Difference between revisions of "Tips And Tricks"

Revision as of 11:20, 17 July 2009

Starting ossxmix minimized to tray on desktop startup

The '-b' option starts ossxmix in the background - minimized to tray if tray support is compiled in, iconfied window if not. The '-S' option prevents ossxmix from trying to use a system tray. ossxmix -Sb' will always start an iconified window.

1. KDE: create a desktop shortcut in ~/.kde/Autostart with the command 'ossxmix -b'.

   Alternative: create a desktop shortcut in the same place, with the command "ossxmix -Sb'. Go to Applications->"Advanced options" and select "Place in system tray".

2. Gnome: go to "Control center"->"Session"->"Startup Programs" and add "ossxmix -b".

   Note that the quoted names can be slightly different on some systems due to localizations.

3. X11 in general: edit the Xsession file. Make sure the tray program runs before ossxmix, or use the '-S' switch as well.
4. See [1] for info on other environments.

Changing the default sound output

1. • The typical method is to relink /dev/dsp to the desired /dev/oss/.../ device. e.g.

   sudo ln -sf /dev/oss/oss_sbxfi0/pcm0 /dev/dsp

   The device node matching the desired sound output can be discovered by running 'osstest' (and seeing which node produces the desired output) or by examining 'ossinfo -a' (displays list of nodes).

   • Modern OSs put /dev on a ramdisk (i.e. it gets erased in boot), so we need to the new correct setting remains. OSSv4.2 and above stores /dev/dsp setting in $OSSLIBDIR/etc/legacy_devices, so these should be saved automatically as long as OSS is shut down properly (You can run "sudo ossdevlinks" to save this manually).

   OSSv4 before version 4.2, requires editing the $OSSLIBDIR/soundon.user file and readding the relinking command there. You will have to give the soundon.user file executable permissions using "sudo chmod +x" command. If the file doesn't exist, you may create it.

   • In OSS 4.1 and above, it's best to also add a "vmixctl attach" command to the soundon.user file to make sure vmix is attached to the new device and to add "vmix_no_autoattach=1" to the $OSSLIBDIR/conf/osscore.conf file. "vmixctl attach" syntax looks like this:

   vmixctl attach /dev/oss/oss_sbxfi0/pcm0 /dev/oss/oss_sbxfi0/pcmin0

   The second and third argument represent output and input nodes for vmix to attach to, allowing full duplex when /dev/dsp is used. However, the third argument can be omitted in some cases. See "vmixctl" manpage for explanation.

2. Alternative: If the default output is set to an onboard soundcard and you're using another card, you can just disable onboard audio in the BIOS, and it won't be seen by OSS.
3. Alternative: $OSSLIBDIR/etc/installed_drivers influences the order of sound cards set by ossdetect. By removing other devices or moving the desired sound card to the first place, the default device can be modified.

   The root directory $OSSLIBDIR can be found by checking /etc/oss.conf. It is almost always /usr/lib/oss/.

Recording sound output of a program

There are several methods to achieve this:

1. Many drivers offer a 'vol' mixer control. If this can be used as a recording source, than the current sound output will be recorded. Note that this is the mixed total of all sound played, not of a single program.

   ossrecord -ivol blah.wav

   • Some drivers have a 'loopback' mixer control, which offers similar functionality.
2. (This method doesn't work in OSS4.0 build 1016) vmix loopback driver can record the mixed output of sound played. Set vmix1_numloops to 1 (or more) in vmix.conf, and restart OSS. Then record from the newly created loopback device. Note that this is the mixed total of all sound played via vmix, not of a single program.

   ossrecord -s48000 -b16 -c2 -d/dev/oss/oss_ich0/loop0 test.wav

3. OSS wrappers can be used to record the output of a program. vsound is one such wrapper. (vsound doesn't handle output to /dev/oss/* device nodes, but all OSS-supporting programs are/can be easily made to output to /dev/dsp).

   vsound ossplay test.wav

4. oss_userdev or oss_audioloop can also be used to record the output of a single program. Both the recorder and player will need to use the new node created by these drivers, and the recorder has to explicitly set up the appropriate format. In the case of oss_userdev, the recorder has to be run using a udserver, the example one in tutorials/sndkit/udserver should do.

Running a command immediately after OSS is loaded

This can be done using this procedure:

1. Edit the $OSSLIBDIR/soundon.user file and add that command.
2. Make sure that soundon.user has the executable bit set (it is not set by default).

One possible use of this is to have some volume controls set to a fixed level after OSS is started, regardless of their previous level last time OSS was run (by default, OSS restores the previous volume for all controls).

Using multimedia keys with OSS

1. First, we should check if the keys are recongnized by X11 or some other program. Run xev, and see if pressing the keys elicits a response.
   • If it does not, than we must make the keys be recognized by X11/WM/etc., before they can be used for anything. This is outside the scope of this wiki, but is documented at [2] and at [3]. Some WMs, once set up, will automatically connect the multimedia keys to appropriate functions.
2. If/once the keys are recognized, does it work out of the box?
   • If not, it may be a function of old gstreamer version. Gnome uses gstremaer for this, but older gstreamer didn't support OSSv4. See Configuring_Applications_for_OSSv4#Gnome_Volume_Applet for a possible solution.
   • If the above does not work or is not applicable, we can connect the keys to external scripts which will perform the appropriate function (See examples below). The method to connect external scripts to keys is better described at [4] and at [5] again.
     • For example in KDE, you can start the "Control Center", enter "Regional & Accessibility" -> "Input Actions", click on "New Action" and make its type "Keyboard Shortcut -> Command/URL", and then set the multimedia key to launch the script. (Names can be different due to localizations).

External scripts which can control volume

mute.sh

#!/bin/sh
CTRL=vmix0-outvol
touch $HOME/.volume
VOLUME=$(cat $HOME/.volume)
CURRENT=$(ossmix | grep $CTRL | awk '{print $4}' | awk -F : '{print $1}')
if [ $CURRENT = "0.0" ]; then
      ossmix $CTRL $VOLUME
      > $HOME/.volume
else
      VOLUME=$(ossmix | grep $CTRL | awk '{print $4}' | awk -F : '{print $1}')
      ossmix $CTRL 0
      echo $VOLUME > $HOME/.volume
fi

ossvol

If you want the ability to mute and then unmute/increase volume at the same time the following script is one option. (This script relies on OSSv4.1 functionality - see note on ossmix below).

ossvol:

#!/bin/bash
#
# ossvol is a simple script to manage oss volume levels and muting.
#
# Script by: Daniel J Griffiths <ghost1227@archlinux.us>
# Configure stuff
VOLSTORE=~/.volume
CHANNEL="vmix0-outvol"
ARGUMENT=$2
# You shouldn't have to edit below here.
err() {
   echo "$1"
   exit 1
}
usage() {
   echo "usage: ossvol [option] [argument]"
   echo
   echo "Options:"
   echo "     -i, --increase - increase volume by [argument]"
   echo "     -d, --decrease - decrease volume by [argument]"
   echo "     -t, --toggle   - toggle mute on and off"
   echo "     -h, --help     - display this"
   exit
}
toggle() {
   if [ -f $VOLSTORE ]; then
       ossmix $CHANNEL `cat $VOLSTORE`
       rm $VOLSTORE
   else
       VOLUME=$(ossmix $CHANNEL | awk '{print $10}' | awk -F : '{print $1}')
       ossmix $CHANNEL 0
       echo $VOLUME > $VOLSTORE
   fi
}
increase() {
   if [ -f $VOLSTORE ]; then
       TMPVOL=`cat $VOLSTORE`
       NEWVOL=`expr $TMPVOL + $ARGUMENT`
       ossmix $CHANNEL +$NEWVOL
       rm $VOLSTORE
   else
       ossmix $CHANNEL +$ARGUMENT
   fi
}
decrease() {
   if [ -f $VOLSTORE ]; then
       TMPVOL=`cat $VOLSTORE`
       NEWVOL=`expr $TMPVOL - $ARGUMENT`
       ossmix $CHANNEL -- -$NEWVOL
       rm $VOLSTORE
   else
       ossmix $CHANNEL -- -$ARGUMENT
   fi
}
case "$1" in
   '-i'|'--increase')
   increase
   ;;
   '-d'|'--decrease')
   decrease
   ;;
   '-t'|'--toggle')
   toggle
   ;;
   |'-h'|'--help')
   usage
   ;;
   *)
   err "Unrecognized option \`$1', see ossvol --help"
   ;;
esac

OSSv4.1 includes an ossmix which allows you to change volume in a relative fashion: 'ossmix vmix0-vol -- -2' and 'ossmix vmix-vol +2'. The two scripts below can be used to have this functionality in OSSv4.0:

lowervolume.sh

 #!/bin/sh
 CTRL=vmix0-vol
 VOL=$(ossmix | grep $CTRL | awk '{print $4}' | awk -F : '{print $1}')
 VOL=$(echo $VOL | awk '{print $1-2}')
 ossmix -- $CTRL $VOL

raisevolume.sh

 #!/bin/sh
 CTRL=vmix0-vol
 VOL=$(ossmix | grep $CTRL | awk '{print $4}' | awk -F : '{print $1}')
 VOL=$(echo $VOL | awk '{print $1+2}')
 ossmix $CTRL $VOL

You may wish to modify a different mixer control than vmix0-vol. In that case, you will need to change the value of CTRL above.

ALSA Emulation

• There are two main methods to achieve this:
  • libasound2's pcm-oss plugin:
    • Easiest method, but will not work with all programs. It works by making libasound use OSS via the pcm-oss plugin.
    • First, install the pcm-oss plugin. It is included in the alsa-plugins distribution.
      • Debian: install libasound2-plugins package.
    • Make sure an ~/.asoundrc file exists. It should contain the lines below:

 pcm.!default
 {
   type oss
   device /dev/dsp
 }
 mixer.!default
 {
   type oss
   device /dev/dsp
 }

• OSSv4 cuckoo module:
  • Harder, and will fail on some systems. It works by representing OSSv4 drivers as a soundcard to the ALSA modules, and supplying a "driver" for them.
  • Note that using pcm-oss conflicts with cuckoo - libasound needs to output to ALSA's device files, so rename ~/.asoundrc if you were using pcm-oss before doing this.

    Also, nearly all the commands below require root permissions.

  • First, goto /usr/lib/oss/cuckoo, and run "make install".
  • Second, we need to get the ALSA modules back:
    • Goto /lib/modules/$(uname -r)/, and extract the sound-preoss.tar.bz2 file.
    • We need to prune out the OSS emulation modules, since these might conflict with actual OSS, so run "rm -rf kernel/oss".
    • Follow this with "depmod -a" to
  • You can now run "modprobe cuckoo", and test with "speaker-test" etc. whether this works.
  • To make this stick, we need to edit the startup script, so that it loads cuckoo after loadings OSS. Edit $OSSLIBDIR/soundon.user, and add "modprobe cukoo" before "exit 0" line.

• A general problem with ALSA emulation is that some programs probe for driver support in the order "ALSA, OSS". So programs that were using OSS by default may now try to use the emulation with possibly inferior results. So if there are problems after installation, make sure the program uses the OSS support rather than the emulation.