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#! /bin/bash
# Workaround for stupid 'powersave' 'feature' of Creative Speakers
#
# SJP 11 Dec 2021
#
# Dependencies: sox (required)
# xprintidle (not required)
#
# Record a snippet of default stream:
# 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)
maxAmp=$(rec -d -c1 -n trim 0 .5 stat 2>&1 | grep 'Maximum amp' | awk {'print $3'})
# xprintidle is logfile eyecandy. Not necessary for the script to work
echo $(xprintidle) Max Amplitude = "$maxAmp" | \
systemd-cat -t "idle time (msec) & audio level " -p notice
timerMins=10m # default timer duration
if [ "$maxAmp" == "0.000000" ]; then
# We have silence
if [ ! -f "/tmp/silencemarker" ] ; then
# This is the first instance of silence after detecting noise
touch /tmp/silencemarker
fi
# Play the tone.
# Even though there may have been some sounds played since the previous
# observation, let's play it safe.
echo 'Play inaudible tone (20 Hz for 2 sec)'
play -nq synth 2 sine 20 fade 0.4 0
else
# Sound was detected so remove the marker file if it is there
if [ -f "/tmp/silencemarker" ] ; then
rm /tmp/silencemarker
fi
fi
# Set a timer. Accuracy is 'per-minute' so the interval may be
# as long as 11 minutes. This is ok for Creative Gigaworks; they turn off after 11+mins.
systemd-run --user --on-active=${timerMins} /usr/local/bin/speakerSqueaker.sh
#TODO: possibly allow actual turn off if no sound has been heard for a 'long' time
#TODO: Measure actual power consumption to see how futile erp actually is
# http://eco3e.eu/regulations/erp-directive/
#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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