11 Dec
2013
11 Dec
'13
1:35 a.m.
It doesn't have to be; what matters is that's it being scheduled into
a space that fragments the bandwidth the audio device needs.
Even if the audio device only needs 3% of the bandwidth and the mouse
.0001%, the mouse drops that USB frame into low-speed compat mode and
blocks all higher speed devices from using any bandwidth during that
timing period. If the audio device requires a tiny, uninterrupted
piece of scheduling every period, it's just lost any chance of
successful scheduling.
On top of this, the Linux host schedulers are not particularly
effective about avoiding these conflicts.
[sorry for some ambiguity above; I don't remember if 1.0/1.1 drops a
full frame to low speed or just the microframe].
Monty
On Tue, Dec 10, 2013 at 8:28 PM, Bob van der Poel <bob(a)mellowood.ca> wrote:
On Tue, Dec 10, 2013 at 6:04 PM, Gabriel M.
Beddingfield
<gabrbedd(a)gmail.com> wrote:
On 12/10/2013 02:12 PM, Bob van der Poel wrote:
Makes sense. But all that's on the port is a mouse and the telephone.
I don't see either one using much bandwidth. She uses the same port to
read pics from a camera, but that was not plugged. And, I rebooted to
make sure things were cleared out. Guess I've got a greedy mouse :)
--
**** Listen to my FREE CD at http://www.mellowood.ca/music/cedars ****
Bob van der Poel ** Wynndel, British Columbia, CANADA **
EMAIL: bob(a)mellowood.ca
WWW: http://www.mellowood.ca
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Figured it out after a few hours :) We'd only recently plugged her
mouse into the same multiport. If the "telephone" is plugged into a
different port, it works. If the mouse is not plugged into the
multiport, it works.
Yeah, that's one of the hidden pull-your-hair-out gotchas of USB Audio. I
ran into it once where an audio device was on the same hub as a webcam --
and that didn't work well.
The deal is that the audio device reserves a certain amount of bandwidth
over USB. If it can't get -- it won't even try to work. So if some other
device has reserved the bandwidth you need (which they can), then there's no
room left over for yours.
-gabe