webm-fix-duration

A fork of fix-webm-duration, adding TypeScript and Promise support.

navigator.mediaDevices.getUserMedia + MediaRecorder create WEBM files without duration metadata.

This library appends missing metadata section right to the file blob.

Usage

The library exports a webmFixDuration function of the following signature:

``ts
function webmFixDuration(
blob: Blob,
duration: number,
type = 'video/webm'
): Promise;
`

with:

- blob: Blob being the output from MediaRecorder,
- duration: number being duration in milliseconds,

and returning a Promise, which will be resolved with a Blob object with fixed duration.

If duration is already present, the function will return an unmodified Blob.

Example

`ts
import { webmFixDuration } from 'webm-fix-duration';

let mediaRecorder: MediaRecorder | undefined;
let mediaParts: Blob = [];
let startTime: number = 0;

function startRecording(stream: MediaStream, options: any) {
mediaParts = [];
mediaRecorder = new MediaRecorder(stream, options);
mediaRecorder.onstop = async () => {
const duration = Date.now() - startTime;
const buggyBlob = new Blob(mediaParts, { type: 'video/webm' });

const fixedBlob = await webmFixDuration(buggyBlob, duration);
displayResult(fixedBlob);
};
mediaRecorder.ondataavailable = event => {
const data = event.data;
if (data && data.size > 0) {
mediaParts.push(data);
}
};
mediaRecorder.start();
startTime = Date.now();
}

function stopRecording() {
mediaRecorder.stop();
}

function displayResult(blob: Blob) {
// ...
}
`

Note: this example is not a MediaRecorder` usage guide.