library_works/split_tracks

# split_tracks splits each track of the library.
#
# The library is mirrored for each type of split.
# karaoke: reduces the volume of the vocals by 80% and remixes it
# drum only: just the drums
# no drum: everything but the drums

#!/bin/bash

function make_drum() {
  mkdir -p "${dest_dir['no drums']}"
  quiet_drums="${actual_work_dir}/quiet drums.wav"
  wav_name="$(sed 's/\.flac$/.wav/' <<< "$file_name")"
  mixed_wav="${dest_dir['no drums']}/${wav_name}"
  final_opus="$(sed 's/\.wav$/.opus/' <<< "$mixed_wav")"

  echo sox -v "$volume_reduction_factor" "$drum_track" "$quiet_drums"
  sox -v "$volume_reduction_factor" "$drum_track" "$quiet_drums"
  echo sox -m "${nodrums[@]}" "$quiet_drums" "$mixed_wav"
  sox -m "${nodrums[@]}" "$quiet_drums" "$mixed_wav"
  rm "$quiet_drums"
  echo opusenc --comp 10 --downmix-stereo \
      --title "'${tags[TITLE]}'" --artist "'${tags[ARTIST]}'" \
      --album "'${tags[ALBUM]}'" --tracknumber "'${tags[TRACKNUMBER]}'" \
      --date "'${tags[DATE]}'" "'$mixed_wav'" "'$final_opus'"
  opusenc --comp 10 --downmix-stereo \
      --title "${tags[TITLE]}" --artist "${tags[ARTIST]}" \
      --album "${tags[ALBUM]}" --tracknumber "${tags[TRACKNUMBER]}" \
      --date "${tags[DATE]}" "$mixed_wav" "$final_opus"
  rm "$mixed_wav"
}

function make_drumonly() {
  mkdir -p "${dest_dir['drums only']}"
  echo echo dest dir: ${dest_dir['drums only']}
  echo drum track: "$drum_track"
  final_opus="${dest_dir['drums only']}/$(sed 's/\.flac$/.opus/' <<< "$file_name")"
  echo opusenc --comp 10 --downmix-stereo \
      --title "'${tags[TITLE]}'" --artist "'${tags[ARTIST]}'" \
      --album "'${tags[ALBUM]}'" --tracknumber "'${tags[TRACKNUMBER]}'" \
      --date "'${tags[DATE]}'" "'$drum_track'" "'$final_opus'"
  opusenc --comp 10 --downmix-stereo \
      --title "${tags[TITLE]}" --artist "${tags[ARTIST]}" \
      --album "${tags[ALBUM]}" --tracknumber "${tags[TRACKNUMBER]}" \
      --date "${tags[DATE]}" "$drum_track" "$final_opus"
}

function make_karaoke() {
  mkdir -p "${dest_dir[karaoke]}"
  quiet_vocals="${actual_work_dir}/quiet vocals.wav"
  wav_name="$(sed 's/\.flac$/.wav/' <<< "$file_name")"
  mixed_wav="${dest_dir['karaoke']}/${wav_name}"
  final_opus="$(sed 's/\.wav$/.opus/' <<< "$mixed_wav")"
  echo sox -v "$volume_reduction_factor" "$vocal_track" "$quiet_vocals"
  sox -v "$volume_reduction_factor" "$vocal_track" "$quiet_vocals"
  echo sox -m "${karaoke[@]}" "$quiet_vocals" "$mixed_wav"
  sox -m "${karaoke[@]}" "$quiet_vocals" "$mixed_wav"
  rm "$quiet_vocals"
  echo opusenc --comp 10 --downmix-stereo \
      --title "'${tags[TITLE]}'" --artist "'${tags[ARTIST]}'" \
      --album "'${tags[ALBUM]}'" --tracknumber "'${tags[TRACKNUMBER]}'" \
      --date "'${tags[DATE]}'" "'$mixed_wav'" "'$final_opus'"
  opusenc --comp 10 --downmix-stereo \
      --title "${tags[TITLE]}" --artist "${tags[ARTIST]}" \
      --album "${tags[ALBUM]}" --tracknumber "${tags[TRACKNUMBER]}" \
      --date "${tags[DATE]}" "$mixed_wav" "$final_opus"
  rm "$mixed_wav"
}

volume_reduction_factor='0.2'
src_library="${HOME}/flac"
work_dir="${HOME}/split"
actual_work_dir="${work_dir}/htdemucs_ft"

type -P 'demucs' &>/dev/null || (
  printf 'No demucs in path.\nInstall with `pip install demucs` or something.\n\n' >&2
  exit 1
)

find "$src_library" -type f -name '*.flac' | while read file; do
  if find "$work_dir" -type f &>/dev/null; then rm -rf "${work_dir}"/*; fi
  echo "file: $file"
  # file is full original path + filename
  src_dir="$(dirname "$file")"
  file_name="$(basename "$file")"
  unset tags
  unset dest_dir

  declare -A tags
  echo tag time
  while read -r line; do
    echo line: $line
    tag_type="$(cut -d= -f1 <<< "$line")"
    tag_val="$(cut -d= -f2- <<< "$line")"
    tags[$tag_type]="${tag_val^^}"
  done < <(metaflac --list --block-type=VORBIS_COMMENT "$file" | grep 'comment\[' | cut -d: -f2- | sed 's/^ //')


  declare -a ensure
  ensure=( TRACKNUMBER TITLE DATE ALBUM ARTIST )
  for tag_type in "${ensure[@]}"; do
    if [[ -z "${tags[$tag_type]}" ]]; then
      tags[$tag_type]="missing $tag_type"
    fi
  done

  declare -A dest_dir
  dest_dir['karaoke']="${src_dir//flac/karaoke}"
  dest_dir['drums only']="${src_dir//flac/drums only}"
  dest_dir['no drums']="${src_dir//flac/no drums}"

  demucs -n htdemucs_ft -o "$work_dir" --filename '{track} {stem}.{ext}' -j2 -d cpu --clip-mode rescale -- "$file" < /dev/tty
  unset files karaoke nodrums
  declare -a files karaoke nodrums
  readarray -t files < <(find "$work_dir" -type f -name '*.wav')
  unset vocal_track
  unset drum_track

  for cur_file in "${files[@]}"; do
    echo current file: "$cur_file"
    if ! grep -Eq 'drums\.wav$' <<< "$cur_file"; then
      nodrums+=("$cur_file") 
    else
      drum_track="$cur_file"
    fi

    if ! grep -Eq 'vocals\.wav$' <<< "$cur_file"; then
      karaoke+=("$cur_file")
    else
      vocal_track="$cur_file"
    fi
  done 

  for i in "${nodrums[@]}"; do
    printf 'Drum practice: %s\n' "$i"
  done
  if [[ -z "$drum_track" ]]; then
    printf 'No drum track. Will not create a drum practice file.\n'
  else
    make_drum
    make_drumonly
  fi
  for i in "${karaoke[@]}"; do
    printf 'Karaoke practice: %s\n' "$i"
  done
  if [[ ! "$vocal_track" ]]; then
    printf 'No vocal track. Will not create a karaoke file.\n'
  else
    make_karaoke
  fi
done