This section answers some frequently asked questions about aRts.
KDE uses aRts to play sound, and aRts uses the Linux® kernel sound drivers, either OSS or ALSA (using OSS emulation). If your sound card is supported by either ALSA or OSS and properly configured (i.e. any other Linux® application can output sound), it will work. There are however some problems with some specific hardware, please read the section for hardware specific problems if you're having problems with artsd on your machine.
Meanwhile also support for various other platforms has been added. Here is a complete list of how the most recent version of aRts can play sound. If you have an unsupported platform, please consider porting aRts to your platform.
|aRts audio I/O method||Comment|
|paud||Support for AIX Personal Audio Device|
|alsa||Linux ALSA-0.5 and ALSA-0.9 drivers|
|libaudioio||Support for generic LibAudioIO library which works on Solaris|
|nas||NAS sound server, useful for X Terminals with NAS support|
|null||Null audio device, discards sound silently|
|oss||OSS (Open Sound System) support (works on Linux, various BSDs and other platforms with OSS drivers installed)|
|toss||Threaded OSS support, which works better in some cases where the standard OSS support doesn't work well|
|sgi||SGI Direct Media support for IRIX|
You can achieve the same effect in a terminal window using the command chmod 666 /dev/dsp.
For restricting access to sound to specific users, you can use group permissions. On some Linux® distributions, for instance Debian/Potato, /dev/dsp is already owned by a group called audio, so all you need to do is add the users to this group.
There are various other devices which provide functionality accessed by multimedia applications. You can treat them in the same way, either by making them accessible for everyone, or using groups to control access. Here is a list, which may still be incomplete (also if there are various devices in a form like midi0, midi1, ..., then only the 0-version is listed here):
First of all: try using the default settings in KControl (or if you are starting manually, don't give additional options besides maybe -F10 -S4096 for latency). Especially full duplex is likely to break with various drivers, so try disabling it.
A good way to figure out why artsd doesn't start (or crashes while running) is to start it manually. Open a Konsole window, and do:
% artsd -F10 -S4096>
You can also add the -l0 option, which will print more information about what is happening, like this:
% artsd -l0 -F10 -S4096
Doing so, you will probably get some useful information why it didn't start. Or, if it crashes when doing this-and-that, you can do this-and-that, and see “how” it crashes. If you want to report a bug, producing a backtrace with gdb and/or an strace may help finding the problem.
You can't relocate aRts perfectly. The problem is that artswrapper has the location of artsd compiled in due to security reasons. You can however use the .mcoprc file (TraderPath/ExtensionPath entries) to at least make a relocated artsd find it's components. See the chapter about the .mcoprc file for details on how to do this.
Long answer: In the official release, there are two gcc-3.0 bugs which affect aRts. The first, gcc-3.0 bug c++/2733 is relatively harmless (and has to do with problems with the asm statement). It breaks compilation of convert.cc. It has been fixed in the gcc-3.0 CVS, and will no longer be a problem with gcc-3.0.1 and higher. A workaround has also been added to the CVS version of KDE/aRts.
The second gcc-3.0 bug, c++/3145 (which is generation of wrong code for some cases of multiple virtual inheritance) is critical. Applications like artsd will simply crash on startup when compiled with gcc-3.0. Even if some progress has been made in the gcc-3.0 branch at time of this writing, still artsd crashes quite often, unpredictably.
Some KDE applications that are not yet included in the KDE release (e.g. in kdenonbeta) also support aRts, including:
The following non-KDE applications are known to work with aRts:
The following applications are known not to work with aRts:
See also the answers to the questions in the section on non-aRts applications.
This section is incomplete -- if you have more information on supported and unsupported applications, please send them to the author so they can be included here.
If you start artsd from the KDE control panel, the default is to suspend after 60 seconds. If you start artsd from the command line you need to use the -s option to specify the autosuspend time, otherwise it will default to disabling the autosuspend feature.
Currently it doesn't suspend when using full duplex. Turn full duplex off from the KControl and it will suspend. Disabling full duplex is generally a good idea anyway if you only use aRts for playing audio and not recording.
% mpg123 foo.mp3
% artsdsp mpg123 foo.mp3
This will redirect the sound output to aRts. This method doesn't require changes to the applications. It is something of an ugly hack however, and does not yet fully support all features of the sound card device, so some applications may not work.
No. Using artsdsp can result in slightly more latency and CPU usage that using the aRts APIs directly. Other than that, any application that doesn't work should be considered a bug in artsdsp. The technique used by artsdsp should, if implemented properly, allow every application to work with it (including large applications like Quake 3).
You can wait for artsd to suspend or use the command artsshell suspend to ask the server to suspend itself. You will only be able to suspend the server if no aRts applications are currently using it, and no aRts applications will be able to run when the server is suspended.
If the server is busy, a crude but effective way to get rid of it is:
% killall artsd ; killall artswrapper Now start your own application. % kcminit arts
Any currently running aRts applications may crash, however, once you kill the server.
If you are running KDE 1.x applications, which output sound via the KDE 1 audio server, you will need to run kaudioserver to make it work. You can start kaudioserver in the same way than other non-aRts-applications:
% artsdsp kaudioserver
You will need to have installed kaudioserver (from the same source where you got your KDE 1.x applications from) - it belongs to KDE 1.x, not KDE 2.
This is most likely not a bug, but caused by the fact that the Linux® kernel is not very good at real-time scheduling. There are situations where aRts will not be able to keep up with playback. You can, however, enable real-time rights (via KControl), and use a large latency setting (like 250ms or don't care), which should improve the situation.
The help text for this setting in the KControl can be misleading. A lower value means that aRts will take less time to respond to external events (i.e.. the time that it takes between closing a window and hearing a sound played by artsd). It will also use more CPU resources, and be more likely to cause dropouts.
For users of IDE drives, you can use the hdparm command to put your IDE drive in DMA mode. A word of warning: this does not work on all hardware, and can result in having to do a hard reset or in rare cases, data loss. Read the documentation for the hdparm command for more details. I have successfully used the following command:
% hdparm -c1 -d1 -k1 -K1 /dev/hda
You need to run this after every boot, so you might want to place it in a system startup script (how to do this distribution specific, on Debian Linux® it is usually put in /etc/rc.boot).
Verify that artswrapper is really installed suid root, like it is supposed to be. A lot of distributions (SuSE7.x for instance) don't do this. You can verify this using: ls -l $(which artswrapper). Good:
% ls -l $(which artswrapper) -rwsr-xr-x 1 root root 4556 Sep 24 18:05 /opt/kde2/bin/artswrapperBad:
% ls -l $(which artswrapper) -rwxr-xr-x 1 root root 4556 Sep 24 18:05 /opt/kde2/bin/artswrapperIf you are not having the s, you can get it using:
% chown root $(which artswrapper) % chmod 4755 $(which artswrapper)
Enable it in the KControl Sound Server settings (enable X11 server for security information and network transparency). Then copy your .mcoprc to all machines you plan to use network transparency from. Log in again. Make sure that the hosts that interact know each other by name (i.e. they have resolvable names or are in /etc/hosts).
This should be all you need to do. However, if it still doesn't work here are some additional details. The aRts sound server process, artsd, should only run on one host, the one with the sound card where the sound should be played. It can be started automatically on login by KDE (if you configure that in KControl), or manually using something like:
% artsd -n -F 5 -S 8192
The -n parameter is for network transparency, while the others configure latency.
Your .mcoprc file should have this entry:
on all machines involved, in order for network transparency to work, This is what is enabled by the X11 server for security information control panel setting.
Finally, in any KDE version in the 2.0.x series, there is a bug which applies if you don't have a domain name set. Clients of artsd try to find where to connect to via the hostname.domainname combination. If your domain name is empty, it will try to connect to hostname. (note the extra dot). Adding an entry like this to /etc/hosts (i.e. orion. if your hostname is orion) works around the problem.
% ./referenceinfo global:Arts_SimpleSoundServer
The output will indicate the host name and port being used by aRts. For example, tcp:orion:1698 would mean that any client trying to use network transparency should know how to reach host orion.
It seems that there are a few linux drivers which don't work well with aRts in some kernel versions. Please read this list before reporting a bug. If you find that some information in this list is incomplete, please don't hesitate to let us know.
|Linux Driver / Soundcard||Fails under||Works under||Remarks|
|i810 driver (Intel 810 + AC97 Audio)||2.4.9||2.4.18, 2.2.20, commercial oss driver, alsa-0.5.12a with OSS emulation||driver causes cpu overload (see below)|
|maestro 3/4 chipset||2.4.9||?||driver sometimes causes cpu overload (see below)|
|aureal8820, aureal8830 drivers from sourceforge||2.4.17||?||driver triggers assertion / causes cpu overload (see below)|
|OSS Commercial 3.9.4g with Aureal Vortex||?||?||system lockup|
|ymfpci||2.4.0, 2.4.12||2.4.17||driver triggers assertion (see below)|
You might notice that some other applications (like xmms) may not need this data, and thus work correctly even with your hardware. However, aRts needs this data, so artsd might fail. This is still a bug in the driver, and not in aRts.
There are two kinds of behaviour that artsd exposes on being run on an incorrect driver. Either, it continously tries to feed new data, but never really succeeds, which eventually leads to consuming all CPU power and reporting cpu overload and exiting. The other problem is that artsd might get supplied with wrong information how much to write. Artsd will then stop with an assertion like:
artsd: audiosubsys.cc:458: void Arts::AudioSubSystem::handleIO(int): Assertion `len == can_write' failed. Aborted
A problem occurs if artsd is woken up either always or if there are minimal amounts of data to write. The OSS documentation specifies that select() only wakes up a process if there is at least one fragment to write. However, if artsd is woken up if there isn't data to write, or very little, for instance one sample, then it will keep writing little pieces of audio data, which can be very costly, and eventually overload the cpu.
To fix this, the driver should wake up artsd only if there is a full fragment to write.
If artsd can't write as much data as indicated by the ioctl, it will fail in the assertion. To fix this, the driver should supply the correct amount of free space.
The most likely cause is that you are using old structures or modules which aren't supported with the KDE 2 version. Unfortunately the documentation which is on the web refers to aRts-0.3.4.1 which is quite outdated. The most often reported crash is: that performing an execute structure in aRts-builder results in the error message [artsd] Synth_PLAY: audio subsystem is already used.
You should use a Synth_AMAN_PLAY instead of a Synth_PLAY module and the problem will go away. Also see the aRts-builder help file (hit F1 in aRts-builder).
Recent versions of aRts-builder (KDE 2.1 beta 1 and later) come with a set of examples which you can use.