10 Jan
2014
10 Jan
'14
11:31 a.m.
On Fri, Jan 10, 2014 at 7:48 AM, Clemens Ladisch <clemens(a)ladisch.de> wrote:
Tim Goetze wrote:
Hi Clemens!
Is there anything that happened to snd-usb-audio (or the underlying
usb kernel code) between 3.0.36 and 3.6+ that might explain why it is
no longer possible to get clean audio with a frame/period size of less
than 128/2 using jack on the Scarlett 2i4?
James
[Clemens Ladisch]
In the case of the current version of snd-usb-audio, the queue has the
same length as the buffer, but never more than 18 ms.
In most cases, the ALSA buffer/period parameters
directly reflect
hardware parameters, but in the case of protocols like USB where it is
not possible to transfer data directly out of a ring buffer, there is an
additional packet queue, which adds latency. (The length of that queue
is either constant or proportional to the period size, depending on the
driver.)
Thanks you Clemens for clearing that up. How would one go about
determining the size of this queue between ALSA and USB?