Frequently Asked Questions by KDE Multimedia Users

This is not a question, but is common. It is possible for aRts to interact with many decoders if someone chooses to create an aRts plugin for it. Ewald Snel did it for Xine, so supporters of other players can follow his lead.

For KDE 4 aRts support will be discontinued and KDE will be able to use any other media framework like GStreamer, NMM, libxine or Helix DNA Client. For more information have a look at the Phonon Website.

Non-aRts Applications

As soon as KDE is running, no other application can access my sound device?

Yes, since the aRts sound server KDE uses is running, it is using the sound device. If it is idle for 60 seconds, it will release it automatically (auto-suspend).

You said it suspends after 60 seconds, it doesn't for me?

In previous versions aRts didn't suspend when using full duplex. Upgrade to a newer version or turn off full duplex and it will suspend. Turning it off is a good idea anyway if you only use aRts for playing things.

What should I do to run non-aRts applications?

Start them with artsdsp. For instance, if you normally would run mpg123 foo.mp3 use artsdsp mpg123 foo.mp3 now. This will redirect the sound output to aRts. As you see this method doesn't require changing existing apps. It is a bit hacky however, and does not yet fully support all features of the soundcard right now, so some apps might not work.

Are there theoretical limits which apps will never work with artsdsp?

No. Of course artsdsp will have a little more latency and a little more CPU usage. Other than that, consider every app that doesn't work with artsdsp a bug in artsdsp. Basically the way artsdsp works should, if implemented properly, make EVERY app work with it (including stuff like quake3).

What do I do if an app doesn't work with artsdsp?

To pause the sound server, open up the aRts Control Tool (artscontrol). If you View aRts Status in that application, you will be offered a button to suspend aRts use of the sound server.

Latency

I sometimes get short pauses when listening to music, is this a bug?

This is not a bug in aRts, but a side-effect of its design. aRts attempts to work in a real-time manner (hence the capital R), and the large buffering that some media players does is not always possible. So for maximum playback reliability, take these steps:

• Configure in KControl your aRts server to use realtime priority and a reasonable buffering level. (Note that for realtime priority to be accessible, the artswrapper binary will probably need setuid root permissions, in order to give the non-root artsd the realtime scheduling).
• Make sure your OS's kernel has been configured to minimize latency issues. Linux 2.6 users can use the "preemption" option in their kernel. Linux 2.4 users can apply a patch to add a preemption option to their kernel. Please mail kde-multimedia@kde.org if you know how to optimally configure a kernel not listed here.

Whats the effect of the response time setting anyway?

A lower value means that aRts will take less time to respond to external events (i.e. time time that it takes between closing a window and hearing a sound played by artsd), will use more cpu, and more likely cause dropouts.

Why is artsd taking that much CPU time?

Check your response time settings. On the other hand, the KDE2.0 version is not yet really optimized. This will improve, and until then no real prediction can be made how fast artsd can or can't be.

Network Transparency

What do I need for network transparency?

Enable it in kcontrol (enable X11 server for security information and network transparency). Then go and copy your .mcoprc to all machines you plan to use network transparency from. Relogin. Make sure that the hosts that interact know each other by name (i.e. make sure that they have resolvable names or are in /etc/hosts).

Can I debug it if it doesn't work?

Yes, if you have the source. go to arts/examples, make check there, then run referenceinfo global:Arts_SimpleSoundServer there you'll see what hostname and port aRts. For instance tcp:orion:1698 would mean that any client trying to use artsd network transparent should know how to reach "orion".