remotion-best-practices

## When to use

Use this skills whenever you are dealing with Remotion code to obtain the domain-specific knowledge.

## New project setup

When in an empty folder or workspace with no existing Remotion project, scaffold one using:

```bash
npx create-video@latest --yes --blank --no-tailwind my-video
```

Replace `my-video` with a suitable project name.

## Designing a video

Animate properties using `useCurrentFrame()` and `interpolate()`. Use Easing to customize the timing of the animation.

```tsx
import { useCurrentFrame, Easing } from "remotion";

export const FadeIn = () => {
  const frame = useCurrentFrame();
  const { fps } = useVideoConfig();

  const opacity = interpolate(frame, [0, 2 * fps], [0, 1], {
    extrapolateRight: "clamp",
    extrapolateLeft: "clamp",
    easing: Easing.bezier(0.16, 1, 0.3, 1),
  });

  return <div style={{ opacity }}>Hello World!</div>;
};
```

CSS transitions or animations are FORBIDDEN - they will not render correctly.  
Tailwind animation class names are FORBIDDEN - they will not render correctly.

Place assets in the `public/` folder at your project root.

Use `staticFile()` to reference files from the `public/` folder.

Add images using the `<Img>` component:

```tsx
import { Img, staticFile } from "remotion";

export const MyComposition = () => {
  return <Img src={staticFile("logo.png")} style={{ width: 100, height: 100 }} />;
};
```

Add videos using the `<Video>` component from `@remotion/media`:

```tsx
import { Video } from "@remotion/media";
import { staticFile } from "remotion";

export const MyComposition = () => {
  return <Video src={staticFile("video.mp4")} style={{ opacity: 0.5 }} />;
};
```

Add audio using the `<Audio>` component from `@remotion/media`:

```tsx
import { Audio } from "@remotion/media";
import { staticFile } from "remotion";

export const MyComposition = () => {
  return <Audio src={staticFile("audio.mp3")} />;
};
```

Assets can be also referenced as remote URLs:

```tsx
import { Video } from "@remotion/media";

export const MyComposition = () => {
  return <Video src="https://remotion.media/video.mp4" />
};
```

To delay content wrap it in `<Sequence>` and use `from`.
To limit the duration of an element, use `durationInFrames` of `<Sequence>`.
`<Sequence>` by default is an absolute fill. For inline content, use `layout="none"`.

```tsx
import { Sequence } from "remotion";

export const Title = () => {
  const frame = useCurrentFrame();
  const { fps } = useVideoConfig();

  const opacity = interpolate(frame, [0, 2 * fps], [0, 1], {
    extrapolateRight: "clamp",
    extrapolateLeft: "clamp",
    easing: Easing.bezier(0.16, 1, 0.3, 1),
  });

  return <div style={{ opacity }}>Title</div>;
};

export const Subtitle = () => {
  return <div>Subtitle</div>;
};

const Main = () => {
  const {fps} = useVideoConfig();

  return (
    <AbsoluteFill>
      <Sequence>
        <Background />
      </Sequence>
      <Sequence from={1 * fps} durationInFrames={2 * fps} layout="none">
        <Title />
      </Sequence>
      <Sequence from={2 * fps} durationInFrames={2 * fps} layout="none">
        <Subtitle />
      </Sequence>
    </AbsoluteFill>
  );
}
```

The width, height, fps, and duration of a video is defined in `src/Root.tsx`:

```tsx
import { Composition } from "remotion";
import { MyComposition } from "./MyComposition";

export const RemotionRoot = () => {
  return (
    <Composition
      id="MyComposition"
      component={MyComposition}
      durationInFrames={100}
      fps={30}
      width={1080}
      height={1080}
    />
  );
};
```

Metadata can also be calculated dynamically:

```tsx
import { Composition, CalculateMetadataFunction } from "remotion";
import { MyComposition, MyCompositionProps } from "./MyComposition";

const calculateMetadata: CalculateMetadataFunction<
  MyCompositionProps
> = async ({ props, abortSignal }) => {
  const data = await fetch(`https://api.example.com/video/${props.videoId}`, {
    signal: abortSignal,
  }).then((res) => res.json());

  return {
    durationInFrames: Math.ceil(data.duration * 30),
    props: {
      ...props,
      videoUrl: data.url,
    },
    width: 1080,
    height: 1080,
  };
};

export const RemotionRoot = () => {
  return (
    <Composition
      id="MyComposition"
      component={MyComposition}
      fps={30}
      width={1080}
      height={1080}
      defaultProps={{ videoId: "abc123" }}
      calculateMetadata={calculateMetadata}
    />
  );
};
```

## Starting preview

Start the Remotion Studio to preview a video:

```bash
npx remotion studio
```

## Optional: one-frame render check

You can render a single frame with the CLI to sanity-check layout, colors, or timing.  
Skip it for trivial edits, pure refactors, or when you already have enough confidence from Studio or prior renders.

```bash
npx remotion still [composition-id] --scale=0.25 --frame=30
```

At 30 fps, `--frame=30` is the one-second mark (`--frame` is zero-based).

## Captions

When dealing with captions or subtitles, load the [./rules/subtitles.md](./rules/subtitles.md) file for more information.

## Using FFmpeg

For some video operations, such as trimming videos or detecting silence, FFmpeg should be used. Load the [./rules/ffmpeg.md](./rules/ffmpeg.md) file for more information.

## Silence detection

When needing to detect and trim silent segments from video or audio files, load the [./rules/silence-detection.md](./rules/silence-detection.md) file.

## Audio visualization

When needing to visualize audio (spectrum bars, waveforms, bass-reactive effects), load the [./rules/audio-visualization.md](./rules/audio-visualization.md) file for more information.

## Sound effects

When needing to use sound effects, load the [./rules/sfx.md](./rules/sfx.md) file for more information.

## 3D content

See [rules/3d.md](rules/3d.md) for 3D content in Remotion using Three.js and React Three Fiber.

## Advanced audio

See [rules/audio.md](rules/audio.md) for advanced audio features like trimmi