Hi, I've been searching for a Phonon backend that provides decent uptodate Jack support and I'm not sure where to turn to to ask about such a thing. It occurs to me that qtractor may have some code that could be used as a basis for a Phonon-Jack backend and/or perhaps Rui or someone else may have some thoughts on this seeing that qtractor, and of course qjackctl, compile and run on qt-snaphot (4.5) so is in the general ball park.
Yes I know Phonon should provide video services too but that could be provided by ffmpeg with a bit of a Qt interface for displaying video. All I know is I dislike gstreamer and I don't think xine-lib or the mplayer/vlc backends will have any "decent" jack support so perhaps a more direct Jack backend for Phonon, in conjunction with some direct video backend, might be worth looking into?
I would love to see qjackctl automatically come up when configuring the audio side of some Phonon enabled application.
Re: Phonon backend that provides Jack support
Now that you ask, I'm seeing a JACK device entry on the Sound System Configuration of my KDE 4.1.3. I've tested it, by putting it on the top of my output device preferences and after a very cursory hearing it seems to do the job, as long as jackd is currently running alright. It doesn't make it to start jackd (or qjackctl) on its own, but it's a good sign anyway :)
I suspect, however, that this listed JACK output device is provided by xine-lib and it is not a genuine JACK backend. And as a matter of fact, Matthias (phonon's architect) once or more times have said there's no way or point in having a JACK backend for Phonon, due to simple fact that a Phonon backend must be capable to (de)encode all or most types of media, audio and video. JACK only does raw audio and thus can only serve as an audio output device on behalf of some other media streaming library (eg. xine or gstreamer). And that closes the case I'm afraid ;)
One other thing: I really can't say how much it is desirable to have those nasty desktop sounds and notifications (think of IM:) injected on my best take of a recording I was deeply engaged ;))
Cheers
That KDE4 Jack option only
That KDE4 Jack option only appears when xine-lib is used so it's completely unavailable for Qt only projects because Qt can't inlcude xine-libs for licensing reasons. Qt-only apps are my concern as I am trying to put together a simple Qt-only (or mostly) desktop system that actually features qtractor and qjackctl.
I can appreciate Matthias point of view but, in a way, xine-lib is just a wrapper around a Jack audio backend... or proxy middleware on behalf of a Jack audio backend. I'd just like to get rid of most of the middleware not related to supporting Jack+ALSA on the audio side. Related is a video backend and I'd like to see a more direct ffmpeg backend with a simple Qt display mechanism (ffplay uses SDL but is only 55K in size). The phonon-vlc backend would be a close starting point, for the video side at least.
As for misdirected sounds, the phonon kcfg already allows for sending audio types to different targets and qjackctls patchbay is the most powerful reason I want a generic Jack backend for Qt apps in the first place :-)
To me, Jack is to audio as OpenGL is for desktop/video usage and cheap modern motherboards come with OpenGL capable onboard GPUs and often have 24/96 x 8ch audio at ~95db. I don't see the point of NOT taking advantage of both (in the context of a "new" lightweight desktop that will take years to mature). I want your qjackctl patchbay as a fundamental part of a Qt based desktop system for my use, not as a "professional" add on, so if that means trying to add a Jack backend to phonon (the official way to support such things for Qt) then so be it. The point that such a system does not exist is my itch. Please excuse my rant on your forum :-)
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