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#! /bin/bash
# Workaround for stupid 'powersave' 'feature' of Creative Speakers
#
# SJP 11 Dec 2021
#
# Record a snippet of default stream:
# 0 rec -d -n trim 0 .1 stat
# rec sox in record mode
# -d default input
# -n direct output to /dev/null
# trim 0 .1 duration 0.1 second
# stat write info about the audio stream
# 2>&1 redirect stderr to stdout
# | pipe
# grep finds this line: Minimum amplitude: 0.000000
# | pipe
# awk ruturns just the third word (the number)
#echo hello $USER | systemd-cat -t AlexySayle -p warning
maxAmp=$(rec -d -c1 -n trim 0 .1 stat 2>&1 | grep 'Maximum amplitude' | awk {'print $3'})
echo Max Amplitude = $maxAmp
if [ "$maxAmp" == "0.000000" ]; then
# if Max amplitude = 0 then we have silence!
if [ -f "/tmp/silencemarker" ] ; then
# There was silence last time we checked, so play the tone
echo Play the sound
play -nq synth 1 sine 40 fade 0.2 0
rm /tmp/silencemarker
else
touch /tmp/silencemarker
fi
else
if [ -f "/tmp/silencemarker" ] ; then
rm /tmp/silencemarker
fi
fi
systemd-run --user --on-active=10m /usr/local/bin/speakerWatchdog.sh
#to generate a tone that is not audible:
#play -n synth 1 sine 40 fade .2 0
#
# play sox alias
# -n dummy input file
# synth synthesise a sound
# sine sine wave [the default, so not strictly necessary]
# 40 Hz
# fade fade in from zero volume to max volume over 200 msec.
# '0' says fade out at end over same period.
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