[LAD] Some questions about the Jack callback

Fons Adriaensen fons at linuxaudio.org
Fri Sep 19 20:58:58 UTC 2014

On Fri, Sep 19, 2014 at 09:44:44PM +0100, Will Godfrey wrote:

> Just trying to get a clearer understand so hope these aren't too noob-ish.
> If you have several processes wanting to send audio, does the callback go to all
> of them at (essentially) the same time, or does Jack poll them?
> If the former, is it the quickest to complete that gets processed first?
> If the latter, does Jack maintain the same order (assuming none stop) or might
> it change between buffers?

Jack (all versions) will call the client calbacks in an order
that depends only on their connections, i.e. on the way each
client depends on input from any others.

The difference between Jack 1 and 2 is that Jack2 may call
clients in parallel on an SMP machine *if the dependencies
allow this*, while Jack1 will not do this.

> I've a few more questions but they depend on whether either of these
> scenarios is correct! 

Just ask. But be assured that Jack does the right thing

Ciao, (*)

(*) Back in Parma for the WE. When I return to Muenchen
it will be 'Tschuss' instead.


A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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