Listed here are answers to some commonly asked questions and solutions to common problems related to multimedia hardware and software:
Why doesn't my distribution include an MP3 encoder or DVD player?
Due to legal issues related to patents, many Linux distributions do not ship an MP3 encoder or DVD player application. You may be able to download these separately after determining for yourself that they can be used legally in your jurisdication.
Are there free alternatives to MP3 and DVD that are not encumbered by patents?
The Ogg project by the Xiph.org Foundation has developed several encoding formats and free implementations that are free of patent issues including Ogg Vorbis for audio and Ogg Theoris for video. See http://www.xiph.org for more information.
Kernel modules not loaded
This could be caused by incorrect module configuration files. It will also occur if the kernel module loader (kerneld or kmod) is not running. Make sure the module is available for loading in the appropriate directory (typically something like /lib/modules/2.4.17/kernel/drivers/sound).
Sound card not detected
You are probably using the wrong kernel driver or the wrong settings for I/O address, IRQ, or DMA channel.
IRQ/DMA timeout or device conflicts
You are using the wrong settings for I/O address, IRQ, and DMA, or you have a conflict with another card that is using the same settings.
No sound after rebooting
If sound was working and then stopped when the system was rebooted, you probably have a problem with the module configuration files. This can also occur if the system init scripts are not configured to initialize PnP cards or to load the modules. If the drivers are loaded, it could be that the mixer settings are set too low to hear any audio. Use a mixer program to adjust the sound levels while using a media player program to play a known good sound file.
If you are running KDE or GNOME, make sure that the appropriate sound server (aRts or esd) is running. On some systems, you may need to adjust the sound server settings using the control panel provided for this purpose. In the case of KDE you can also conveniently test the sound server from the control panel.
Sound works only for root
This probably indicates a permissions problem with the device files. Many systems allow only users who are members of the group "audio" to access the sound devices. Add the user(s) to this group or change the permissions on the audio devices using the chmod command. Some versions of the 2.6 Linux kernel do not respect the group file permissions for device files, and they need to be made readable to the user who is logged on.
No sound is heard but there are no error messages
If sound programs appear to be playing but nothing is heard, it is probably a problem with the mixer settings, or a problem with the connection of the speakers.
Unable to record audio
This could indicate a problem with the mixer settings. You need to set the levels and select the input device. You might also have a bad microphone or be using the wrong input jack on the sound card.
Device busy error
Either you have a device conflict, or another application is using the sound devices. This could be because you are running a sound server program, such as esd or artsd.
No sound when playing audio CD
To play audio CDs, you need a cable from the CD-ROM drive to your sound card. Make sure you have selected CD input using a mixer program. Try connecting headphones to the front-panel jack of the CD-ROM drive. If you can hear audio, the problem is not with the drive itself. If you can't hear audio from the headphones, the problem is with the drive or CD player program. (Note that some newer CD player programs support digital playback without a cable, but you may need to configure them to operate in this mode.)
Cannot play MIDI files
Some MIDI applications work only with a sound card that has an FM synthesizer, and not all cards have this hardware (or the kernel driver for the sound card may not support it). Try using another MIDI application that supports using the standard audio device.
