MV Render

Render music videos with waveform visualization and synced lyrics from audio + lyrics input.

Prerequisites

• Remotion project at scripts/ directory within this skill

• Node.js + npm dependencies installed

• ffprobe available (for audio duration detection)

First-Time Setup

Before first use, check and install dependencies:

1. Check Node.js

node --version

2. Install npm dependencies

cd {project_root}/{.claude or .codex}/skills/acestep-simplemv/scripts && npm install

3. Check ffprobe

ffprobe -version

If ffprobe is not available, install ffmpeg (which includes ffprobe):

• Windows: choco install ffmpeg or download from https://ffmpeg.org/download.html and add to PATH

• macOS: brew install ffmpeg

• Linux: sudo apt-get install ffmpeg (Debian/Ubuntu) or sudo dnf install ffmpeg (Fedora)

Quick Start

cd {project_root}/{.claude or .codex}/skills/acestep-simplemv/ ./scripts/render-mv.sh --audio /path/to/song.mp3 --lyrics /path/to/song.lrc --title "Song Title"

Output: MP4 file at out/<audio_basename>.mp4 (or custom --output path).

Script Usage

./scripts/render-mv.sh --audio <file> --lyrics <lrc_file> --title "Title" [options]

Options: --audio Audio file path (absolute paths supported) --lyrics LRC format lyrics file (timestamped) --lyrics-json JSON lyrics file [{start, end, text}] (alternative to --lyrics) --title Video title (default: "Music Video") --subtitle Subtitle text --credit Bottom credit text --offset Lyric timing offset in seconds (default: -0.5) --output Output file path (default: out/<audio_basename>.mp4) --codec h264|h265|vp8|vp9 (default: h264) --background Background image file path (if omitted, uses animated gradient) --browser Custom browser executable path (Chrome/Edge/Chromium) --max-size Max output file size in MB (e.g. 24). Auto-compresses if exceeded. Use for IM platforms (WhatsApp≤16MB, Discord≤25MB, Telegram≤50MB)

Environment variables: BROWSER_EXECUTABLE Path to browser executable (overrides auto-detection)

Browser Detection

Remotion requires a Chromium-based browser for rendering. The script auto-detects browsers in this priority order:

• BROWSER_EXECUTABLE environment variable

• --browser CLI argument

• Remotion cache (chrome-headless-shell , downloaded by Remotion)

• System Chrome (auto-uses --chrome-mode=chrome-for-testing )

• System Edge (pre-installed on Windows 10/11, auto-uses --chrome-mode=chrome-for-testing )

• System Chromium (auto-uses --chrome-mode=chrome-for-testing )

Important: New versions of Chrome/Edge removed the old headless mode. When using regular Chrome/Edge/Chromium, the script automatically sets --chrome-mode=chrome-for-testing (which uses --headless=new ). When using chrome-headless-shell , it uses the default headless-shell mode (which uses --headless=old ). This is handled transparently.

If no browser is found, Remotion will attempt to download chrome-headless-shell from Google servers. This will fail if Google servers are inaccessible from your network.

Workarounds for restricted networks

Since Edge is pre-installed on Windows 10/11, it should be auto-detected without any manual configuration. The script automatically detects Chrome/Edge and uses the correct headless mode. If auto-detection fails:

Option 1: Set environment variable

export BROWSER_EXECUTABLE="/path/to/msedge.exe"

Option 2: Pass as CLI argument

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "Song" --browser "/path/to/msedge.exe"

Option 3: Enable proxy and let Remotion download chrome-headless-shell

Examples

Basic render

./scripts/render-mv.sh --audio /tmp/abc123_1.mp3 --lyrics /tmp/abc123.lrc --title "夜桜"

Custom output path

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "My Song" --output /tmp/my_mv.mp4

With subtitle and credit

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "Song" --subtitle "Artist Name" --credit "Generated by ACE-Step"

With background image

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "Song" --background /path/to/cover.jpg

Compress for Discord upload (max 25MB)

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "Song" --max-size 24

Compress for WhatsApp (max 16MB)

./scripts/render-mv.sh --audio song.mp3 --lyrics song.lrc --title "Song" --max-size 15

IM Platform Upload Limits

When sending MV to chat platforms, use --max-size to auto-compress:

Platform Limit Recommended --max-size

WhatsApp 16MB 15

Discord (free) 25MB 24

Telegram 50MB 48

Slack (free) 1GB

The compression uses ffmpeg two-pass encoding to achieve the best quality within the size constraint.

Container / Docker Font Support

When running in containers (e.g. OpenClaw), CJK fonts may not be pre-installed, causing lyrics to render as □ boxes. The script automatically:

• Detects if CJK fonts are available (via fc-list )

• Attempts to install fonts-noto-cjk (Debian/Ubuntu), font-noto-cjk (Alpine), or google-noto-sans-cjk-fonts (Fedora/RHEL)

• Falls back with a warning and manual install instructions if auto-install fails

If auto-install doesn't work, manually install fonts before rendering:

Debian/Ubuntu

apt-get install -y fonts-noto-cjk

Alpine

apk add font-noto-cjk

Fedora/RHEL

dnf install -y google-noto-sans-cjk-fonts

File Naming

IMPORTANT: Use the audio file's job ID as the output filename to avoid overwriting. Do NOT use custom names like --output my_song.mp4 . Let the default naming handle it (derives from audio filename).

Default output uses the audio filename as base:

• Audio: acestep_output/{job_id}_1.mp3

• Lyrics: acestep_output/{job_id}_1.lrc

• Video: Pass --output acestep_output/{job_id}.mp4 (use the job ID from the audio file)

Example: if audio is chatcmpl-abc123_1.mp3 , pass --output acestep_output/chatcmpl-abc123.mp4

Title Guidelines

• Keep --title short and single-line (max ~50 chars, auto-truncated)

• Use --subtitle for additional info

• Do NOT put newlines in --title

Good: --title "Open Source" --subtitle "ACE-Step v1.5"

Bad: --title "Open Source - ACE-Step v1.5\nCelebrating Music AI"

Notes

• Audio files with absolute paths are auto-copied to public/ by render.mjs

• Duration is auto-detected via ffprobe

• Typical render time: ~1-2 minutes for a 90s song

• Output resolution: 1920x1080, 30fps