Transcodes a tree of FLAC files to OPUS.

transcode.sh

#!/bin/bash
#
# transcode.sh
#
# Transcodes a tree of FLAC files in a specified source directory to a matching tree of
# Opus files in the specified destination directory.

scriptName=$(basename "$0")
sourceDirectory="${1%/}"
destinationDirectory="${2%/}"

[ -d "$sourceDirectory" -a "$destinationDirectory" ] || { 
  echo $scriptName - Transcodes a tree of flac files to Opus.
  echo Usage: $scriptName source-dir dest-dir
  exit 1
}

function flac2opus() { sourceDirectory="$1"; destinationDirectory="$2"; flacFile="$3";
  opusFile="${destinationDirectory}/$(realpath --relative-to "$sourceDirectory" "${flacFile%%.flac}.opus")"

  [ -e "$opusFile" ] && return 0

  echo "[$flacFile] -> [$opusFile]"

  [ -d "$(dirname "$opusFile")" ] || mkdir -p "$(dirname "$opusFile")"

  flac -d -c -s "$flacFile" | \
  opusenc --quiet --bitrate 192 \
    --comment "$(metaflac --show-tag=artist      "$flacFile")" \
    --comment "$(metaflac --show-tag=album       "$flacFile")" \
    --comment "$(metaflac --show-tag=tracknumber "$flacFile")" \
    --comment "$(metaflac --show-tag=title       "$flacFile")" \
    --comment "$(metaflac --show-tag=genre       "$flacFile")" \
    --comment "$(metaflac --show-tag=date        "$flacFile")" \
    - "$opusFile"
}

export -f flac2opus

find "$sourceDirectory" -type f | grep -E '\.flac$' | parallel --ungroup --nice 20 flac2opus \'"$sourceDirectory"\' \'"$destinationDirectory"\' "{}"