Understanding JACK

fflarex · 2009-10-29 05:01:12

Does JACK have any benefits for end users, or only for developers and audio professionals? I've tried finding non-programming information on JACK without success, and I guess I just don't understand it. Can anyone explain it or point me to a link with a good explanation, hopefully with concrete examples?

ngoonee · 2009-10-29 06:52:48

If you don't need it, you don't need it .

If you want to use a JACK-only app, then you have to have it. For apps which can do alsa, use alsa.

The main purpose of JACK is low-latency, which is primarily only useful for audio work which is more complicated than one/two track recording (for example, recording over a previous recording, with live real-time effects applied.

fflarex · 2009-10-29 13:55:14

So why is JACK support compiled into so many packages in the repos then? There's no way there are enough average users doing that kind of thing. There's got to be some other benefit, no?

Dieter@be · 2009-10-29 14:12:04

nope. basically what ngoonee said. and also it provides flexible routing between app's inputs/outputs and hardware.

ngoonee · 2009-10-29 23:08:29

fflarex wrote:

So why is JACK support compiled into so many packages in the repos then? There's no way there are enough average users doing that kind of thing. There's got to be some other benefit, no?

Most times its compiled in to applications because applications which provide JACK support tend to rely on it for functionality. However those apps are audio dev applications anyway. I don't think you'll find any music players compiled for Jack, for example (mpd doesn't, I'm very sure, even though it is capable). Hydrogen and Ardour, on the other hand, must work with Jack.

I'm curious about the 'so many packages in the repos' statement. Care to back that up with numbers and names?

skottish · 2009-10-29 23:16:59

ngoonee wrote:

I'm curious about the 'so many packages in the repos' statement. Care to back that up with numbers and names?

There are 19 programs that depend on it in the official repos (i686):

http://www.archlinux.org/packages/extra … ction-kit/

fflarex · 2009-10-30 02:23:52

Maybe I didn't have a good sense of the numbers... But I tend to switch out the applications I use quite a lot, and it always seems to be installed as a dependency of something. Probably gstreamer0.10-bad-plugins, vlc, and mplayer.

skottish · 2009-10-30 02:35:12

fflarex wrote:

Maybe I didn't have a good sense of the numbers... But I tend to switch out the applications I use quite a lot, and it always seems to be installed as a dependency of something. Probably gstreamer0.10-bad-plugins, vlc, and mplayer.

I think that 19 apps is a very significant number considering how intertwined multimedia is on Linux. The only reason why I looked is that it seems like I run into it a lot also while digging though configuration files.

fflarex · 2009-10-30 04:05:29

19 is a high number, but most of those are "audio dev" applications, as ngoonee put it. If you ignore those, then you are pretty much only left with mplayer, vlc (since it depends on fluidsynth), gstreamer0.10-bad-plugins, and moc. So we're left with only 4 packages that probably don't need JACK support (I might have missed a few less oft-used packages that depend on something that depends on jack). These packages do probably effect quite a lot of users who don't need JACK though.

Last edited by fflarex (2009-10-30 05:06:45)

owain · 2009-10-30 11:20:51

Audacity, for one, can be compiled without Jack support, so there's always that option. I suspect this is true of other applications out of those 19, too.

ngoonee · 2009-10-30 15:22:17

owain wrote:

Audacity, for one, can be compiled without Jack support, so there's always that option. I suspect this is true of other applications out of those 19, too.

Audacity's Jack support sucks for me, anyway. And it doesn't depend on Jack, IIRC. But then again I always have jack installed, so I may be wrong.

kayosiii · 2009-11-07 04:46:03

Jack the only audio system supported by firewire based soundcards. If you happen to be using one of those (like me) then no jack means no sound.

I single biggest issue with Ubuntu is that they remove jack support for all core apps meaning that if I want to use VLC, or gstreamer or even ALSA I have to recompile those packages with jack support. This is a massive PITA.

Jack is designed with professional audio in mind. It is....
1) optimised for low latency - minimal time between audio arriving in the computer and leaving through the speakers. This is particularly important for live performance applications.
2) Fixed latency - will not delay sound if computer can't process it fast enough. Will somewhat take over your computer to assure that other processes don't interfere with the delivery of sound packets.
3) Flexible audio routing -- audio from app A can be routed into audio from app B
which can be Routed into app C. App D can monitor the signal comming out of App B and can easily be moved to anywhere else in the signal chain. Patchage is the best application that I know of for doing jack routing. An example of this might be to hook up a music player into an effects rack that has an equalizer loaded.
4) Synchronised playback between applications - Application A is set to master application B and C are set to slaves. If I press play in Application A application B and C should start playback from the same point in the timeline.

Arch Linux

#1 2009-10-29 05:01:12

Understanding JACK

#2 2009-10-29 06:52:48

Re: Understanding JACK

#3 2009-10-29 13:55:14

Re: Understanding JACK

#4 2009-10-29 14:12:04

Re: Understanding JACK

#5 2009-10-29 23:08:29

Re: Understanding JACK

#6 2009-10-29 23:16:59

Re: Understanding JACK

#7 2009-10-30 02:23:52

Re: Understanding JACK

#8 2009-10-30 02:35:12

Re: Understanding JACK

#9 2009-10-30 04:05:29

Re: Understanding JACK

#10 2009-10-30 11:20:51

Re: Understanding JACK

#11 2009-10-30 15:22:17

Re: Understanding JACK

#12 2009-11-07 04:46:03

Re: Understanding JACK

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