[LAD] accepted use of sync callback

Lieven Moors lievenmoors at gmail.com
Sat Mar 26 15:45:51 UTC 2011

Hi Paul,

Thanks for your reply.
I'm not sure my program would satisfy the realtime constraint.
But I'll have a look at both options again...



On Sat, Mar 26, 2011 at 11:18:20AM -0400, Paul Davis wrote:
> On Sat, Mar 26, 2011 at 11:08 AM, Lieven Moors <lievenmoors at gmail.com> wrote:
> > Hi everybody,
> >
> > I have a question.
> >
> > I'm trying to figure out how to deal with transport locate changes
> > in my arpeggiator "flarps". I am generating MIDI events only when
> > necessary, so I'm not able to rewind the state of the program.
> > I only keep track of Note-off messages, because they can be sent
> > out in the future, to allow overlapping notes. All the MIDI notes
> > are calculated relative to each other. So I keep track of time
> > internally.
> >
> > So I only need to know the first frame of the period,
> > when somebody does a jack_transport_locate, and I need to know
> > when this happens so I can initialize the program state.
> >
> > My question is, if it would be acceptable to use the sync callback
> > to do this, because strictly speaking, my client wouldn't be a
> > slow sync client.
> its entirely appropriate.
> > Is there a more preferable way to do this, or should I do major
> > redesign, and use the time jack provides with each period directly.
> if you can do this in a way that still more or less meets the realtime
> constraint:
> 	T = F(nframes) + C
> (that is, time per process cycle is a linear function of the nframes
> value, plus a constant)
> then simply doing it in every process call is fine. if not, then use
> the sync callback.

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