28 Jul
2004
28 Jul
'04
1:06 p.m.
Anyone here know:
1 - How I can measure the latency of a USB-audio device connected to PD via
ALSA?
2 - What the minimum latency of a USB-audio device is with Linux?
Thanks!
Matthew Polashek
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28 Jul
28 Jul
1:18 p.m.
Hi,
Polashek, Matthew wrote:
Anyone here know:
1 - How I can measure the latency of a USB-audio device connected to PD via
ALSA?
There is a patch in "doc/7.stuff/tools/" called latency.pd, which you
can use to measure roundtrip latencies with Pd. It comes with
instructions on use. Pd is *not* callback driven and uses various
buffers, so you will always get double or even triple latency in
Pd compared to something like Ardour.
2 - What the minimum latency of a USB-audio device is
with Linux?
In my experiences with about 20 USB devices "jackstart -p 128" is the
lowest I ever could achieve more or less stable. How low a latency in
msecs that is depends on the samplerate.
Ciao
--
Frank Barknecht
3:07 p.m.
Polashek, Matthew wrote:
2 - What the minimum latency of a USB-audio device is
with Linux?
I guess around 10 ms with default settings.
The snd-usb-audio module has an undocumented parameter "nrpacks"
which is equivalent to the number of milliseconds between USB
interrupts. The default value is 4. You can try setting it to lower
values; the minimum is 1.
HTH
Clemens
3:17 p.m.
Clemens Ladisch wrote:
Polashek, Matthew wrote:
Just out of curiousity, does all this apply to USB-MIDI as well?
Chris
2 - What the minimum latency of a USB-audio device
is with Linux?
I guess around 10 ms with default settings.
The snd-usb-audio module has an undocumented parameter "nrpacks"
which is equivalent to the number of milliseconds between USB
interrupts. The default value is 4. You can try setting it to lower
values; the minimum is 1.
29 Jul
29 Jul
5:21 a.m.
Chris Pickett wrote:
Clemens Ladisch wrote:
No, USB MIDI packets are sent/received as fast as the USB can handle
it (in 1 ms frames). Well, if the computer handles interrupts fast
enough.
Regards,
Clemens
Polashek, Matthew wrote:
Just out of curiousity, does all this apply to USB-MIDI as well? 2 - What the minimum latency of a USB-audio device
is with Linux?
I guess around 10 ms with default settings.
The snd-usb-audio module has an undocumented parameter "nrpacks"
which is equivalent to the number of milliseconds between USB
interrupts.
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7222
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linux-audio-user@lists.linuxaudio.org
4 comments
4 participants
participants (4)
-
Chris Pickett -
Clemens Ladisch -
Frank Barknecht -
Polashek, Matthew