Re: [LAD] JACK transport timebase and its callback

From: Paul Davis <paul@email-addr-hidden>
Date: Mon Oct 20 2008 - 14:42:48 EEST

On Mon, 2008-10-20 at 13:33 +0200, Julien Claassen wrote:
> Hello!
> I just read through the JACK transport section in the JACK reference again.
> If you want to be timebase-master you can (or must) supply a callback function
> to update the time-info.
> Does my program need audio thread (a process function?)

No. JACK will call your timebase callback at the right time.

> Which timing source
> is used to update the time?

that is up to you. it could be MTC, some other form of timecode, a
wallclock, NTP or whatever you want. keep in mind that JACK does not
support varispeed (a decision made long ago to avoid burdening every
JACK-transport app with very difficult implementation issues).

> Does my program provide it or does JACK provide it
> and my program only really kicks in when I want to relocate (jump to another
> position)?

no, if your client elects to be time master then it is responsible for
updating the time every process cycle.

> I am correct in assuming, that my code doesn't have to be multithreaded (at
> least not look multithreaded) if I want to use the JACK transport interface
> (control and timebase)?

JACK will create a thread for you, you just supply the callback. The
callback will be called from the JACK-created thread, so you need to be
aware of this.

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Received on Mon Oct 20 16:15:03 2008

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