[LAU] JACK clients at different period sizes

Dominic Sacré dominic.sacre at gmx.de
Fri Sep 16 22:25:41 UTC 2011

On Thursday 15 September 2011 01:06:13 Fons Adriaensen wrote:
> On Thu, Sep 15, 2011 at 12:48:39AM +0200, Dominic Sacré wrote:
> > I have a medium-sized Ardour session with a couple of plugins on
> > most tracks, in which I'd like to record some additional tracks.
> > Due to the number of tracks and plugins, it's not possible to run
> > Ardour/JACK at very low latencies.
> > 
> > The same machine (and the same sound cards) is also used for
> > monitoring for the whole band, using a huge instance of JackMix.
> > This needs to be run with as little latency as possible (128
> > frames per period, tops).
> > 
> > How can I solve this dilemma? Ardour's latency doesn't really
> > matter to me, as long as newly recorded regions are properly
> > aligned with existing material.
> > 
> > It might also be an option to run Ardour on a different machine via
> > netjack, but as far as I can see the period size of a netjack slave
> > is tied to that of the netjack master. It also seems doubtful that
> > Ardour would be able to do correct latency compensation in this
> > scenario...
> > 
> > Any suggestions? Is there any way to run run a second, high-latency
> > JACK server piggy-back on a low-latency server?
> If you can't decrease the period size, the the only option
> is do the monitoring *for the new tracks being recorded*
> in hardware, using either a 'real' mixer or the one that
> may be provided by your sound card. If you have RME gear
> hdspmixer is the solution - this use case is why it exists.

The sound cards are a pair of M-Audio Delta 1010, and their hardware 
monitoring capabilities are quite limited.
We used to have a 'real' 24-channel mixer for all our monitoring, but 
decided to basically replace it with a PC running JACK, which is not 
just cheaper, but also much more flexible. And the whole setup actually 
worked surprisingly well until now...

A very small hardware mixer just for monitoring the tracks being 
recorded is an interesting idea...

> The latest Ardour 2 should take care of latencies - see
> Paul's post of today.

Thanks for mentioning this, I probably would have missed it otherwise. I 
*think* latency correction worked correctly for me in Ardour 2.8.11, but 
I'll definitely give the latest SVN a try.



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