[LAU] midi backend not working in qjackctl?

Devin Anderson surfacepatterns at gmail.com
Wed Mar 14 17:00:50 UTC 2012


On Wed, Mar 14, 2012 at 9:04 AM, Paul Davis <paul at linuxaudiosystems.com> wrote:
> On Wed, Mar 14, 2012 at 11:52 AM, Ralf Mardorf
> <ralf.mardorf at alice-dsl.net> wrote:
>
>> Especially in combination with Jack2's -Xalsarawmidi you'll get zero hw
>> MIDI jitter, aka hard real-time.
>
> I don't know if this is the new code that was added recently.
>
> If its the old stuff then it absolutely is not zero jitter. You're
> confused about the difference between "real time", "low latency" and
> "jitter". The whole problem of the old code is that was absolutely
> "deliver it as fast as possible" and that is precisely is what causes
> jitter.

The 'alsarawmidi' slave driver in JACK 2 does not have this problem.
It postpones the delivery of events based on the audio buffer size.
Back in April, when I requested MIDI latency/jitter test results for
the driver, I saw peak jitter results as low as 60 microseconds.

The 'seq' and 'raw' drivers attached to the ALSA audio driver still
suffer from this problem.

-- 
Devin Anderson
surfacepatterns (at) gmail (dot) com

blog - http://surfacepatterns.blogspot.com/
synthclone - http://synthclone.googlecode.com/


More information about the Linux-audio-user mailing list