it works

1 files changed, 42 insertions, 57 deletions

diff --git a/speakerWatchdog.sh b/speakerWatchdog.sh
index d78c40a..2597eaf 100644..100755
--- a/speakerWatchdog.sh
+++ b/speakerWatchdog.sh
@@ -1,65 +1,50 @@
 #! /bin/bash
-# Workaround for stupd 'powersave' 'feature' of Creative Speakers
+# Workaround for stupid 'powersave' 'feature' of Creative Speakers
 #
 # SJP 11 Dec 2021
 #
-#  This is just a stub for now
+# Record a snippet of default stream:
 
-# Which device is the audio output going to?
+# 0 rec -d  -n trim 0 .1 stat 
 
-# st33v@cr4y:~$ grep RUNNING /proc/asound/card*/pcm*/sub*/status
-# /proc/asound/card2/pcm0p/sub0/status:state: RUNNING
+#    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
 
-# That is fine, but the status remains as 'RUNNING' even after the speakers have turned themselves off...
-# So I'm going down the track of periodically sending a 'sound' to a loopback device
-# sudo modprobe snd-aloop
-# Now aply -l shows a new 'card' called Loopback.
+systemd-run --user --on-active=10m /usr/local/bin/speakerWatchdog.sh
 
-
-record one second of default stream:
-
-$ 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 1 second
-    stat
-
-Output:
-
-Input File     : 'default' (pulseaudio)
-Channels       : 2
-Sample Rate    : 48000
-Precision      : 16-bit
-Sample Encoding: 16-bit Signed Integer PCM
-
-In:0.00% 00:00:01.02 [00:00:00.00] Out:48.0k [      |      ]        Clip:0    
-Samples read:             96000
-Length (seconds):      1.000000
-Scaled by:         2147483647.0
-Maximum amplitude:     0.000000
-Minimum amplitude:     0.000000
-Midline amplitude:     0.000000
-Mean    norm:          0.000000
-Mean    amplitude:     0.000000
-RMS     amplitude:     0.000000
-Maximum delta:         0.000000
-Minimum delta:         0.000000
-Mean    delta:         0.000000
-RMS     delta:         0.000000
-Rough   frequency:  -2147483648
-Done.
-
-So if Max amplitude = 0 then we have silence!
-
-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.
+#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.