#!/bin/bash

#🎩-tip: "Generate white noise to calm a baby" https://askubuntu.com/a/789472/362789
# 
# cf. this: 
# alias ocean_noise="play -r192000 -n synth brownnoise synth brownnoise mix synth sine amod 0.1 10" # 10-100% @ 0.1Hz (10s period waves)  🎩-tip: https://askubuntu.com/a/789472/362789

# cleanup old
rm *.opus *.wav

# Audio Copy and Paste Over (from sox manpage)
# acpo infile copy-start copy-stop paste-over-start outfile
function acpo() {
  local piece=`mktemp`.wav
  local part1=`mktemp`.wav
  local part2=`mktemp`.wav

  sox "$1" $piece trim $2 =$3
  sox "$1" $part1 trim 0 $4
  sox "$1" $part2 trim $4+$3-$2
  sox $part1 $piece $part2 "$5" splice $4 +$3-$2

  rm $piece $part1 $part2
}


# brownnoise is a white noise with a low-pass filter applied to it.

# generate 1 second of brown noise repeated for 30 seconds
sox -r192000 -e float -b 32 -n 1s_of_brown_noise_repeated_for_30s.wav synth 1 brownnoise repeat 30

# generate 30 seconds of brown noise
sox -r192000 -e float -b 32 -n 30s_of_brown_noise.wav synth 30 brownnoise

cp 30s_of_brown_noise.wav tmp.wav
# Insert the same first 1s sample (= the "frozen noise")
# into the 30s brown noise sample at times t = 2, 4, 6, …, 24, 26, 28
for i in `seq 2 2 28`; do
  echo $i
  acpo tmp.wav 0 1 $i out.wav
  mv out.wav tmp.wav 
done
mv tmp.wav 30s_of_brown_noise_with_1s_frozen_noise_every_2_seconds.wav

# encode all wav files in the current directory to opus
parallel opusenc {} {.}.opus ::: *.wav