
>
> its also fairly braindead in another way too: huge i/o latency (half a
> second), yet with no actual decrease in CPU load since the device
> keeps waking up the CPU every 600 samples. all the downsides of large
> latency with none of the benefits ...
>
> and in another way: 600 samples isn't a divisor of the USB transfer
> frame size, which will cause additional issues with load etc.
>
> you should definitely find somebody else who has used this with JACK
> and/or talk to the author of the driver of this card (except that i
> would have guessed that it was a generic USB class 1 audio driver ...
> so ... ?)
So, I will forward your answer to the author of the driver. It's all
here:
http://sourceforge.net/projects/sixfireusb/
But OTOH: cpu load, that's another story, but could this issue be the
cause of jackd not starting?
R.
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