Getting several applications using the sound card at the same time ?

From Ekiga

1 What can you expect ?
2 What do you need ?
3 How to set up ?
- 3.1 ALSA
- 3.2 Ekiga
4 Troubleshooting
- 4.1 Slackware 11.0
5 Feedback

What can you expect ?

After setting your GNU/Linux system as following, you can listen music or watch a movie and you will heard Ekiga ringing.

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What do you need ?

This documentation will show you how to setup the Advanced Linux Sound Architecture (ALSA) to achieve this goal using the Dmix plugin and the Dsnoop plugin. It provides for direct mixing of multiple audio streams.

ALSA is now shipped with the Linux kernel.

For ALSA 1.0.9rc2 (Linux kernel 2.6.12) and higher you don't need to setup Dmix. Dmix is enabled as default for soundcards which don't support hardware mixing. To get ALSA version: $ cat /proc/asound/version. Even in this cas, following the instructions below will help tuning it or you can try configure Ekiga to use the "Default" of ALSA -which should use Dmix- as explained in the next chapter How to set up ? -> Ekiga.

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How to set up ?

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ALSA

ALSA use now Dmix by default.

Be sure all the audio aplications are using ALSA as a sound system and "Default" as device.

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Ekiga

Now you have to setup Ekiga acordingly.

Go to the menu Edition → Preferences → Audio Devices

Select "Default (PTLIB/ALSA)" as ringing device
Select "Default (PTLIB/ALSA)" as output
Select "Default (PTLIB/ALSA)" as input

The "Default" will use the configuration provided by your .asoundrc

That's all. Enjoy.

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Troubleshooting

Does your ALSA fits Ekiga needs ?

You can test your actual ALSA configuration using those echo tests:

 $ arecord -D plughw:0,0 -c 1 -r 8000 -f S16_LE - | aplay -D plughw:0,0 -c 1 -r 8000 -f S16_LE -

This one test if your sound card can record and play sounds at 8kHz.

 $ arecord -D plughw:0,0 -c 1 -r 16000 -f S16_LE - | aplay -D plughw:0,0 -c 1 -r 16000 -f S16_LE -

This one test if your sound card can record and play sounds at 16kHz.

You should be able to hear yourself with a small delay. Be sure to have your sound levels up and capture on.

DMIX crashes Ekiga

ALSA version 1.0.11 bug: DMIX crashes Ekiga. To check your version : $ cat /proc/asound/version.

Downgrade to 1.0.10, or upgrade to 1.0.12

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Slackware 11.0

Slackware 11.0 use ALSA 1.0.11: Upgrade ALSA to 1.0.12 at least.

Choppy sound with Ekiga

From ALSA version 1.0.9, DMIX is enabled by default for soundcards that do not support several channels at the same time. The default configuration of DMIX in ALSA does not necessarily provide good results by default for VoIP applications. The solution is to directly use the soundcard preferences in the 'Audio Settings' or to redefine your "default" soundcard as described above.

Choppy sound when switching desktops or under heavy load

Nothing can be done. We suggest not using DMIX if you experience that problem. If you do not use the 'Default' soundcard in the Audio Settings, then DMIX will not be used.

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