JACK: output from speakers but not from headphones.

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christophski
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I have a Sager 5160 laptop running Ubuntu 11.04. I am having a problem with JACK where sound comes out of the speakers fine, but when I plug headphones in the speakers cut out like they are supposed to, but nothing comes through the headphones.
The system works fine when I am just using the standard Ubuntu sound system so I'm not really sure what's going on, can anybody help?

paul
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unfortunately, your understanding of how the sound in your laptop works is slightly flawed. the switch between output to the headphones and the speakers is not done by the hardware or the device drivers, but is left to other software. the device driver provides information that a headphone jack was inserted or removed, but its up to some other level of software to then change the state of the hardware's mixer to alter the routing appropriately (or not at all). PulseAudio, a desktop sound system/server, will do this for you because it considers that part of its job.

JACK, however, does not consider this part of its job and is not interested in managing the state of your h/w mixer for you. JACK wasn't designed to be used with consumer hardware that has this kind of design (although it does work with it for the most part), and it (almost) never does anything to alter the state of the h/w mixer that controls audio flow because we assume that, since you are using pro-audio and music creation applications, you have set it up the way you want it and you intend for it to remain that way.

older laptops (and even some desktop) soundcards did this output switch in hardware (e,g, my old HP Pavilion), but in recent years it has become more and more common to make the switch the responsibility of software. JACK just isn't that software. if you want to do it by hand, you will need to use an application that controls the h/w mixer. alsamixer (run from a terminal window) is ugly but very functional. there are a few other GUI apps that do similar things but i can't recommend any of them (unfortunately).

christophski
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Thanks for the comprehensive reply paul, I thought it might be something like that, I was hoping I'd be able to use my internal soundcard for some quick editing when I'm about but it looks like I'm going to have to use an external card. Thanks anyway!
I will check out alsamixer anyway, see if I can get anything going.

EDIT: I found the solution, the headphones are presented as outputs 3 & 4 under system in the connections window. Thanks for your help!