scanner-record.sh

#!/bin/bash

#-------------------------------------------
# GENERAL NOTES
#
#-------------------------------------------
# This is a the old "simplex parrot" bash
# script stripped down to simply record
# captured audio that breaks a silence
# level and save it in timestamped files.
#
# If you patch a radio/scanner into your
# computer or Pi, you can have a set of
# recordings with date-time stamps
# for listening to later.
#-------------------------------------------
# Save in its own directory as scanner-record.sh
# create a "record" directory there and then run:
#
# ./scanner-record.sh
#-------------------------------------------
# Note:
# See the monitor.sh sister-script for ideas
# on how to watch for new recordings and
# then take action:
# https://pastebin.com/CnS58d95
#-------------------------------------------
# Use pavucontrol to select input and output
# or however is easiest/best for your
# working environment.
#
# Raspberry Pi may use alsa instead of
# pulse. You'll have to configure things
# with alsamixer or similar. It does seem
# to use pulseaudio nicely when pulse is
# installed.
#-------------------------------------------
# Code by Phillip J Rhoades (2024)
#-------------------------------------------

#-------------------------------------------
# HARDWARE NOTES
#
#-------------------------------------------
# When patching in from a Baofeng or such,
# I use an HT with an APRS cable and a
# mic/headphones splitter on one end
# to patch the radio into a Linux computer
# or a Raspberry Pi. The Pi will need a
# cheap USB soundcard. A USB soundcard
# could also help with ground issues
# (buzzing) on computers/laptops.
#
# You'll have to adjust input and output
# volumes on the computer and the output
# volume on the radio/scanner.
#
# You could improve on this basic setup
# in a number of ways but that's outside
# the scope of this "simple" project.
#
# If you're reading this script in monospace
# then this rough ASCII diagram of the setup
# might help you get a clearer idea:
#
#                    -->[PC Mic In]
# [HT]<-APRS->SPLIT-||
#                    <--[PC Sound Card Out] (NOT NEEDED)
#
# In some cases, a ground loop noise
# isolator or two might help with buzzing
# sounds between the computer and the HT.
#
# You can also use a cable that plugs into
# the tiny speaker-out of the radio and converts
# to the normal "headphone jack" of the computer
#
# Most scanners have a "headphone out" or
# "speaker out" port that you can plug into
# your computer mic port. You won't need
# to deal with APRS cables etc in that case.
#-------------------------------------------

#-------------------------------------------
# VARIABLE(S) TO CONTROL THINGS
#
#-------------------------------------------
# In order to keep the size down
# I convert the wav file to ogg in the
# background. You could easily set that to
# mp3 instead or you could skip conversion
# and just keep the original wavs, if you
# have plenty of disk space.
#
# Setting SAVERECS to 1 activates this
# feature and setting SAVERECS to 0
# disables it. (2020/02/26)
# If you just want to listen to the scanner
# on your computer, you might not save the
# recordings...
#-------------------------------------------

SAVERECS=1
SAVERECSDIR="./record"
#-------------------------------------------
# MORE "ELEGANT" EXITING
# (but still pretty much a hammer)
#
# Trap ctrl-c and call ctrl_c()
# to exit somewhat gracefully...
#-------------------------------------------

trap ctrl_c INT

function ctrl_c() {
          if test -f "./recording.wav"; then
               rm recording.wav
          fi
          echo
          echo "#-----------------------------------"
          echo "# Terminating the scanner recorder  "
          echo "#-----------------------------------"

          #-------------------------------------------
          # Kill the recorder and its parent process.
          #
          # Could issue shutdown -h instead in order
          # to shut down Linux/Pi computer completely.
          #-------------------------------------------

          kill -9 $PPID
          #shutdown -h now
}

#-------------------------------------------
# REPEATER RECORDER LOOP
#
#-------------------------------------------
# Loop until ctrl-c on keyboard or the
# DTMF command to terminate the repeater
#-------------------------------------------

while [ 1 ]; do
          echo
          echo "#-------------------------------"
          echo "# WAITING FOR AUDIO INPUT:"
          echo "#-------------------------------"
          # Silent record
          rec -V1 -c1 recording.wav rate 64k silence 1 0.1 1% 1 3.0 1% trim 0 300

          # Command for pass-through for scanner sound
          # while still recording a wav.
          # Some latency dependent on computer, but basically live.
          # Making the mic hot in alsa or pulse would have
          # less latency but other issues.
          #rec -V1 -c1 -t wav - rate 64k silence 1 0.1 1% 1 3.0 1% trim 0 300 |tee recording.wav |play -t wav -


          if test -f "./recording.wav"; then
               echo
               if [ $SAVERECS = 1 ]; then
                    # The timestamp is YEAR-MONTH+DAYOFMONTH-HOURMINUTESECONDS (2024-03-21-231107)
                    # Sorts better in an ls that way
                    TIMESTAMP=$(date +"%Y-%m-%d-%H%M%S")
                    mv recording.wav "$SAVERECSDIR/$TIMESTAMP.wav" #moving a file on the same filesystem is fast and cheap
                    (ffmpeg -loglevel quiet -i "$SAVERECSDIR/$TIMESTAMP.wav" "$SAVERECSDIR/$TIMESTAMP.ogg"; rm "$SAVERECSDIR/$TIMESTAMP.wav") & #Takes time. Do in background
               else
                    rm recording.wav #cleanup before restarting loop
               fi
          fi
done