gnipbao/framevelo

framevelo 是做什么的？

FrameVelo turns a page that draws its frames from code into an MP4. Frames stay on the GPU (drawElementImage or the page's canvas) and go straight to the hardware encoder, so a render takes a fraction of the CPU and memory of screenshot-based renderers. HyperFrames projects are compiled by the official HyperFrames pipeline; FrameVelo replaces only capture and encoding.

Calling it

Use the MCP tools of this plugin when they are available. On its very first start the plugin installs FrameVelo into ~/.cache/framevelo (about a minute); if the tools are missing right after installing the plugin, wait and reconnect (/mcp), or use the CLI below.

• render: renders; returns the output path, frame count, size, timings, warnings and the last log lines.
• doctor: checks Node, FFmpeg, Chrome, drawElementImage, the hardware encoders and HyperFrames support.
• install_browser: downloads chrome-headless-shell (about 100 MB) when no Chrome 151+ is installed.

Without the tools, run the CLI. --json prints the result (or {"error": ...}) on stdout:

npx -y -p github:gnipbao/framevelo -p @hyperframes/[email protected] -p @hyperframes/[email protected] framevelo render /abs/project -o /abs/out.mp4 --json -q

The first npx run installs for about half a minute. If you will render often, suggest that the user install it once: npm install -g github:gnipbao/framevelo @hyperframes/[email protected] @hyperframes/[email protected]. The CLI takes the same options as the tool, as flags (--frames 30 --quality draft). framevelo render --help lists them.

Use absolute paths. Run one render at a time: they share the single hardware encoder, and the MCP server queues them anyway.

Workflow

1. Find the input: a project directory with index.html, or an .html file. Duration, fps and size come from the page (HyperFrames data-duration/data-fps/data-width, window.__framevelo.duration, the GSAP timeline length, window.__comp). Pass them only to override.
2. Preview a slice when the composition is new or just changed: { input, output: "/tmp/preview.mp4", start: 2, frames: 30, quality: "draft" }. This takes seconds. Look at a frame: ffmpeg -v error -ss 0.5 -i /tmp/preview.mp4 -frames:v 1 /tmp/preview.png, then view the PNG.
3. Render in full with defaults. Add scale: 2 for 4K from a 1080p layout, or subframes: 3 for motion blur.
4. Check the result: frames is the count you expected; audio is true when the composition has sound; read warnings. screenshotFrames > 0 means some intervals failed verification and were captured by screenshot (still correct, just slower).
5. Report the output path, length, size and how long it took (wallMs).

Making a page renderable

Every frame must be a pure function of time. FrameVelo seeks the page through the first of these it finds:

1. window.__framevelo = { seek(t), duration, fps }. seek may return a promise.
2. window.__seek(t), with an optional window.__duration.
3. A paused GSAP timeline on window.__timelines.main (or the first key).

<canvas id="scene" width="1920" height="1080"></canvas>
<script>
  const g = document.getElementById("scene").getContext("2d");
  function draw(t) {
    g.fillStyle = "#05060a";
    g.fillRect(0, 0, 1920, 1080);
    g.fillStyle = "#6cf";
    g.fillRect(200 + 300 * t, 500, 120, 120);
  }
  window.__framevelo = { duration: 4, seek: draw };
</script>

• Put footage on the timeline with <video data-start="1.5" src="clip.mp4"> (optional data-media-start, data-duration, data-playback-rate). FrameVelo seeks it to the exact frame; long-GOP sources get a cached all-intra proxy.
• Math.random is seeded, so renders repeat.
• requestAnimationFrame loops, CSS transitions, Date.now() and performance.now() animations cannot be seeked. Move them onto seek(t) or a paused GSAP timeline.
• Wait for assets inside the page (fonts, images) before exposing the driver, or return a promise from seek.

Options worth knowing

Need	Arguments
Quick check	frames: 30, quality: "draft", start: <s>
4K from a 1080p layout	scale: 2
Vertical page without declared size	viewport: "1080x1920"
Smaller files	codec: "hevc"
Motion blur	subframes: 3 (and shutter, default 0.5)
Replace the soundtrack	audio: "/abs/music.m4a"
Capture one element	selector: "#stage"
Transparent DOM over a color	background: "#000"
code-video skill not found	mounts: {"/@skill/": "/abs/path/to/code-video"}
HyperFrames project as a plain page	hyperframes: false

When it fails

Message	Do this
Chrome not found	Call install_browser (or run framevelo browser install), then render again.
FFmpeg / FFprobe failing in doctor	Ask the user to install FFmpeg (brew install ffmpeg). Don't install system software yourself.
The page exposes no way to seek time	The page needs a time driver; see "Making a page renderable".
Unknown duration	Pass duration or frames, or declare the duration in the page.
The composition failed to set up	A script error in the composition. Fix the page; the message carries the page error.
No element matches selector / Nothing to capture / has no size	Point selector at a visible element with a size, or fix the layout.
Rendering a HyperFrames project needs ... @hyperframes/producer	Use the npx -p @hyperframes/... command above, or install the packages next to FrameVelo.
No paint event within ...	The page stopped painting; usually a hung script. Check it in a browser.

Renders are atomic: a failed or cancelled render leaves no output file.