Thursday, 7 January 2016

Switch hdmi audio when TV is off using cec-client

I have a HDMI TV used as a computer monitor.

When the TV is turned on, the audio plays through the TV, so that the TV remote volume control works.

When  the TV is turned off, I want the audio to play through analog audio out so that I can still hear it.

I use the PulseEIGHT CEC controller and cec-client program to talk to the TV.

I have cec-client run as root under SOCAT to broadcast cec-data by UDP.

I have another SOCAT process running as the logged in user to pick up the data, monitor it for TV on/off status and move the playing audio streams.

It works, but is very rough.

In rc.local: /usr/local/bin/cec -s &

In gnome/cinnamon startup programs: /usr/local/bin/cec

And then the script:

#! /bin/bash

MYADDR=8 # because it is. I should probably read this from the cec-client output 
 
# 0 and 1 and the audio device indexes associated with the device names
# later I will normalise these too, but "pacmd list" will show yours.
ext() {
  pacmd set-default-sink alsa_output.pci-0000_00_1f.3.analog-stereo
  for input in $( pacmd list-sink-inputs | sed -e 's/index: //;t;d' )
  do pacmd move-sink-input $input 1
  done
}

hdmi() {
  pacmd set-default-sink alsa_output.pci-0000_01_00.1.hdmi-stereo-extra1
  for input in $( pacmd list-sink-inputs | sed -e 's/index: //;t;d' )
  do pacmd move-sink-input $input 0
  done
}

cec_client() {
  socat -u UDP4-RECV:4224,reuseaddr - | while read type _ _ dir rest
  do # echo "$type    $dir    :$rest"
     case "$rest" in
       "0f:36") echo "POWER OFF" ; ext ;;
       "(0): power status changed"*"to 'on'") echo "POWER ON" ; hdmi ;;
#       *"($MYADDR) as inactive source"*) echo INACTIVE ; ext ;;
#       *"($MYADDR) the active source"*) echo ACTIVATED ; hdmi ;;
#       *active*) echo "$type    $dir    $rest" ;;
# mmkeys-mate2mpris2
     esac
  done
}

cec_server() {
  read hostname _ < <( hostname )
  hex_hostname=$( echo -n "${hostname%.*}" | od -tx1 | sed -e '1!d;s/0* //' )

  <<< "tx 80 47 $hex_hostname" exec -a CEC socat -u -L/tmp/cec \
      EXEC:'cec-client -t p -p 2' UDP-DATAGRAM:127.0.0.1:4224,broadcast &

  wait
}

main() {
  if test "$1" = "-s"
  then cec_server
  else cec_client
  fi
}

main "$@"

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