137 lines
3.4 KiB
Markdown
137 lines
3.4 KiB
Markdown
---
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name: calculate-metadata
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description: Dynamically set composition duration, dimensions, and props
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metadata:
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tags: calculateMetadata, duration, dimensions, props, dynamic
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---
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# Using calculateMetadata
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Use `calculateMetadata` on a `<Composition>` to dynamically set duration, dimensions, and transform props before rendering.
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Use it when metadata depends on input props, fetched data, or asset metadata.
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For static dimensions, duration, FPS, and initial props, inline the values on `<Composition>` instead.
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```tsx
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<Composition
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id="MyComp"
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component={MyComponent}
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durationInFrames={300}
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fps={30}
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width={1920}
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height={1080}
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defaultProps={{ videoSrc: "https://remotion.media/video.mp4" }}
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calculateMetadata={calculateMetadata}
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/>
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```
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## Setting duration based on a video
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Use the [`getVideoDuration`](../remotion-multimedia/get-video-duration.md) and [`getVideoDimensions`](../remotion-multimedia/get-video-dimensions.md) skills to get the video duration and dimensions:
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```tsx
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import { CalculateMetadataFunction } from "remotion";
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import { getVideoDuration } from "./get-video-duration";
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const calculateMetadata: CalculateMetadataFunction<Props> = async ({
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props,
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}) => {
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const durationInSeconds = await getVideoDuration(props.videoSrc);
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return {
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durationInFrames: Math.ceil(durationInSeconds * 30),
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};
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};
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```
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## Matching dimensions of a video
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Use the [`getVideoDimensions`](../remotion-multimedia/get-video-dimensions.md) skill to get the video dimensions:
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```tsx
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import { CalculateMetadataFunction } from "remotion";
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import { getVideoDuration } from "./get-video-duration";
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import { getVideoDimensions } from "./get-video-dimensions";
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const calculateMetadata: CalculateMetadataFunction<Props> = async ({
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props,
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}) => {
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const dimensions = await getVideoDimensions(props.videoSrc);
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return {
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width: dimensions.width,
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height: dimensions.height,
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};
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};
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```
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## Setting duration based on multiple videos
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```tsx
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const calculateMetadata: CalculateMetadataFunction<Props> = async ({
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props,
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}) => {
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const metadataPromises = props.videos.map((video) =>
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getVideoDuration(video.src),
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);
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const allMetadata = await Promise.all(metadataPromises);
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const totalDuration = allMetadata.reduce(
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(sum, durationInSeconds) => sum + durationInSeconds,
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0,
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);
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return {
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durationInFrames: Math.ceil(totalDuration * 30),
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};
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};
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```
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## Setting a default outName
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Set the default output filename based on props:
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```tsx
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const calculateMetadata: CalculateMetadataFunction<Props> = async ({
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props,
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}) => {
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return {
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defaultOutName: `video-${props.id}`, // .mp4 is added automatically
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};
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};
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```
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## Transforming props
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Fetch data or transform props before rendering:
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```tsx
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const calculateMetadata: CalculateMetadataFunction<Props> = async ({
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props,
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abortSignal,
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}) => {
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const response = await fetch(props.dataUrl, { signal: abortSignal });
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const data = await response.json();
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return {
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props: {
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...props,
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fetchedData: data,
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},
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};
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};
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```
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The `abortSignal` cancels stale requests when props change in the Studio.
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## Return value
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All fields are optional. Returned values override the `<Composition>` props:
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- `durationInFrames`: Number of frames
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- `width`: Composition width in pixels
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- `height`: Composition height in pixels
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- `fps`: Frames per second
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- `props`: Transformed props passed to the component
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- `defaultOutName`: Default output filename
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- `defaultCodec`: Default codec for rendering
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