Converts a folder full of MP3 files into AAC-LC M4A files with all metadata and artwork

mp3tom4a.sh

#!/bin/bash

# Define the source and destination directories
SRC_DIR="/path/to/folder/"
DEST_DIR="/path/to/folder/"

# Define audio quality
# 0.1 (Highest Quality) - 2 (Lowest Quality)
AUDIO_QUALITY=1
AUDIO_SAMPLING=44100

# Parallel Threads
THREADS=4

# Create the destination directory if it doesn't exist
mkdir -p "$DEST_DIR"

# Function to process each file
process_file() {
    FILE="$1"
    # Create the destination directory for this file, preserving the directory structure
    FILE_DIR=$(dirname "${FILE#$SRC_DIR}")
    mkdir -p "$DEST_DIR/$FILE_DIR"
    
    # Define the destination file name
    DEST_FILE="$DEST_DIR/$FILE_DIR/$(basename "$FILE" .mp3).m4a"

    # Skip if file already exists
    if [[ -f "$DEST_FILE" ]]; then
        return
    fi
    
    # Extract artwork to a temporary file
    TEMP_ARTWORK=$(mktemp).jpg
    ffmpeg -i "$FILE" -an -vcodec mjpeg -vframes 1 -y "$TEMP_ARTWORK"

    # Convert the audio
    ffmpeg -i "$FILE" -c:a aac -q:a $AUDIO_QUALITY -ar $AUDIO_SAMPLING -map_metadata 0 -vn "$DEST_FILE"
    
    # Embed the artwork into the m4a file using atomicparsley
    atomicparsley "$DEST_FILE" --artwork "$TEMP_ARTWORK" --overWrite
    
    # Remove the temporary artwork file
    rm "$TEMP_ARTWORK"
}

export -f process_file
export SRC_DIR
export DEST_DIR
export AUDIO_QUALITY
export AUDIO_SAMPLING

# Use GNU Parallel to process the files in parallel
find "$SRC_DIR" -type f -name '*.mp3' | parallel -j $THREADS process_file