Re: [LAU] Affordable well-working USB interface with low latency at 48kHz?

Giso Grimm <gg3137@vegri.net> writes:

> Here is data for the Focusrite Scarlett solo for all period sizes P from
> 16 to 240 frames in steps of 16 frames:
>
> P frames ms
> 16 114.847 2.393
> 32 176.847 3.684
> 48 232.847 4.851
> 64 294.847 6.143
> 80 368.847 7.684
> 96 424.847 8.851
> 112 498.847 10.393
> 128 566.847 11.809
> 144 616.847 12.851
> 160 684.847 14.268
> 176 752.847 15.684
> 192 802.847 16.726
> 208 876.847 18.268
> 240 1000.847 20.851
>
> This is almost perfectly 4*P+48, for all P. I can also start it with P =
> 37 (an arbitrary prime number), so it looks that there is no limitation
> on the period size. Also for such odd numbers it remains 4*P+48 (the
> exact delay varies a bit between jack starts, which is normal for USB
> devices).
>
> This is jackd2 - I don't know if jackd1 behaves differently (although
> both would use the underlying ALSA layer).
>
> I started jack with
>
> jackd --sync -P 90 -d alsa -d hw:$CARD -r $RATE -p $PERIODSIZE

--sync is not documented in jackd2's man page. What does it do?

-- 
David Kastrup
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