Skype Sound and Audio Set-Up
PC Running Linux
Commands you are meant to type throughout this guide should be entered in terminal window (either konsole or gnome-terminal or xterm or whatever else terminal you happen to have at hand).
Available sound options under Linux
OSS (Open Sound System)
The oldest sound support available in Linux. This type is natively supported by Skype. To use it you only need to select DSP device for your sound card. On most systems it will be /dev/dsp (the default Skype setting). If you have multiple sound cards you might need to select an additional device designated as /dev/dsp1, /dev/dsp2 or /dev/dsp3 in Skype setup.
Be sure to enable microphone input in the audio mixer setting: use aumix, kmix or gnome-volume-applet to enable and choose it as input source.
Here's the example for kmix applet:
Check green mark here to turn on microphone input (it is off in this picture).
Check red mark here to set input capture source to mic (it is now selected in this picture).
Some sources (e.g. futt Linux sound FAQ) recommend turning capture off. Another option is to set it to mic input and only if it does distort sound, then turn it off. Besides, on some hardware its impossible to turn capture off at all. This option seems to have different effect on different hardware.
ALSA (Advanced Linux Sound Architecture)
ALSA is more modern than OSS. Currently, Skype does not natively support ALSA, so you will need to install ALSA OSS emulation layer in order to use ALSA devices in Skype.
You should have snd-pcm-oss and snd-mixer-oss modules in your kernel, either loaded separately or compiled in as part of the kernel.
You can check for presence of these modules by issuing (as root user) the following command:
lsmod
If you don't have these modules, try to load them. Type (again as root user):
modprobe snd-pcm-oss
modprobe snd-mixer-oss
If you get errors executing these commands, try to upgrade your kernel or consult your unix guru and/or support forums for your Linux distribution. You may also post in the Skype for Linux forum.
Using Skype with OSS emulation is same as for pure OSS driver, see above section about OSS on more information.
With 2.4 and newer series kernels, you may have more luck with ALSA drivers and OSS emulation, rather than with pure kernel OSS. Just install latest alsa-driver from the ALSA project (if your kernel has OSS as module, which it does for the most stock kernels).
If you have ALSA with dmix (kernel stream mixer) enabled, running Skype should be no different from setup described above.
When using motherboards with 5.1 sound support, be sure to turn off "Mic as Center/LFE" and "Line as surround" options in the mixer. These options might not be present in pure OSS, you should be using ALSA with such motherboards anyway.
aRts (Advanced Real-time Synthesizer)
This is KDE default. Whenever your aRts sound works, it means that Skype should, too. The only trick is to run Skype through artsdsp program.
You should start Skype as follows: in the directory where skype executable is located, type:
artsdsp -m ./skype
If your microphone does not work, or you get Segmentation fault when calling, check the full-duplex setting of aRts - in KDE Control Center | Sound & Multimedia | Sound System on Hardware tab there should be a Full duplex option, set it to on ("[x]"), then restart aRts and Skype.
If you hear echo and using aRts, try to decrease your aRts sound buffer size, go to Control Center | Sound & Multimedia | Sound System and decrease Sound buffer size to something under 200ms on General tab in Skip Prevention section.
ESD (Enlightened Sound Daemon)
This is GNOME default. Run Skype through esddsp pipe to enable sound. Do it like this (again, assuming you are in the directory where skype executable resides):
esddsp ./skype
Be sure to run esd daemon using "esd -d /dev/dsp" because on some distros (e.g. Gentoo) the esddsp wrapper checks for parameters present to esd daemon and won't detect the daemon if there are no parameters.
GStreamer, NAS (Network Audio Server), other
There's currently no way to enable Skype sound through GStreamer. You better disable GStreamer and use direct ALSA or OSS method described above.
NAS, NMM and other relic audio servers are most probably unsupported, so your best choice is to stop them and use ALSA or OSS driver directly, see above for detailed instructions.
Testing things
There's a great partner for a chit-chat conversation, called "echo123". It is a Skype robot who lets you test your sound setup without disturbing anyone. Just call the robot and follow the instructions. You can test hearing other party and saying to other party - what you say within a 10 seconds interval the robot will play back to you.
Advanced topics
Using skype_dsp_hijacker to specify different devices for playback and record.
Sometimes you have to use different dsp devices for playback and for recording, one such example is USB speakers (on /dev/dsp1) and conventional mic (on /dev/dsp). While Skype does currently not natively support this, there's a tool which lets you to "hijack" a /dev/dsp device addressed by Skype and substitute /dev/dsp1 instead.
skype_dsp_hijacker is available at http://195.38.3.142:6502/skype/. Just follow the instructions to build and install it, then run Skype as described in the skype_dsp_hijacker manual.
Things (not) to worry about
"Sound device is not defined"
When Skype says "Sound device is not defined" this only means that sound configuration option in Skype does not designate any specific device, so Skype uses default /dev/dsp. It has nothing to do with your (or someone else's) hardware sound device, so don't worry.
Headset
We recommend using a headset/headphones and not speakers with your microphone, because sometimes speakers can cause "positive feedback loop" which can lead not only to echo, but to uncomfortable high-pitched noise.
Thanks
A big thanks to everyone on the Skype for Linux forum - much of the info has been collected and organized by futt and bonbons. The forum is also a good place to get up-to-date info and responses from Skype for Linux user community.
