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I just finished one of those long fights we sometimes accept just to get some really minor problem solved. I got myself an usb microphone. After successfully getting it to run under alsa and recordmydesktop i went and looked for some graphical sound level meter (or however that is correctly named). There is apparently no such thing in kde and a google search was unsuccessful too. Some pulseaudio based solution ... thanks but no thanks. And some jack based ones.

So i finally looked into jack. I remembered from some attempts long time ago the need for realtime kernel. Not anymore. So i decided to give it a try. Feel free to learn from my feeble (and successful) adventures that follow.

After installing the needed packages i tried to start jack. It complained the sound device is busy. The culprit is obviously phonon somehow. Since i tried unsuccessfully before to free the sound device while keeping a kde session running i didn't even try. After adding a file with the following content to $HOME/.kde/Autostart i rebooted. Make sure you have those programs btw.

#!/bin/sh
killall timidity
killall jackd
 
cd /tmp
nohup qjackctl --start >/tmp/${LOGNAME}-qjackctl.log &
sleep 2
nohup timidity -iA -Oj >/tmp/${LOGNAME}-timidity.log &

I do not know exactly at which point those scripts are called, but my hope was before any kde daemon graps the sound device. And it works. Kinda. On login qjackctl always tells me jackd has crashed. But simply starting it again workd. So i had a running jackd daemon but obviously no kind of sound. Phonon - btw. didn't we try to get rid of those kind of names? - noticed that it was no longer able to use the current default sound device but that has to wait. To make sure that jack works first two tools are important. First qjackctl which embedded itself into the systray and jack_metro. First raise qjackctl from the systray and open up the connections dialog. Then from a command line start jack_metro -b 60. That creates a beep every second. Now lets try to make it hearable. You should see a metro entry on the left side of the qjackctl connections dialog. Connect that to system:playback_1 on the right sight by drag and drop. You can hear the beep? Great. If not you have to play with the preferences in qjackctl. Especially on the first tab, right side in and out channel (sorry translated form german here). There is a '>' button on the right side. Select different devices and restart jackd. Attention: Make sure jackd is really stopped after clicking on stop in qjackctl. That does not work here. Kill it if not.

Now you should have sound. If not it is obviously a good idea to stop here and undo what is done so far. No luck today.

Back to phonon. There is no phonon-jack backend so we have to find a way to take a longer route. My google fu brought up Jack Faq. The section "How can I play audio from .... via JACK?" is interesting. For my system it was the Routing GStreamer audio via JACK part. Hop over there for the needed steps i won't repeat them here. The gconf part was kinda annoying (didn't someone complain somewhere of kde apps pulling in hole mountains just to work?) but it worked. A gstreamer only check is done with gst-launch -v playbin uri=file:///my/music/file .

Back to phonon. I needed some time to figure out i had to go to kcmshell4 phonon and select the "Jack Audio Connection Kit" Device for all audio playback (Do not forget the "Apply Device List To ..." button). After restarting a phonon enabled application it should work., And it did.

That was to easy till now. If things go that smooth i get irritated.

Next thing is how to get alsa applications up and running again. Like flash for example. There is a nice thing called "The Alsa Jack Plugin". and it is nicely described how to setup that one in How do I route audio to/from generic ALSA-using applications?. This did work to sometimes. Then stopped to work. When flash once again (is does that from time to time) froze my complete X-Server so i had to reset i asked why i care. Other apps work great as you can check with aplay.

Talking about arecord. If you want to record audio that should work out of the box too. Just make sure the same conditions are met as when trying to record with alsa. The channel is active and set to recording (this is reset very often. Double check in case of trouble). Use either alsamixer or kmix to do that. In kmix notice the button on the left of the tab bar to add more hardware tabs and the channels entry from the context menu to make sure you see all needed channels (That cost me some time some weeks ago :) ).

If your micro shows up in the connections dialog just connect it to the output and you should hear yourself.

All of that btw. for this small command: meterbridge -t ppm [port]. Either specify a port on the command line or connect manually. A graphical sound level meter. Hooray.

Unintended side effects. Try jack-rack. Has nice sound effects. And jackeq. If you understand the latter one blog about it. I don't. Audacity is nice too.

Have fun