Add mp3-to-mp4: convert MP3 to MP4 with static title card
Uses ffmpeg to generate an H.264/AAC video from an MP3 file with a centred title overlay. Supports optional background image (title at bottom) or solid colour (title centred). Includes spec, dryrun support, and 10 tests. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
This commit is contained in:
Paul O'Reilly
142
scripts/mp3-to-mp4
Executable file
142
scripts/mp3-to-mp4
Executable file
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#!/usr/bin/env bash
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set -uo pipefail
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SCRIPT_NAME="$(basename "$0")"
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# Defaults
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TITLE=""
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OUTPUT=""
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RESOLUTION="1920x1080"
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FONT_SIZE="72"
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FONT_COLOR="white"
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BG_COLOR="black"
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IMAGE=""
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DRYRUN=false
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usage() {
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cat <<EOF
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Usage: $SCRIPT_NAME [OPTIONS] <input.mp3>
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Convert an MP3 audio file into an MP4 video displaying a static title card.
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Arguments:
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<input.mp3> Path to the MP3 file (required)
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Options:
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-t, --title TEXT Title text to display (required)
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-o, --output PATH Output file path (default: input with .mp4 extension)
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-r, --resolution WxH Video resolution (default: 1920x1080)
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--font-size N Font size in pixels (default: 72)
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--font-color COLOR Font colour (default: white)
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--bg-color COLOR Background colour (default: black; ignored with --image)
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-i, --image PATH Background image (scaled to fill; title at bottom)
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-n, --dryrun Preview what would happen without creating files
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-h, --help Show this help message
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EOF
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}
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die() {
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echo "Error: $1" >&2
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exit 1
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}
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# Parse arguments
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INPUT=""
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while [[ $# -gt 0 ]]; do
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case "$1" in
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-t|--title) TITLE="$2"; shift 2 ;;
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-o|--output) OUTPUT="$2"; shift 2 ;;
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-r|--resolution) RESOLUTION="$2"; shift 2 ;;
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--font-size) FONT_SIZE="$2"; shift 2 ;;
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--font-color) FONT_COLOR="$2"; shift 2 ;;
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--bg-color) BG_COLOR="$2"; shift 2 ;;
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-i|--image) IMAGE="$2"; shift 2 ;;
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-n|--dryrun) DRYRUN=true; shift ;;
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-h|--help) usage; exit 0 ;;
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-*) die "unknown option: $1" ;;
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*) INPUT="$1"; shift ;;
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esac
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done
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# Validate
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[[ -z "$INPUT" ]] && die "no input file specified. See --help."
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[[ -f "$INPUT" ]] || die "file not found: $INPUT"
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[[ -z "$TITLE" ]] && die "--title is required"
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command -v ffmpeg >/dev/null 2>&1 || die "ffmpeg not found. Install with: sudo apt install ffmpeg"
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command -v ffprobe >/dev/null 2>&1 || die "ffprobe not found. Install with: sudo apt install ffmpeg"
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[[ -n "$IMAGE" && ! -f "$IMAGE" ]] && die "image not found: $IMAGE"
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# Default output path
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if [[ -z "$OUTPUT" ]]; then
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OUTPUT="${INPUT%.*}.mp4"
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fi
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# Get audio duration
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DURATION_SECS=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$INPUT" 2>/dev/null) \
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|| die "could not read audio duration from: $INPUT"
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# Format duration for display
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format_duration() {
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local secs="${1%.*}"
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local mins=$((secs / 60))
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local rem=$((secs % 60))
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if [[ $mins -gt 0 ]]; then
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echo "${mins}m ${rem}s"
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else
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echo "${rem}s"
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fi
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}
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DURATION_DISPLAY=$(format_duration "$DURATION_SECS")
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# Get ffmpeg version
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FFMPEG_VERSION=$(ffmpeg -version | head -1 | awk '{print $3}')
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if $DRYRUN; then
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echo "[dryrun] Input: $INPUT"
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echo "[dryrun] Output: $OUTPUT"
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echo "[dryrun] Title: $TITLE"
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echo "[dryrun] Duration: $DURATION_DISPLAY"
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echo "[dryrun] Resolution: $RESOLUTION"
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echo "[dryrun] Font size: $FONT_SIZE"
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echo "[dryrun] Font color: $FONT_COLOR"
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if [[ -n "$IMAGE" ]]; then
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echo "[dryrun] Background: $IMAGE (image)"
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else
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echo "[dryrun] Background: $BG_COLOR"
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fi
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echo "[dryrun] Dependencies OK: ffmpeg $FFMPEG_VERSION"
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echo "[dryrun] Would generate .mp4 video file"
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exit 0
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fi
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# Parse resolution
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WIDTH="${RESOLUTION%x*}"
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HEIGHT="${RESOLUTION#*x}"
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# Escape title for ffmpeg drawtext (colons and backslashes need escaping)
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ESCAPED_TITLE=$(echo "$TITLE" | sed "s/'/\\\\\\\\'/g" | sed 's/:/\\:/g')
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if [[ -n "$IMAGE" ]]; then
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# Image background: scale+crop to fill, title centred at bottom
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ffmpeg -y \
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-loop 1 -i "$IMAGE" \
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-i "$INPUT" \
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-vf "scale=${WIDTH}:${HEIGHT}:force_original_aspect_ratio=increase,crop=${WIDTH}:${HEIGHT},drawtext=text='${ESCAPED_TITLE}':fontsize=${FONT_SIZE}:fontcolor=${FONT_COLOR}:x=(w-text_w)/2:y=h-text_h-40" \
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-c:v libx264 -tune stillimage -pix_fmt yuv420p \
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-c:a aac -b:a 192k \
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-shortest \
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"$OUTPUT"
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else
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# Solid colour background: title centred
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ffmpeg -y \
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-f lavfi -i "color=c=${BG_COLOR}:s=${RESOLUTION}:d=${DURATION_SECS}" \
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-i "$INPUT" \
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-vf "drawtext=text='${ESCAPED_TITLE}':fontsize=${FONT_SIZE}:fontcolor=${FONT_COLOR}:x=(w-text_w)/2:y=(h-text_h)/2" \
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-c:v libx264 -tune stillimage -pix_fmt yuv420p \
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-c:a aac -b:a 192k \
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-shortest \
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"$OUTPUT"
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fi
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echo "$OUTPUT"
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