20 Jan
2017
20 Jan
'17
4:49 p.m.
On Fri, 20 Jan 2017, Ralf Mardorf wrote:
With linux 4.9.0-rt1 it's possible to go down to
32 frames at 48 KHz,
getting lots of inaudible xruns, at 16 frames as well as 64 frames the
interface is completely unusable. At 128 frames it's the same as for a
vanilla kernel with threadirqs, just scrolling with the USB mouse wheel
in roxterm usually does cause issues, very seldom a random xrun could
happen, when switching to another window. At 256 frames it seems to be
absolutely stable, however, it seems to be usable at 128 frames, with
linux-rt as well as a vanilla linux with threadirqs. FWIW using another
USB cable at 128 frames doesn't make a difference. Actually it even
seems to be usable at 32 frames, the xruns were inaudible. I don't know
why it's completely broken at 64 frames. 16 and 64 frames cause long
interrupted audio signals.
16/2 is less than 1ms at 48k... 16/3 at 48k is 1ms, maybe try 16/3, 32/3,
64/3 to see if that works better (at 48k) as they are all multiples of
1ms. It seems to me USB does things in 1ms intervals. (this is all based
on rumours and conversation bits I recall... not hard knowledge on USB)
--
Len Ovens
www.ovenwerks.net