#!/bin/bash

#
# If you have a computer with two independent audio devices (e.g.
# a laptop with embedded microphone and speaker and a USB headset)
# and you'd like the volume control (volume up, down and mute) to
# automatically switch to one device when it's plugged, this
# script will do so.
#
# This script only controls playback (not the capture device).
#
# Version:  1.0
# Author:   [email protected]
#
# References
# ==========
# o An excellent qdbus tutorial:
#
#   http://usrlocalbin.blogspot.ca/2008/04/qdbus-tutorial-part-one.html
#
# Glossary/Terms
# ==============
# o Default Device   - the computer's (e.g. laptop) speakers.  Normally
#                      controlled by Volume Up/Down/Mute.
#
# o Preferred Device - a secondary device (e.g. USB headset) which,
#                      when connected, you'd like to control via
#                      Volume Up/Down/Mute.
#
# Variables to set in this Script
# ===============================
# Mixer variables
# ---------------
# PREFERRED_MIXER
# DEFAULT_MIXER
#
# Device variables
# ----------------
# PREFERRED_DEVICE
# DEFAULT_DEVICE
#
# Preferred Card's /unique/ Identification
# PREFERRED_CARD
#
# Instructions
# ============
# Prerequisite
# ------------
# o kmix
# o The `preferred device' is connected to your machine (e.g.
#   USB headset)
#
# One-time setup
# --------------
# Ensure your preferred device has the correct priority within KDE:
#
# o System Settings > Multimedia > Phonon
# o Under the `Device Preference' tab, set the priority for your device.
#
# Determine the Default Mixer and Device
# --------------------------------------
# o kmix > Playback Devices
#
#   Both devices /must/ be listed.  If they're not listed, stop.
#
# o Settings > Select Master Channel ... > Current mixer: Playback Devices,
#   and ensure the default device is selected and if not, select it.  Click
#   `OK' to exit.
#
#   For example, the default device may be `Internal Audio Analog Stereo'
#
# o Set the DEFAULT_MIXER variable:
#
#   Open a terminal window and fetch the `current Master Mixer' value
#   using `qdbus' and set the DEFAULT_MIXER variable:
#
#   $ qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterMixer
#
# o Set the DEFAULT_DEVICE variable using the result from:
#
#   $ qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterControl
#
# Determine the Preferred Mixer and Device
# ----------------------------------------
# o kmix > Playback Devices
#
#   Both devices /must/ be listed.  If they're not listed, stop.
#
# o Settings > Select Master Channel ... > Current mixer: Playback Devices,
#   and select the `other' device (e.g. USB headset)
#
# o Set the PREFERRED_MIXER variable using the result from:
#
#   $ qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterMixer
#
# o Set the PREFERRED_DEVICE variable using the result from:
#
#   $ qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterControl
#
# Setting PREFERRED_CARD
# ----------------------
# This script checks /proc/asound/cards for the existence of the
# value specified by $PREFERRED_CARD  It's important that the value
# entered is unique; that it's not found in the value of the default
# device.
#
# To determine a value, type the following:
#
#    $ fgrep '[' /proc/asound/cards
#
# On my machine, I get the following values:
#
#    0 [Intel          ]: HDA-Intel - HDA Intel
#    1 [H760           ]: USB-Audio - Logitech Wireless Headset H760
#
# Given the above, as I want my Logitech to be the preferred device, I
# set PREFERRED_CARD="H760"
#

# Running the script
# ------------------
# Place this script, say, in ~/bin and have the script run when you log in:
#
#    System Settings > Startup and Shutdown > Autostart
#
# --- Configuration
#

#
# Mixer
#
PREFERRED_MIXER="PulseAudio::Playback_Devices:1"
DEFAULT_MIXER="PulseAudio::Playback_Devices:1"

#
# Device
#
PREFERRED_DEVICE="alsa_output.usb-GYROCOM_C_C_Co.__LTD_Audiotrak_ProDigy_CUBE-01-CUBE.analog-stereo"
DEFAULT_DEVICE="alsa_output.pci-0000_00_1b.0.analog-stereo"

#
# Card identifier
#
PREFERRED_CARD="CUBE"

#
# The number of seconds between checks.  The greater the number, the longer it'll
# take for us to detect a change.  :)
#
POLLING_FREQUENCY=3

#
# --- End of Configuration
#

#
# Main
#

#
# Loop forever
#
while [ 1 ] ; do
   CURRENT_MIXER=`qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterMixer`
   CURRENT_DEVICE=`qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.currentMasterControl`

   #
   # For debugging, it's easier if we not call fgrep within the if
   #
   fgrep '[' /proc/asound/cards | fgrep $PREFERRED_CARD 2>&1 >/dev/null
   CARD_INSTALLED=$?

   if [ $CARD_INSTALLED -eq 0 ]  ; then
      if [ "$CURRENT_MIXER" != "$PREFERRED_MIXER" -o "$CURRENT_DEVICE" != "$PREFERRED_DEVICE" ] ; then
         echo "`date` - Setting preferred device"
         qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.setCurrentMaster "$PREFERRED_MIXER" "$PREFERRED_DEVICE" 2>&1 > /dev/null
      fi
   else
      if [ "$CURRENT_MIXER" != "$DEFAULT_MIXER" -o "$CURRENT_DEVICE" != "$DEFAULT_DEVICE" ] ; then
         echo "`date` - Setting default device"
         qdbus org.kde.kmix /Mixers org.kde.KMix.MixSet.setCurrentMaster "$DEFAULT_MIXER" "$DEFAULT_DEVICE" 2>&1 > /dev/null
      fi
   fi
   sleep $POLLING_FREQUENCY
done

#
# Never reached
#