Difference between revisions of "Skype"

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==Installing and Running Skype==
 
==Installing and Running Skype==
{{Package Official|skype}} is available in <nowiki>[</nowiki>[[AUR User Guidelines#.5Bcommunity.5D|community]]] for i686 systems and <nowiki>[</nowiki>[[Arch64 FAQ#Multilib Repository - Multilib_Project|multilib]]] for x86_64 systems [http://www.archlinux.org/news/508/] or as [http://aur.archlinux.org/packages.php?ID=18312 bin32-skype-oss] for the OSS sound system in the AUR. Enable the appropriate repository in {{Filename|/etc/pacman.conf}} and then use [[pacman]] to install Skype,
+
{{Package Official|skype}} is available in <nowiki>[</nowiki>[[AUR User Guidelines#.5Bcommunity.5D|community]]] for i686 systems and <nowiki>[</nowiki>[[Arch64 FAQ#Multilib Repository - Multilib_Project|multilib]]] for x86_64 systems [http://www.archlinux.org/news/508/] or as [http://aur.archlinux.org/packages.php?ID=18312 bin32-skype-oss] for the OSS sound system in the AUR. Enable the appropriate repository in {{ic|/etc/pacman.conf}} and then use [[pacman]] to install Skype,
 
  # pacman -S skype
 
  # pacman -S skype
  
Line 30: Line 30:
 
  # apparmor_parser -r /etc/apparmor.d/usr.bin.skype
 
  # apparmor_parser -r /etc/apparmor.d/usr.bin.skype
  
Now you can run Skype restricted but as your own user. Denials are logged in {{Filename|messages.log}}.
+
Now you can run Skype restricted but as your own user. Denials are logged in {{ic|messages.log}}.
  
 
===TOMOYO===
 
===TOMOYO===
Line 45: Line 45:
 
Enter the details for the new user (assumed login name: "skype"). If you created the default "skype" group and want to keep "skype" outside the "users" group, enter "skype" when the wizard asks for the initial group. As additional groups we need "audio,video,pulse-access,pulse-rt".
 
Enter the details for the new user (assumed login name: "skype"). If you created the default "skype" group and want to keep "skype" outside the "users" group, enter "skype" when the wizard asks for the initial group. As additional groups we need "audio,video,pulse-access,pulse-rt".
  
Now add the following line to {{Filename|/home/skype/.bashrc}}:
+
Now add the following line to {{ic|/home/skype/.bashrc}}:
 
  export DISPLAY=":0.0"
 
  export DISPLAY=":0.0"
  
At last we define the alias (e.g. in {{Filename|~/.bashrc}}):
+
At last we define the alias (e.g. in {{ic|~/.bashrc}}):
 
  alias skype='xhost +local: && su skype -c skype'
 
  alias skype='xhost +local: && su skype -c skype'
 
Now we can start Skype as the newly created user simply by running {{Ic|skype}} from the command line and entering the password of the user skype.
 
Now we can start Skype as the newly created user simply by running {{Ic|skype}} from the command line and entering the password of the user skype.
Line 60: Line 60:
 
I noticed that the newly created user is able to read some of the files in my home directory because the permissions were a+r, so I changed them manually to a-r u+r and changed umask from 022 to 066.
 
I noticed that the newly created user is able to read some of the files in my home directory because the permissions were a+r, so I changed them manually to a-r u+r and changed umask from 022 to 066.
  
In order to restrict user "skype" accessing your external drive mounted in {{Filename|/media/data}} for instance, make sure first that "skype" does not belong to group "users" (if you used the default group "skype", everything should be fine), then change the accesses on the mount point:
+
In order to restrict user "skype" accessing your external drive mounted in {{ic|/media/data}} for instance, make sure first that "skype" does not belong to group "users" (if you used the default group "skype", everything should be fine), then change the accesses on the mount point:
 
  # chown :users /media/data
 
  # chown :users /media/data
 
  # chmod o-rwx /media/data
 
  # chmod o-rwx /media/data
Line 74: Line 74:
  
 
===Skype ALSA Sound (2.0+)===
 
===Skype ALSA Sound (2.0+)===
Sound should work out of the box, if not you can select a sound device to use in Skype options. If you have problems with Skype blocking your sound device, you only need to add the following to your {{Filename|~/.asoundrc}}
+
Sound should work out of the box, if not you can select a sound device to use in Skype options. If you have problems with Skype blocking your sound device, you only need to add the following to your {{ic|~/.asoundrc}}
 
  pcm.dmixout {
 
  pcm.dmixout {
 
   # Just pass this on to the system dmix
 
   # Just pass this on to the system dmix
Line 101: Line 101:
 
  # pacman -S alsa-oss
 
  # pacman -S alsa-oss
  
Add the following to {{Filename|~/.asoundrc}}. If the file does not exist yet, just create it! (Many thanks to Lorenzo Colitti for figuring this out!)
+
Add the following to {{ic|~/.asoundrc}}. If the file does not exist yet, just create it! (Many thanks to Lorenzo Colitti for figuring this out!)
  
 
  # .asoundrc to use skype at the same time as other audio apps like xmms
 
  # .asoundrc to use skype at the same time as other audio apps like xmms
Line 171: Line 171:
 
  The dmix plugin supports only playback stream
 
  The dmix plugin supports only playback stream
  
then add the following to {{Filename|.asoundrc}}:
+
then add the following to {{ic|.asoundrc}}:
  
 
  pcm.asymed {
 
  pcm.asymed {
Line 190: Line 190:
 
Optionally you can make a script to start Skype:
 
Optionally you can make a script to start Skype:
  
As root, create the file: {{Filename|/usr/bin/askype}}
+
As root, create the file: {{ic|/usr/bin/askype}}
  
 
  # Little script to run Skype correctly using the modified .asoundrc
 
  # Little script to run Skype correctly using the modified .asoundrc
Line 204: Line 204:
 
You can also fix the menu entry so you can start Skype from the your window manager's menu:
 
You can also fix the menu entry so you can start Skype from the your window manager's menu:
  
Edit the file: {{Filename|/usr/share/applications/skype.desktop}}
+
Edit the file: {{ic|/usr/share/applications/skype.desktop}}
  
 
  [Desktop Entry]
 
  [Desktop Entry]
Line 232: Line 232:
  
 
===Skype crashes shortly after login===
 
===Skype crashes shortly after login===
If Skype crashes shortly after logging in, changing the rights for {{Filename|libpulse.so.0.12.4}} (minor version might differ) and {{Filename|libpulse-simple.so.0.0.3}} might fix the issue.[https://bugs.launchpad.net/ubuntu/+source/ia32-libs/+bug/646862/comments/14]
+
If Skype crashes shortly after logging in, changing the rights for {{ic|libpulse.so.0.12.4}} (minor version might differ) and {{ic|libpulse-simple.so.0.0.3}} might fix the issue.[https://bugs.launchpad.net/ubuntu/+source/ia32-libs/+bug/646862/comments/14]
  
 
  # cd /usr/lib
 
  # cd /usr/lib
Line 238: Line 238:
 
  # chmod ugo-r libpulse-simple.so.0.0.3
 
  # chmod ugo-r libpulse-simple.so.0.0.3
  
64bit users might have to cd to {{Filename|/usr/lib32}} instead.
+
64bit users might have to cd to {{ic|/usr/lib32}} instead.
  
 
===I can receive multiple audio streams, but I can only send one===
 
===I can receive multiple audio streams, but I can only send one===
Line 254: Line 254:
 
  LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so skype
 
  LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so skype
  
To make it running from DE menus and independent of Skype updates, you can add alias (e.g. in {{Filename|~/.bashrc}}):
+
To make it running from DE menus and independent of Skype updates, you can add alias (e.g. in {{ic|~/.bashrc}}):
  
 
  alias skype='LD_PRELOAD=/usr/libxx/libv4l/v4l1compat.so skype'
 
  alias skype='LD_PRELOAD=/usr/libxx/libv4l/v4l1compat.so skype'
Line 266: Line 266:
  
 
===Skype does not use my GTK theme, even though other QT apps do===
 
===Skype does not use my GTK theme, even though other QT apps do===
Recent versions of Skype allow you to change the theme via the Options menu. However, selecting the GTK+ option may not work properly. This is probably because you do not have a 32-bit theme engine installed. Try to find the engine your theme uses in the multilib repository or the [[AUR]]. Once installed, it will still not work unless you have a 32-bit version of GConf installed. You could build and install {{Package AUR|lib32-gconf}} if desired, but there is an easier workaround. First, create or edit {{Filename|~/.gtkrc-2.0}} so that it contains the following line:
+
Recent versions of Skype allow you to change the theme via the Options menu. However, selecting the GTK+ option may not work properly. This is probably because you do not have a 32-bit theme engine installed. Try to find the engine your theme uses in the multilib repository or the [[AUR]]. Once installed, it will still not work unless you have a 32-bit version of GConf installed. You could build and install {{Package AUR|lib32-gconf}} if desired, but there is an easier workaround. First, create or edit {{ic|~/.gtkrc-2.0}} so that it contains the following line:
  
 
  $ gtk-theme-name = "My Theme"
 
  $ gtk-theme-name = "My Theme"
Line 275: Line 275:
 
  $ skype
 
  $ skype
  
The GTK+ theme should now appear correctly. You can make this permanent either by running Skype from a script containing the above 2 lines, or by exporting GTK2_RC_FILES in {{Filename|~/.xprofile}} or {{Filename|~/.xinitrc}}, depending on how you start X.
+
The GTK+ theme should now appear correctly. You can make this permanent either by running Skype from a script containing the above 2 lines, or by exporting GTK2_RC_FILES in {{ic|~/.xprofile}} or {{ic|~/.xinitrc}}, depending on how you start X.
  
 
If you cannot change the theme in the Options menu, run Skype using the following command:
 
If you cannot change the theme in the Options menu, run Skype using the following command:
Line 281: Line 281:
 
  $ /usr/bin/skype --disable-cleanlooks -style GTK
 
  $ /usr/bin/skype --disable-cleanlooks -style GTK
  
If you wish menus within desktop environments to load Skype with a GTK theme by default then modify the 'Exec' line of {{Filename|/usr/share/applications/skype.desktop}} so that it reads:
+
If you wish menus within desktop environments to load Skype with a GTK theme by default then modify the 'Exec' line of {{ic|/usr/share/applications/skype.desktop}} so that it reads:
  
 
  $ Exec=/usr/bin/skype --disable-cleanlooks -style GTK
 
  $ Exec=/usr/bin/skype --disable-cleanlooks -style GTK
  
Similarly if you have set Skype to autostart then modify {{Filename|~/.config/autostart/skype.desktop}} in the same way.
+
Similarly if you have set Skype to autostart then modify {{ic|~/.config/autostart/skype.desktop}} in the same way.
  
 
===The microphone does not work===
 
===The microphone does not work===
Line 325: Line 325:
  
 
===Monster/low-octave "growling" distortion over mic===
 
===Monster/low-octave "growling" distortion over mic===
Some users with newer kernels are experiencing a monster-like growling distortion of their sound stream on the other end of Skype. This can be fixed by creating a dummy ALSA device or by removing {{Filename|~/.Skype/shared.xml}}. See https://bbs.archlinux.org/viewtopic.php?pid=819500#p819500 for more information.
+
Some users with newer kernels are experiencing a monster-like growling distortion of their sound stream on the other end of Skype. This can be fixed by creating a dummy ALSA device or by removing {{ic|~/.Skype/shared.xml}}. See https://bbs.archlinux.org/viewtopic.php?pid=819500#p819500 for more information.
  
 
===Skype can only see pulseaudio, but not ALSA devices===
 
===Skype can only see pulseaudio, but not ALSA devices===
Line 335: Line 335:
 
===Crackling / Noisy sound (mainly using 64-bit OS) ===
 
===Crackling / Noisy sound (mainly using 64-bit OS) ===
  
Edit {{Filename|/etc/pulse/default.pa}} and change the following line
+
Edit {{ic|/etc/pulse/default.pa}} and change the following line
  
 
  load-module module-udev-detect
 
  load-module module-udev-detect

Revision as of 10:58, 13 February 2012

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Installing and Running Skype

Template:Package Official is available in [community] for i686 systems and [multilib] for x86_64 systems [1] or as bin32-skype-oss for the OSS sound system in the AUR. Enable the appropriate repository in /etc/pacman.conf and then use pacman to install Skype,

# pacman -S skype

Running Skype is just as easy. Type skype into a terminal or double-click the Skype icon on your desktop or in your DE's application menu.

Securing Skype

There are a couple of reasons you might want to restrict Skype's access to your computer:

  • The skype binary is disguised against decompiling, so nobody is (still) able to reproduce what it really does.
  • It produces encrypted traffic even when you are not actively using Skype.
  • ...

See [2] for more information.

AppArmor

Follow the instructions here to set up AppArmor.

The userland tools for AppArmor come with a collection of example profiles. Skype is amongst them. Copy this to the directory where AppArmor profiles are stored.

# cp -ip /etc/apparmor/profiles/extras/usr.bin.skype /etc/apparmor.d/

For whatever reason, the profile is not complete. You may wish to modify it further. Here is an example. (If the Mozilla denials annoy you, feel free to uncomment the appropriate lines.)

To use the profile, first be sure securityfs is mounted,

# mount -t securityfs securityfs /sys/kernel/security

Load the profile by the command,

# apparmor_parser -r /etc/apparmor.d/usr.bin.skype

Now you can run Skype restricted but as your own user. Denials are logged in messages.log.

TOMOYO

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: please use the first argument of the template to provide a brief explanation. (Discuss in Talk:Skype#)
TOMOYO

Use Skype with special user

Instead of using AppArmor or TOMOYO which require the installation of extra packages, one may prefer to add a special user. This user is only used for running Skype within one's normal environment. This approach restricts Skype to reading only the data of this particular user instead of one's main user. (The new user should not be used for any other thing. Skype only.)

Optionally, we first add a default group for the skype user. I will call the new user and its default group "skype". The security advantage in keeping the "skype" user in its separate group is that it can be restricted from accessing some places other users are allowed in.

# groupadd skype

Then we have to add the new user:

# adduser

Enter the details for the new user (assumed login name: "skype"). If you created the default "skype" group and want to keep "skype" outside the "users" group, enter "skype" when the wizard asks for the initial group. As additional groups we need "audio,video,pulse-access,pulse-rt".

Now add the following line to /home/skype/.bashrc:

export DISPLAY=":0.0"

At last we define the alias (e.g. in ~/.bashrc):

alias skype='xhost +local: && su skype -c skype'

Now we can start Skype as the newly created user simply by running skype from the command line and entering the password of the user skype.

If you are tired of typing in the skype user's password every time, make sure you installed the sudo package, run visudo then add this line at the bottom:

%wheel ALL=(skype) NOPASSWD: /usr/bin/skype

And use this alias to launch skype:

alias skype='xhost +local: && sudo -u skype /usr/bin/skype'

I noticed that the newly created user is able to read some of the files in my home directory because the permissions were a+r, so I changed them manually to a-r u+r and changed umask from 022 to 066.

In order to restrict user "skype" accessing your external drive mounted in /media/data for instance, make sure first that "skype" does not belong to group "users" (if you used the default group "skype", everything should be fine), then change the accesses on the mount point:

# chown :users /media/data
# chmod o-rwx /media/data

This way, it is ensured that only the owner (normally "root") and "users" can access the specified directory tree while the others, including "skype", will be forbidden.

Skype Sound

Skype supports PulseAudio since version 2.1 and ALSA since version 2.0. Earlier versions support only the deprecated OSS.

Skype PulseAudio Sound (2.1+)

Sound should work out of the box, if not you can select another input using pavucontrol (you may have to install it first).

If you are on x86_64 and use the multilib Template:Package Official package, you also need Template:Package Official.

Skype ALSA Sound (2.0+)

Sound should work out of the box, if not you can select a sound device to use in Skype options. If you have problems with Skype blocking your sound device, you only need to add the following to your ~/.asoundrc

pcm.dmixout {
  # Just pass this on to the system dmix
  type plug
  slave {
     pcm "dmix"
  }
}

then you can start Skype as normal, go to the audio options and select dmixout as your speaker- and ringingdevice.

Skype-OSS Sound (Pre-2.0)

If you have a recent version of Skype, this will not work and is not needed, look at the "important notes" on start of this page. Option B is preferred over other options. With option B you can use Skype AND let other programs play sound too. With option C you can do that too, but option B is way easier to set up.

An OSS compatible version is available from here. Then download the PKGBUILD for x86-64 users form here. Correct the md5sum in the PKGBUILD, and also install Template:Package Official (for x86-64 users). Finally, run

$ makepkg -s

to create the pacman installable package.

A. With OSS or Kernel OSS emulation for ALSA

Start Skype and make sure no other program is using your soundcard. If you want to use Skype AND let another program play sound too, look at option B instead.

B. Making ALSA + dMix work for Skype

First of all, we need to install the Template:Package Official package with pacman:

# pacman -S alsa-oss

Add the following to ~/.asoundrc. If the file does not exist yet, just create it! (Many thanks to Lorenzo Colitti for figuring this out!)

# .asoundrc to use skype at the same time as other audio apps like xmms
#
# Successfully tested on an IBM x40 with i810_audio using Linux 2.6.15 and
# Debian unstable with skype 1.2.0.18-API. No sound daemons (asound, esd, etc.)
# running. However, YMMV.
#
# For background, see:
#
# https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1228
# https://bugtrack.alsa-project.org/alsa-bug/view.php?id=1224
#
# (C) 2006-06-03 Lorenzo Colitti - http://www.colitti.com/lorenzo/
# Licensed under the GPLv2 or later

pcm.skype {
   type asym
   playback.pcm "skypeout"
   capture.pcm "skypein"
}

pcm.skypein {
   # Convert from 8-bit unsigned mono (default format set by aoss when
   # /dev/dsp is opened) to 16-bit signed stereo (expected by dsnoop)
   #
   # We cannot just use a "plug" plugin because although the open will
   # succeed, the buffer sizes will be wrong and we will hear no sound at
   # all.
   type route
   slave {
      pcm "skypedsnoop"
      format S16_LE
   }
   ttable {
      0 {0 0.5}
      1 {0 0.5}
   }
}

pcm.skypeout {
   # Just pass this on to the system dmix
   type plug
   slave {
      pcm "dmix"
   }
}

pcm.skypedsnoop {
   type dsnoop
   ipc_key 1133
   slave {
      # "Magic" buffer values to get skype audio to work
      # If these are not set, opening /dev/dsp succeeds but no sound
      # will be heard. According to the ALSA developers this is due
      # to skype abusing the OSS API.
      pcm "hw:0,0"
      period_size 256
      periods 16
      buffer_size 16384
   }
   bindings {
      0 0
   }
}

If you get the error message :

The dmix plugin supports only playback stream

then add the following to .asoundrc:

pcm.asymed {
        type asym
        playback.pcm "dmix"
        capture.pcm "dsnoop"
}

pcm.!default {
        type plug
        slave.pcm "asymed"
}


Now run Skype in this way each time you want to use it:

ALSA_OSS_PCM_DEVICE="skype" aoss skype

Optionally you can make a script to start Skype:

As root, create the file: /usr/bin/askype

# Little script to run Skype correctly using the modified .asoundrc
# See: http://wiki.archlinux.org/index.php/Skype for more information!
#
# Questions/Remarks: profox@debianbox.be

ALSA_OSS_PCM_DEVICE="skype" aoss skype

Now make sure every user is able to execute the file:

# chmod a+x /usr/bin/askype

You can also fix the menu entry so you can start Skype from the your window manager's menu:

Edit the file: /usr/share/applications/skype.desktop

[Desktop Entry]
Name=Skype
Comment=P2P software for high-quality voice communication
Exec=askype
Icon=skype.png
Terminal=0
Type=Application
Encoding=UTF-8
Categories=Network;Application;

Sometimes it takes a while for Skype to start up but once it is loaded it should work ok!

C. Using OSS emulation with oss2jack

Template:Package AUR is another way to have OSS emulation without using ALSA directly. Instead, oss2jack creates a OSS device that forwards everything to JACK (JACK Audio Connection Kit), which in turn mixes, then outputs to the standard ALSA device. For more information on setting this up, please refer to Allow_multiple_programs_to_play_sound_at_once#ALSA_with_oss2jack.

Skype plugin for Pidgin

See Pidgin#Skype plugin.

Problems

Skype crashes immediately

Try creating the directory

~/.Skype/Logs

Skype crashes shortly after login

If Skype crashes shortly after logging in, changing the rights for libpulse.so.0.12.4 (minor version might differ) and libpulse-simple.so.0.0.3 might fix the issue.[3]

# cd /usr/lib
# chmod ugo-r libpulse.so.0.12.*
# chmod ugo-r libpulse-simple.so.0.0.3

64bit users might have to cd to /usr/lib32 instead.

I can receive multiple audio streams, but I can only send one

Skype can send and receive audio and I still hear other sounds playing from other applications, but I cannot record my microphone with other applications. That is because Skype or aoss blocks the audio input for itself.

No video with GSPCA webcams

For i686, install Template:Package Official, userspace tools and conversion library for Video 4 Linux, and run Skype with

LD_PRELOAD=/usr/lib/libv4l/v4l1compat.so skype

to start Skype with v4l1 compatibility.

For x86_64, install Template:Package Official from [multilib] repository and run Skype with

LD_PRELOAD=/usr/lib32/libv4l/v4l1compat.so skype

To make it running from DE menus and independent of Skype updates, you can add alias (e.g. in ~/.bashrc):

alias skype='LD_PRELOAD=/usr/libxx/libv4l/v4l1compat.so skype'

where `libxx' should be edited as appropriate.

No video with Compiz

Try this

$ XLIB_SKIP_ARGB_VISUALS=1 skype

Skype does not use my GTK theme, even though other QT apps do

Recent versions of Skype allow you to change the theme via the Options menu. However, selecting the GTK+ option may not work properly. This is probably because you do not have a 32-bit theme engine installed. Try to find the engine your theme uses in the multilib repository or the AUR. Once installed, it will still not work unless you have a 32-bit version of GConf installed. You could build and install Template:Package AUR if desired, but there is an easier workaround. First, create or edit ~/.gtkrc-2.0 so that it contains the following line:

$ gtk-theme-name = "My Theme"

Replace My Theme by the name of your theme, but leave the quotes. Second, run Skype like this:

$ export GTK2_RC_FILES="/etc/gtk-2.0/gtkrc:$HOME/.gtkrc-2.0"
$ skype

The GTK+ theme should now appear correctly. You can make this permanent either by running Skype from a script containing the above 2 lines, or by exporting GTK2_RC_FILES in ~/.xprofile or ~/.xinitrc, depending on how you start X.

If you cannot change the theme in the Options menu, run Skype using the following command:

$ /usr/bin/skype --disable-cleanlooks -style GTK

If you wish menus within desktop environments to load Skype with a GTK theme by default then modify the 'Exec' line of /usr/share/applications/skype.desktop so that it reads:

$ Exec=/usr/bin/skype --disable-cleanlooks -style GTK

Similarly if you have set Skype to autostart then modify ~/.config/autostart/skype.desktop in the same way.

The microphone does not work

Run amixer,

$ amixer

and check if you have an output for Capture similar to the one below.

Simple mixer control 'Capture',0
 Capabilities: cvolume cswitch penum
 Capture channels: Front Left - Front Right
 Limits: Capture 0 - 15
 Front Left: Capture 8 [53%] [12.00dB] [on]
 Front Right: Capture 8 [53%] [12.00dB] [on]

If your output is similar, your microphone is working just fine, and the issue is either hardware related (broken microphone) or your volume needs to be checked. If you do not have an output similar to the one above or, more specifically, if both Front Left and Front Right are 0% or show an [off] tag at the end, then your microphone settings need to be rectified.

In either case, try to run:

$ alsamixer

and press F5 to show all channels. Using the arrow keys navigate all the way to the end and increase Capture. If you do not see a left and right channel for Capture, press the space bar. Doing this turns the left and right channels on. Check that Input Source is set to the correct value (e.g. [Front Mic]): navigate through the values with up and down arrow keys. If your microphone is an array built into your monitor, or you have a similar setup, make sure to increase the volume for the Digital column too. If you have multiple microphones, you may have to play around with the Mic Jack channel to get your desired setting.

You may want to save your mixer settings with:

# alsactl -f /var/lib/alsa/asound.state store

No incoming video stream

This might be related to Cairo dock, though I am not sure. You need to start skype with:

export XLIB_SKIP_ARGB_VISUALS=1 && skype

Low sound in Skype, but works everywhere else

If you are sure your microphone is configured correct in ALSA (try recording with a 3rd-party-utility to determent whether it is an ALSA, or Skype problem), it is most likely because Skype is controlling your volume levels. Simply disable this feature in the voice settings page in the Skype configuration window.

This may also help if your microphone input is automatically lowered until 0.

Monster/low-octave "growling" distortion over mic

Some users with newer kernels are experiencing a monster-like growling distortion of their sound stream on the other end of Skype. This can be fixed by creating a dummy ALSA device or by removing ~/.Skype/shared.xml. See https://bbs.archlinux.org/viewtopic.php?pid=819500#p819500 for more information.

Skype can only see pulseaudio, but not ALSA devices

Turn PulseAudio autospawn off, normally: $ echo "autospawn = no" > ~/.pulse/client.conf
Kill PulseAudio: $ killall pulseaudio
Shut down and restart Skype

Crackling / Noisy sound (mainly using 64-bit OS)

Edit /etc/pulse/default.pa and change the following line

load-module module-udev-detect

to

load-module module-udev-detect tsched=0

See also: PulseAudio#Glitches.2C_skips_or_crackling.