[LAD] New proposal for the jackd/jackdbus mess

Stéphane Letz letz at grame.fr
Wed May 20 09:32:12 UTC 2009

Hi all,

New much simplified proposal, should be "Fons compatible", hopefully  
"Nedko compatible" (with little work), "Paul one package only  
compatible", others "keep it simple compatible"...

The first "big" conceptual change compared to the current SVN state is  
this new "control IPC" scheme. That is the so called control API can  
be used on client side also. The other conceptual change is that  
"jackd" process is supposed to be an "always running" daemon that  
defines an IPC entry point to be used from "clients". This daemon does  
not "automatically" starts the server (as it does now), but will  when  
requested (either by the "jackd" code directly using C API ) or by the  
request of external control font-end using IPC.

1) Server side:

- libjackserver.so contains:  server code + C control API  + "new" IPC  
control API (server side) +  C Jack API  + IPC Jack API (server side)

- jackd executable is linked with libjackserver.so  (nothing new here)

- backends (ALSA, dummy...) are linked with libjackserver.so  (nothing  
new here)

- a "standalone" client (that wants to embed the server in it's  
process) is linked with libjackserver.so and directly uses the C  
control API  to control/start the server and C Jack API to be a client  
(nothing new here).

2) Client side:

- libjack.so contains :  "new" IPC control API (client side) + IPC  
Jack API (client side)

- clients are linked to libjack.so (nothing new here)

- new control front-end (jackdbus, jackOSC...) are linked to  
libjack.so: they control the server using the IPC control API (client  
side), they can be regular clients using IPC Jack API (client side) to  
deal with connections management and so on...

- a "default" centralized state for the server is always kept in ~/ 
jackdrc. When a client wants to auto-start, this "default" state is  
used. (this is important to keep in mind)

- libjack may have to start the "jackd" executable using the fork+exec  
way, or the "jackd" process is an "always running + relaunch" process  
(this has to be more defined later on...)

- Qjakctl stays as a regular client, it can still start the "jackd"  
process as usual. It can keep its own way of keeping multiple  
configurations as it does now.

- more sophisticated control front-end (jackdbus, jackOSC...) are now  
regular clients. They can use the IPC control API (client side) for  
more sophisticated control of the server. As regular clients, they  
access the API to control connections... and so on. The important  
thing is that those clients are *obliged* to deal with this "default"  
centralized state. Even if they deal with multiple configs in a new  
format  (XML...) they are supposed to always put a "default" state in  
~/jackdrc for the client "auto-start"  feature to continue working.

- Ardour can still do it's server control mess on its own... ((-:

3) General:

- a single jack2 package is needed. It contains the "jackd" daemon/ 
server are before.

- "jackdbus" is now conceptually separated from the Jack source code.  
It only uses jack.h + control.h and is linked to libjack.so as any  
regular client. It can be distributed separately as a more  
sophisticated control front-end available, or be available in the  
jack2 package.

- old fashion users can keep their habits

- new "D-Bus aware" guys can explore new fields...

This scheme seems to hopefully solve most of the problems we had, and  
requires only a bit of change for the "jackdbus" front-end to continue  
working, but not much.



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