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Dmix Kde - arts, ESD and SDL quick and dirty HOWTO

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The information on this page is out of date but still of some interest when dealing with the subject matter.

Contents

2004-09-02

The version of KDE available in Debian "Sid" Unstable includes artsd 1.3.0. It can be used with asound to produce sound even while other applications are playing, using a configuration like the ones at the bottom of this page.

pcm.card0 {
    type hw
    card 0
}
pcm.!default {
    type plug
    slave.pcm "dmixer"
}
pcm.dmixer  {
    type dmix
    ipc_key 1025
    slave {
        pcm "hw:0,0"
        period_time 0
        period_size 4096
        buffer_size 16384 
        periods 128
        rate 44100
    }
    bindings {
        0 0
        1 1
    }
}


[esd]
auto_spawn=1
spawn_options=-terminate -nobeeps -as 2 -d default  # <====
spawn_wait_ms=100

If you notice that esd doesn't want to play through default device, or if you launch esd -d default, it segfaults, it means that you have esound \<= 0.2.32, which use obsolete alsa API. If it's true, install more recent, or compile latest esound with esound-alsa-pcm-newapi.patch http://cvs.pld-linux.org/SOURCES/esound-alsa-pcm-newapi.patch)

\

export AUDIODEV=default

... and problems disappeared? unfortunately not :[[. Some application behaves strange when AUDIODEV is set. For example: mozilla crashed when you touch the keyboard, and scorched3d runs few times slower. Strange, but true. So if you notice such problem, you must manually set AUDIODEV for your applications, instead of globally set it in /etc/profile.d/dmix_sdl.sh

(Note: see comment below by Stefan Briesenick for a better solution to this problem)

Other known problems

Additional comment by Alexander E. Patrakov

The proposed wrapper-based solution of the artsd problem does not work for me with KDE 3.2.0 and FM801-based soundcard. Artsd plays for several seconds and then hangs. I managed to solve the problem by just selecting esd as the output device for artsd.

Additional comment by Manfred Vogelgesang

Regarding the claim that the periodsize MUST be 4096 (or artsd would reject it otherwise) I found out that it DOES work for my previous value of 1024! This periodsize of 1024 in my .asoundrc works when artsd is launched with "-S 1024", like for instance:

aoss /opt/kde3/bin/artsd -S 1024 -a toss -r 48000 &

Unfortunately, preloading "aoss" doesn't seem to work with "artswrapper"; it appears that you must call "artsd" directly. Moreover, mplayer complains about the period size when it is set at 4096, while it works with 1024, for instance when calling it like:

mplayer -srate 48000 -ao alsa9:pcm.dmixer

This command worked for me, I really got mplayer to use alsa and allow for mixing sounds (based upon the above .asoundrc and the already mentioned periodsize of 1024 instead of 4096).

After trying this alsa/artsd mixing for some time now, I must conclude: This "solution" doesn't appear to be stable! More often than not, artsd shuts itself down after a more or less brief time! Furthermore, when using this "solution" latency for applications run via artsdsp, e.g. artsdsp -m quake2, increases to a degree that is no longer acceptable - in games like quake2 the latency is especially annoying, while in my experience it is no problem whatsoever, when using artsdsp -m quake2 exclusively, i.e. without mixing artsd with alsa! If someone has ideas to improve the situation, feel free to comment...

Additional comment by Stefan Briesenick

SDL works for me like a charm just with the following environment variable:

SDL_AUDIODRIVER="alsa"

It seems to me, that SDL uses 'default' then as the AUDIODEV by default (so you have to setup 'pcm.!default'), at least mixing is done properly through dmix. Since you don't have to set the AUDIODEV variable, you don't have the mentioned problems above with Mozilla & friends.

Another example

This page seems to be the only resource that describes dmix in combination with arts and esound, so I will tell my experiences here. I have a NForce2 board using the intel8x0 driver under Linux 2.6.5, KDE 3.2.1 and arts 1.2.2. My /etc/asound.conf file is the following:

pcm.ossmix {
    type dmix
    ipc_key 1027       # must be unique!
    slave {
        pcm "hw:0,0"   # you cannot use a "plug"
                       # device here, darn.
        period_time 0
    period_size 1024
    buffer_size 4096
        #format "S32_LE"
        #periods 128   # dito.
        rate 44100     # with rate 8000 you *will* 
                       # hear, if ossmix is used :)
    }
    bindings {
        0 0            # from 0 => to 0
        1 1            # from 1 => to 1
    }
}
pcm.!default {
    type plug
    slave.pcm "ossmix"
}
# mixer0 like above
ctl.mixer0 {
    type hw
    card 0
}

My /etc/esd/esd.conf:

[esd]
auto_spawn=1
spawn_options=-terminate -nobeeps -as 2 -d default
spawn_wait_ms=100

Arts is configured to use ALSA and full duplex is disabled (with enabling full duplex it complains that it cannot open the device for recording). The sampling rate is set to 44100 Hz. I have experimented a long time with the values of period_size and buffer_size. With the "rate" entry was commented out, artsd output was snatchy at period_size 4096 while esound ouput was ok, and at period_size 1024 esound produced unacceptable results while arts was fine. The rate entry fixed this, and now I can use native ALSA, ALSA-OSS, Artsd and EsounD at the same time!

Yet another example

Well, I've been stumbling around with ALSA, and since this wiki helped me, I figured I'd take the time to help back. I'm running an ASUS A7N266-VM motherboard with an nForce chipset -- not even an nForce2. I just wanted KDE to be noise-enabled while I played games and such. Since I'm running Debian unstable, at this date I've got artsd 1.3.0. Although this version of artsd has an ALSA output selection, enabling it didn't help. I'd still hear the test sound, but other sounds queued up with "aplay KDE_Notify.wav &" waited until artsd gave up the device. The solution was to change the device name in my /etc/asound.conf and set artsd to use that device in the Control Center. Using "default" and "dsp0" as the device name produced choppy or blocking sound!

Here's my current asound.conf:

pcm.!default
{
    type plug
    slave.pcm "nmixer"
}
pcm.nforce
{
    type plug
    slave.pcm "nmixer"
}
pcm.dsp0
{
    type plug
    slave.pcm "nmixer"
}

# A bit more control over the mixer
pcm.nmixer
{
    type dmix
    ipc_key 6789  # Any unique number
    slave {
        pcm "hw:0,0"
        period_time 0
        period_size 1024
        buffer_size 4096
        #periods 128
        #rate 44100
     }
    #bindings {
    #    0 0
    #    1 1
    #}
}
ctl.mixer0
{
    type hw
    card 0
}

Another hint

Well, I am using KDE 3.5.2, arts 1.5.2. I have a i810 sound card. After much tinkering I found this worked for me: In KDE Sound Server Configuration, use ALSA as audio device. Then override device location to 'plug:dmix'. Also the tip on setting the rate was very useful to get proper playback. (Check the Use custom sampling rate option and set it the value to 44100 Hz).

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