Re: [ecasound] jack-session (was: Re: RIFF header problem)

Excerpts from Joel Roth's message of 2010-09-16 08:36:21 +0200:
> On Thu, Sep 16, 2010 at 08:15:48AM +0200, Philipp ??berbacher wrote:
> > > When Nama changes Ecasound's playback position under JACK,
> > > it's necessary to:
> > >
> > > 1. stop the transport
> > > 2. change the playback position
> > > 3. allow 0.1s for the system to "settle"
> > > 4. start the transport
> >
> > I didn't deal with this part yet, why does it need to "settle"?
> > Th ecasound-iam manpage mentions a few position related commands that
> > won't work with a connected CS, but all of those control ai or ao
> > independently, so changing the position of the whole CS should work.
>
> > In my old code, when the user issues the stop command, I issue "stop",
> > "cs-setpos 0s" and it doesn't disconnect the jack ports, hence the CS
> > stays connected. Does it need to "settle" for another reason? Why do
> > you need the stop/start?
>
> Here's the thread in which Kai answers my questions on this
> subject. It involves delays related to buffering, which
> manifest when a position change occurs.
>
> http://www.eca.cx/ecasound-list/2009/01/0017.html

Thanks Joel, very enlightening. The thread also scratches on the surface
of one jack transport limitation, namely that it can't be used for
looping, or at least that there are issues. I've seen a very nice page
about jack and especially its limitations somewhere, but I doubt I can
find it easily.

> > There's no arbitrary setting of positions in my code yet, and there
> > are no plans for it yet, so I don't know the details.
> >
> > > That's compared with the situation under ALSA:
> > >
> > > 1. change the playback position
> > >
> > > If a one-line sleep can solve your problems, I think you
> > > should be happy!
> > >
> > > Joel
> >
> > I'd expect it to work the same with jack.
>
> What's amazing about writing software is our expectations
> so frequently need to be revised. :-)

Dunno about revising expectations, but I did notice that mine often were
wrong. I guess it should teach me to not expect stuff, or at least make
fewer assumptions.

> How does that saying go?
>
> In theory, theory and practice are the same but in
> practice they're different.
>
> :-)
>
> Joel

I didn't know that one, nice saying, and apparently quite true. :)

-- 
Philipp
--
"Wir stehen selbst enttäuscht und sehn betroffen / Den Vorhang zu
und alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan
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