Problemas de Som

Entendendo como funciona o som

Para entender como funciona o som no KDE, você deve entender o funcionamento do som no Linux (este capítulo considera que você está rodando seu KDE no Linux). Existem dois tipos de sistemas de som que rodam no Linux: ALSA e OSS. Ambos fornecem seus próprios drivers para as placas de som. O ALSA somente roda no Linux, o OSS roda em vários sistemas UNIX. O ALSA permite que vários aplicativos acessem a placa de som ao mesmo tempo, enquanto o OSS não. O OSS fornece um dispositivo para saída de som. Este dispositivo pode ser acessado somente por uma aplicação de cada vez. Para diminuir a confusão, o ALSA emula o OSS e também fornece um dispositivo como interface para a placa de som. Tanto o ALSA como o OSS chamam o dispositivo de placa de som como /dev/dsp normalmente. O PulseAudio, em algumas distribuições, fornece outra camada acima destes sistemas. É seu trabalho manipular vários fluxos de áudio, de modo que, por exemplo, você possa receber uma notificação de mensagem ao mesmo tempo que está ouvindo música.

Usual sound problems are

• You cannot play sound because you are using an application that tries to access the sound device /dev/dsp, but this device is already in use by another application.
• You cannot use the system-wide mixer kmix to adjust the volume of an application using the sound device /dev/dsp.
• Different applications play sound using different devices.

Solutions: There is no silver bullet solving all your sound problems. The solution depends on the application you use to play sound. As an example, you can use mplayer with ALSA and OSS. For more info, see mplayer's documentation by calling

mplayer -ao help

Here are some specific issues that you may meet.

KDE 4 uses the wrong sound device.

That is not an error, but a configuration issue. To tell KDE 4 which soundcard to use (or prefer if available), open System Settings and go to Multimedia in the General tab.

Devices from /etc/asound.conf or ~/.asoundrc are not listed.

Phonon uses a function introduced in ALSA 1.0.14 to find those devices. To make this function list your entry you need to add a name hint. E.g.

hint {
     show on
     description "Name to display for the device"
 }

Here is a complete example that adds a new volume control named Phonon to your mixer:

pcm.softvolPhonon {
     type softvol
     slave.pcm "default:CARD=0"
     control {
         name "Phonon"
         card 0
     }
     min_dB -51.0
     max_dB 0.0
     resolution 100
     hint {
         show on
         description "My Soundcard with extra Volume Control"
     }
 }

After an update, PulseAudio gives you very low volume

PulseAudio has a 'normaliser' function which can cause this. To turn it off, set flat-volumes = no in /etc/pulse/daemon.conf

You are using KDE 3 and you keep losing sound. Sometimes it works, sometimes it doesn't.

KDE 3.x uses the aRts sound system. In earlier versions there were a number of problems, but in recent years the only problem remaining seems to be that aRts hangs on to the sound system when it has finished with it. To cure this, use kcontrol -> Sound & Multimedia. Towards the bottom of the General tab there is a setting for Auto-suspend if idle after: Set this to 1 second.

You have multimedia keys but KDE doesn't recognise them

This link has a clear description of what one user did to make his Volume-up and Volume-down keys work.

You tried all of the above but it still doesn't work (Ubuntu variants only)

Try replacing your sound card. If you still don't hear sound, check out this Ubuntu Community page