powerhour/powerhour.sh

#!/usr/bin/env bash

if [[ $# -lt 1 || $# -gt 2 ]]; then
  echo "Usage: $0 <filename> <separator>"
  exit 1
fi

if [ ! -f $1 ]; then
  echo "$1 is not a file"
fi

file=$1
sep=$2

FFMPEG="docker run -ti --rm -v $(pwd):/data -w /data linuxserver/ffmpeg -hide_banner -loglevel error"
FFPROBE="docker run -ti --rm -v $(pwd):/data -w /data --entrypoint ffprobe linuxserver/ffmpeg"

CLIP_LEN=60

audio_len=$($FFPROBE -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 $file | tr -d '\r\n' | sed 's/\..*$//')
max_start=$(expr $audio_len - $CLIP_LEN)

# first make a bunch of 60s clips with random start positions
echo "Making the clips"
for i in {0..59}; do
  echo -n "$i "
  rand_start=$(($RANDOM % $max_start))
  outfile="clip-$i.wav"
  $FFMPEG -ss $rand_start -t 60 -i $file $outfile
done
echo

# next loop over those clips and shrink them appropriately
echo "Adjusting tempo"
for i in {1..59}; do
  echo -n "$i "
  outfile="clip-$i.wav"
  infile="_$outfile.tmp"
  mv $outfile $infile
  tempo=$(echo "1 + (0.02 * $i)"| bc)
  $FFMPEG -i $infile -filter:a "atempo=$tempo" -vn $outfile
  rm $infile
done
echo

# stitch em together
# Using a file here because i need to access it in docker
echo "Stitching them together"
>_concat
for i in {0..59}; do
  echo "file clip-$i.wav" >>_concat
  [ "$sep" != "" ] && echo "file $sep" >>_concat
done

$FFMPEG -f concat -safe 0 -i _concat -c copy powerhour.wav