A simple script to convert popular audio file formats to Red Book standard audio files for burning to CD-R media.

audio-cd-convert.sh

#!/usr/bin/env bash
set -euo pipefail

# Configuration
SRC_DIR="${1:-.}"
WAV_DIR="wav"
TOC_FILE="$WAV_DIR/audio.toc"
SAMPLE_RATE=44100
BIT_DEPTH=16
CHANNELS=2
CD_FRAME_SAMPLES=588  # 1 frame = 2352 bytes / (2 channels * 2 bytes per sample)

mkdir -p "$WAV_DIR"

echo "Converting audio files to WAV and aligning to CD frames..."

# Collect supported audio files
mapfile -t INPUTS < <(
    find "$SRC_DIR" -maxdepth 1 -type f \( \
        -iname "*.flac" -o \
        -iname "*.wav"  -o \
        -iname "*.aiff" -o \
        -iname "*.aif"  -o \
        -iname "*.mp3"  -o \
        -iname "*.ogg"  -o \
        -iname "*.m4a"  -o \
        -iname "*.aac" \
    \) | sort
)

for input in "${INPUTS[@]}"; do
    base="$(basename "$input")"
    name="${base%.*}"
    wav="$WAV_DIR/$name.wav"

    echo "  $input -> $wav"

    # Convert with sox to stereo 16-bit 44.1kHz WAV
    sox "$input" -r "$SAMPLE_RATE" -b "$BIT_DEPTH" -c "$CHANNELS" "$wav"

    # Align to CD frame boundary
    total_samples=$(soxi -s "$wav")
    remainder=$(( total_samples % CD_FRAME_SAMPLES ))
    if [ "$remainder" -ne 0 ]; then
        pad_samples=$(( CD_FRAME_SAMPLES - remainder ))
        echo "    Padding $pad_samples samples to CD frame..."
        # pad 0 seconds at start, pad_samples/44100 seconds at end
        sox "$wav" "$wav.tmp.wav" pad 0 $(awk "BEGIN {printf \"%.6f\", $pad_samples/$SAMPLE_RATE}")
        mv "$wav.tmp.wav" "$wav"
    fi
done

echo "Generating TOC file in $WAV_DIR..."

{
    echo "CD_DA"
    for wav in "$WAV_DIR"/*.wav; do
        cat <<EOF

TRACK AUDIO
FILE "$wav" 0
EOF
    done
} > "$TOC_FILE"

echo
echo "Done."
echo
echo "Next steps:"
echo "  1. Insert a blank CD-R"
echo "  2. (Optional) Test with cdrdao:"
echo "     sudo cdrdao write --simulate --device /dev/cdrom $TOC_FILE"
echo "  3. Burn:"
echo "     sudo cdrdao write --speed 8 --device /dev/cdrom $TOC_FILE"
echo "     (or wodim with padding):"
echo "     sudo wodim -v dev=/dev/sr0 -dao -audio -pad wav/*.wav"