[Jack-Devel] What about the number of buffers?

[Ralf Mardorf]

On Thu, 8 Aug 2019 12:49:42 +0900, crocket wrote:
>On Thu, Aug 8, 2019 at 3:31 AM Ralf Mardorf wrote:
>> On Wed, 2019-08-07 at 16:59 +0200, Holger Marzen wrote:  
>> > What is the difference between
>> >   jackd -n2 -p192
>> > and
>> >   jackd -n3 -p128  
>>
>> Anything other than -n2 is for esoteric reasons:
>>
>> https://wiki.linuxaudio.org/wiki/list_of_jack_frame_period_settings_ideal_for_usb_interface
>>
>> There might be some truth behind the theory, but in practise
>> something like 128 or 256 frames, 2 periods/buffer at 48 KHz works
>> without issues.
>Do recent usb soundcards need "-n 3"?

Seemingly USB's packet size is the reason for the 1 ms cadence. I don't
have a clue if this is the case for USB 3. The Focusrite 3rd generation
Scarlett series are USB 3 audio interfaces, but I don't know if they
still work with Linux. At https://www.gearslutz.com/ forums you could
ask and probably would get a reply from Focusrite.

I once tested a Presonus Audiobox 1818VSL and I own a Focusrite
Scarlett 18i20 2nd generation, but I never tested 3 periods/buffer,
since 2 periods/buffer just do the job, even if the latency isn't a
multiple of 1ms. With USB I even get way lower latency than is
possible with a TerraTec PCI and a RME PCIe card on at least two used
Linux machines. On the newer machine I even don't unbind USB ports,
respl. I don't care about IRQs at all.

YMMV!

-- 
https://soundcloud.com/der-lichtecho-plan