Make the Spectrogram service run as a loop

The Spectrogram service was stopping after it completed it's work (no issue here) and the system would start it again 10 seconds later, sometimes it would stop and start multiple times a second (no file to analyse maybe)

Added a while loop to that it would just keep running and sleeping for the number of seconds of the recording length setting.

scripts/spectrogram.sh

@@ -1,8 +1,20 @@
 #!/usr/bin/env bash
+# set -x
 # Make sox spectrogram
 source /etc/birdnet/birdnet.conf
+
+# Time to sleep between generating spectrogram's, default set the recording length
+# To try catch the spectrogram as soon as possible run at a smaller intervals
+SLEEP_DELAY=$((RECORDING_LENGTH / 4))
+
+# Continuously loop generating a spectrogram every 10 seconds
+while true; do
   analyzing_now="$(cat $HOME/BirdNET-Pi/analyzing_now.txt)"
+
   if [ ! -z "${analyzing_now}" ] && [ -f "${analyzing_now}" ]; then
     spectrogram_png=${EXTRACTED}/spectrogram.png
-  sox -V1 "${analyzing_now}" -n remix 1 rate 24k spectrogram -c "${analyzing_now//$HOME\/}" -o "${spectrogram_png}"
+    sox -V1 "${analyzing_now}" -n remix 1 rate 24k spectrogram -c "${analyzing_now//$HOME\//}" -o "${spectrogram_png}"
   fi
+
+  sleep $SLEEP_DELAY
+done