[LAU] Audio Interface for live Processing

[James Stone]

On Sun, Jan 27, 2013 at 10:32 PM, Len Ovens <len at ovenwerks.net> wrote:
>
> On Sun, January 27, 2013 12:20 pm, James Stone wrote:
>> On Sun, Jan 27, 2013 at 4:05 PM, Saul Rayson <saul at atonic.com> wrote:
>
>>>>For live work, Guitar effects, soft synths, etc. USB 1.1 at 16bit/48k
>>>> may
>>>>work just fine
>>>
>>> My experience with USB audio is limited, but USB 1 on mac, for live
>>> processing, I have found to have unusable latency.
>>>
>>
>> Latency in 1.1 vs usb 2 shouldn't be significantly different as I
>> understand it. usb 2 just allows higher bandwidth - so more channels
>> or 24bit vs 16bit. Just depends on whether the interface is properly
>> supported in linux.
>
> I have used a USB 1.1 IF on my netbook running at 800Mhz (half speed) and
> was still able to run the IF at -p 64 -n 2 (2.67 ms Latency) without
> xruns. I did have to back the latency off if I ran too many softsynths or
> too many effects, but even double that is not bad. -p 64 with USB 2
> devices seems to be the lowest too. I run into memory problems before CPU
> use problems in general with only 1G memory :)

.. actually on the Scarlett 2i4, I can start jack with -p 16 -n 2..
but it's not really usable on my ageing PC (Athlon 2500XP 1G RAM)..
lots of xruns.. It will run xrun free at 48k with -p32. push it up to
-p64, and it is pretty solidly stable at 96000 sample rate. Note 2.67
is round trip latency - from sound in to sound out. For midi control
of softsynths, it is half that.

With very short sample sizes, linuxsampler complains that the audio
fragment size is too small though! I think linuxsampler (at least the
version shipped with ubuntu) requires a period of 128 to run
correctly..

James