Re: [linux-audio-user] linux audio interface

On Fri, 05 May 2006 00:51:49 +0000
Cesare Marilungo <cesare@email-addr-hidden> wrote:

> > 6. MIDI is necessary and also lowest latency possible. (which I don't know
> > what it is on linux)

> I'm really happy with my Edirol UA-25.
>
> http://www.roland.com/products/en/_support/dld.cfm?ln=en&dsp=0&iCncd=526
>
> Latency could be set as low as 5.8ms (2.9ms in +2.9ms out) if the CPU
> load of the session your're working on is not too heavy.

Just as a sidenote: On a -rt system, which is properly setup (irq and
app priorities) and a delta 44/66/1010 you can use periodsizes down to 8
frames. 8 frames at a samplerate of 48000 corresponds to a (roundtrip)
latency of

2 * (8/48000) = 0.0003333. sec = 0.3333... ms

While context switching overhead gets really huge it is in principle
possible to get ridicously low latency (you really don't want to use a
periodsize of 8 frames though. Even jack idle load is around 20-30% with
that setting -> ugh).

Operation with 32 or 64 frames per period is possible without problems
at all.

I don't think this is possible with USB hardware, and i have no idea
whether it's possible with firewire hardware.

The delta card i use is a PCI card and i suppose in principle the same
should be possible with a pcmcia card (which is afaik just a pci bus in
disguise).

Have fun,
Flo

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