video

name	video
description	Create polished narrated MP4 videos with Remotion in the sandbox.

Video

Create one narrated 1920×1080 MP4 at 30 fps in /workspace. Use the baked /opt/remotion harness and dependencies. Never install or download anything. The sandbox has no network.

Plan before rendering

Draft the complete deck specification first. For every slide include its on-screen text and narration line. Keep this specification unchanged: pass its narration lines to synthesize_narration, and later use the full specification as markdown_representation. It is the durable accessible and editable source; scene files and props.json are ephemeral.

Refuse requests above the 12-scene product limit rather than silently shortening them. The selected composition must also be at most 180 seconds.

Composition rules

• Give each slide one clear purpose. Keep safe outer margins, readable body contrast, restrained motion, and every shape on the 1920×1080 canvas.
• The harness supplies sequencing, narration audio, and the SurfSense watermark. Do not add another watermark or audio element.
• Use only these system-installed font families: Inter for normal text, Lora for editorial titles or quotes, and JetBrains Mono for code and figures. No other family is available reliably offline. Do not use loadFont, @font-face, or @remotion/google-fonts.
• Write one complete, self-contained TSX module per slide. Each module must import every dependency it uses and have a default component export. The harness writes the module verbatim: it does not inject globals, strip imports, or rewrite exports. Dependencies must already exist in baked node_modules.

Use this exact module shape:

import type React from "react";
import {AbsoluteFill, useCurrentFrame, useVideoConfig} from "remotion";
import {stagger} from "../../stagger";

const Scene: React.FC = () => {
  const frame = useCurrentFrame();
  const {fps} = useVideoConfig();
  const entrance = stagger(frame, fps, 0, 1);

  return (
    <AbsoluteFill
      style={{
        alignItems: "center",
        backgroundColor: "#101828",
        color: "white",
        fontFamily: "Inter",
        justifyContent: "center",
      }}
    >
      <h1 style={{fontSize: 96, ...entrance}}>A clear opening</h1>
    </AbsoluteFill>
  );
};

export default Scene;

There are no assumed React, AbsoluteFill, useCurrentFrame, useVideoConfig, interpolate, spring, staticFile, Audio, or stagger globals. Import only what that scene uses.

Build loop

1. Copy /opt/remotion to a fresh per-render work directory.
2. Call synthesize_narration once with every {slide_number, transcript} and that work directory. It writes files under public/ and returns filenames. Never fetch audio yourself.
3. Write props.json with fps, min_duration_in_frames, and ordered {slide_number, code, audio} scenes. Use returned audio filenames exactly.
4. Run node render.mjs --preflight props.json. It validates input, writes the verbatim modules, bundles them, selects the composition, and enforces the 180-second limit without rendering frames.
5. Run node render.mjs --stills props.json /tmp/stills. Inspect each scene's start, middle, and end PNG plus contact-sheet.png for clipping, overflow, contrast, hierarchy, blank frames, and safe margins.
6. If preflight or still review fails, make one coordinated repair and repeat preflight and still review once. If it still fails, stop; do not keep repairing.
7. Run the full node render.mjs props.json /workspace/out.mp4. The harness measures narration with parseMedia, derives timing, segments long renders, and concatenates them. Do not hand-calculate audio frame counts.
8. Call verify_artifact(path="/workspace/out.mp4"). If it reports a blocking finding, make one final repair, then run preflight, still review, render, and verification once more. A second verification failure is terminal.
9. Call save_artifact only after the exact MP4 verifies, passing the step-1 deck specification as markdown_representation.

The workflow permits at most two repairs total: one compile/still repair and one final verification repair.

A render must fit the sandbox operation timeout. The harness controls segment size; do not bypass it. A successful save removes the render work directory; if rendering or verification fails terminally, remove that directory before reporting the failure. For revisions, regenerate from the restored Markdown specification plus the user's instruction, then render and verify a new MP4. Do not edit current.mp4 in place.