Re: [Jack-Devel] Using Jack

On Thu, Mar 20, 2014 at 9:12 PM, Yves Perron <[hidden]> wrote:

>
>
> *Hi Paul, I'm getting there, thanks again for your devotion to this thread*
>
> As has been mentioned already, the Windows version of JACK uses the same
> system that was created for POSIX systems to enable autostart. This system
> is what Ardour and Mixbus both use:
>
> That is interesting,
>
> write the command to $HOME/.jackdrc and when jack_client_open() is called,
> if there is no server, one will be created using the command given in that
> file.
>
> While that seem to be a solution, it would be nice if you could elaborate
> on this.
>
> What command?
>

the command that will start a JACK server.


> Is that command called just before jack_client_open()?
>

it is not "called" at all. the command is placed into $HOME/.jackdrc and
then libjack reads it from there and starts the server using the command it
finds in the file.


> Where is $Home?
>

on windows? no idea. read the source code.


> Of course, the format of the file is different for jack2 than for jack1,
> but since jack1 doesn't run on windows, no problem: one component of the
> command per line.
>
> One component of the command per line? Any example of this I could chew on?
>

i already told you that qjackctl also writes to this file.


> QJackctl also creates this file to store the last configuration in.
>
> What is the file name? and where is it stored?
>

on windows, no idea. i gave you a hint ...


> You could get the command correct using QJackctl and then just re-use the
> file contents in the future.
>
> What you are trying to do is unconventional, and not intended to be easy,
> nor is it documented or planned for use by random developers.
>
> jack_client_open() is already starting a server automatically if none
> present, what is unconventional about setting custom options before it
> starts? Otherwise it makes it useless to start a vanilla server... in my case
> at least.
>
yes, in your case, which is odd and unusual and you seem to want it to work
with very little effort on your part.

There are ways to make it work, but as I've tried to make it clear, you are
> really on your own trying to accomplish this. The facilities for starting
> the JACK server from within a client are a mostly hidden element of the API
> and intended for people writing control applications NOT for people who
> wish to focus on a normal client.
>
> So what is the point of starting the server automatically in the first
> place? That's pretty much the source of my confusion.
>
so that clients that need the server will just find it running, with the
same parameters as it was last started with. clients can explicitly request
that jack_client_open() should NOT do this if they prefer.


> Could you define Control application? I mentioned previously: "As a
> second phase, I'll use my app to sync, send/receive data from/to other
> clones of my app through a local network. "
>

a control application is an app that exists for no purpose other than to
configure and control JACK. qjackctl is an example of one such application.
JackPilot on OS X is another. Carla on Linux is another. patchage on Linux
is another (though this is purely a patchbay, it does not offer server
startup+configuration). another way to put it is "an application that has
no JACK ports and does not register a JACK process callback".


> Would that classify as control application? If yes, that's clearly what I
> want. I want to make a controller application.
>
it does not.


> This is why we are focusing on this. You are not only using JACK on the
> least-used-with-JACK platform, but wanting to do something quite
> unconventional, when in fact all of your goals could be achieved without
> dealing with JACK at all.
>
>
>
> Why would a jack_server_start("with midi support") function be so
> unconventional? Plus, using jack_options_t with all the supported init
> options would be beautiful. I don't understand what you are trying to
> prevent developers to play with.
>

we've explained this several times. JACK was not designed to be used in the
way you want to use it.

if you want full control over the server startup, use the control API to
start the server. if that is too complex, use $HOME/.jackdrc. If neither of
those work for you, then don't use JACK at all.


conventionally JACK is started by the user as a separate step from starting
any client applications. the cases where this is not done (e.g. Ardour or
Mixbus) have been coded by people who know a great deal about JACK and have
had to deal with a variety of subtle issues with doing this.


there is a  LOT of (non-windows) example code, documentation of the control
API ... you are going to have to start digging because nobody is going to
hand this to you on a plate.


--p

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