mxsr / Audio Encoder Script

#!/usr/bin/env bash # Strict mode for robust error handling set -euo pipefail # Default variables INPUT_FILE="" OUTPUT_FILE="" CODEC="opus" ENCODER_TYPE="native" STREAM_INDEX="0" BITRATE_PER_CHANNEL=64 # kbps per channel for Opus usage() { cat <<EOF Usage: $(basename "$0") -i <input_media> [OPTIONS] A script to extract and encode a specific audio track from a movie file to FLAC or Opus. Options: -i <file> Input media file (video or audio) -o <file> Output file name (optional; auto-generated if omitted) -c <codec> Target codec: 'opus' or 'flac' (default: opus) -e <type> Encoder type: 'native' (ffmpeg) or 'external' (flac/opusenc) (default: native) -s <index> Audio stream index to select (default: 0, which is the first audio track) -h Show this help message Examples: $(basename "$0") -i movie.mkv -c opus -e native $(basename "$0") -i movie.mp4 -c flac -s 1 -o my_custom_audio.flac EOF exit 1 } # Parse command line arguments while getopts "i:o:c:e:s:h" opt; do case "$opt" in i) INPUT_FILE="$OPTARG" ;; o) OUTPUT_FILE="$OPTARG" ;; c) CODEC=$(echo "$OPTARG" | tr '[:upper:]' '[:lower:]') ;; e) ENCODER_TYPE=$(echo "$OPTARG" | tr '[:upper:]' '[:lower:]') ;; s) STREAM_INDEX="$OPTARG" ;; h|*) usage ;; esac done # Validate inputs if [[ -z "$INPUT_FILE" || ! -f "$INPUT_FILE" ]]; then echo "Error: Input file not found or not specified." usage fi if [[ "$CODEC" != "opus" && "$CODEC" != "flac" ]]; then echo "Error: Codec must be 'opus' or 'flac'." exit 1 fi if [[ "$ENCODER_TYPE" != "native" && "$ENCODER_TYPE" != "external" ]]; then echo "Error: Encoder type must be 'native' or 'external'." exit 1 fi # Validate stream index is a number if ! [[ "$STREAM_INDEX" =~ ^[0-9]+$ ]]; then echo "Error: Stream index must be a non-negative integer." exit 1 fi # Check dependencies command -v ffmpeg >/dev/null 2>&1 || { echo "Error: ffmpeg is required."; exit 1; } command -v ffprobe >/dev/null 2>&1 || { echo "Error: ffprobe is required."; exit 1; } if [[ "$ENCODER_TYPE" == "external" ]]; then if [[ "$CODEC" == "flac" ]] && ! command -v flac >/dev/null 2>&1; then echo "Error: 'flac' tool is required for external flac encoding." exit 1 fi if [[ "$CODEC" == "opus" ]] && ! command -v opusenc >/dev/null 2>&1; then echo "Error: 'opusenc' tool is required for external opus encoding." exit 1 fi fi # Determine number of audio channels of the selected audio stream CHANNELS=$(ffprobe -v error -select_streams "a:${STREAM_INDEX}" -show_entries stream=channels -of default=noprint_wrappers=1:nokey=1 "$INPUT_FILE") if [[ -z "$CHANNELS" ]]; then echo "Error: Could not detect audio channels for stream index a:${STREAM_INDEX} in $INPUT_FILE. (Does that track exist?)" exit 1 fi echo "Detected $CHANNELS channel(s) in audio stream ${STREAM_INDEX}." # Calculate Opus bitrate (ignored for lossless FLAC) TOTAL_BITRATE=$(( CHANNELS * BITRATE_PER_CHANNEL )) # Determine output filename if not provided by user if [[ -z "$OUTPUT_FILE" ]]; then OUTPUT_FILE="${INPUT_FILE%.*}_track${STREAM_INDEX}.${CODEC}" fi # Handle channel mapping for native Opus (required for >2 channels) # Family 0 is for mono/stereo. Family 1 is for surround (3 to 8 channels). MAPPING_FAMILY=0 if [[ "$CHANNELS" -gt 2 ]]; then MAPPING_FAMILY=1 fi # Set FFmpeg logging profiles # Native: Hide banner, only show errors, but keep the progress bar (-stats) FFMPEG_NATIVE_LOG="-hide_banner -loglevel error -stats" # External: Completely silent so it doesn't garble the external tool's output FFMPEG_EXT_LOG="-hide_banner -loglevel quiet" echo "Starting encode: Target=$CODEC | Encoder=$ENCODER_TYPE | Stream=a:${STREAM_INDEX} | Output=$OUTPUT_FILE" # Execute encoding based on user choices if [[ "$CODEC" == "opus" ]]; then echo "Target Bitrate: ${TOTAL_BITRATE}k" if [[ "$ENCODER_TYPE" == "native" ]]; then ffmpeg $FFMPEG_NATIVE_LOG -y -i "$INPUT_FILE" -map "0:a:${STREAM_INDEX}" \ -c:a libopus -b:a "${TOTAL_BITRATE}k" -vbr on -mapping_family "$MAPPING_FAMILY" \ "$OUTPUT_FILE" elif [[ "$ENCODER_TYPE" == "external" ]]; then # Pipe 24-bit PCM WAV to opusenc. ffmpeg $FFMPEG_EXT_LOG -y -i "$INPUT_FILE" -map "0:a:${STREAM_INDEX}" -f wav -c:a pcm_s24le - | \ opusenc --bitrate "$TOTAL_BITRATE" - "$OUTPUT_FILE" fi elif [[ "$CODEC" == "flac" ]]; then if [[ "$ENCODER_TYPE" == "native" ]]; then # Native FLAC encoding ffmpeg $FFMPEG_NATIVE_LOG -y -i "$INPUT_FILE" -map "0:a:${STREAM_INDEX}" \ -c:a flac -compression_level 8 \ "$OUTPUT_FILE" elif [[ "$ENCODER_TYPE" == "external" ]]; then # Pipe 24-bit PCM WAV to external FLAC encoder. ffmpeg $FFMPEG_EXT_LOG -y -i "$INPUT_FILE" -map "0:a:${STREAM_INDEX}" -f wav -c:a pcm_s24le - | \ flac -8 - -o "$OUTPUT_FILE" fi fi echo -e "\nEncoding complete: $OUTPUT_FILE"