fix-webm-duration

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

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

Usage

The library contains only one script fix-webm-duration.js and has no dependencies.

Syntax:

ysFixWebmDuration(blob, duration, callback);

where

blob is Blob object with file contents from MediaRecorder
duration is video duration in milliseconds (you should calculate it while recording the video)
callback is callback function that will receive fixed blob

ysFixWebmDuration will parse and fix your file asynchronously and will call your callback once the result is ready.

If the original blob already contains duration metadata section and the duration value is not empty, the callback will receive it without any changes made.

Example:

var mediaRecorder;
var mediaParts;
var startTime;

function startRecording(stream, options) {
    mediaParts = [];
    mediaRecorder = new MediaRecorder(stream, options);
    mediaRecorder.onstop = function() {
        var duration = Date.now() - startTime;
        var buggyBlob = new Blob(mediaParts, { type: 'video/webm' });
        
        ysFixWebmDuration(buggyBlob, duration, function(fixedBlob) {
            displayResult(fixedBlob);
        });
    };
    mediaRecorder.ondataavailable = function(event) {
        var data = event.data;
        if (data && data.size > 0) {
            mediaParts.push(data);
        }
    };
    mediaRecorder.start();
    startTime = Date.now();
}

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

function displayResult(blob) {
    // ...
}

Note: this example is not a MediaRecorder usage guide.

With webpack

// Type of webmBytes is Uint8Array or ByteBuffer
let webmfile = new WebmFile(webmBytes);
if (webmfile.fixDuration(duration)) {
    let blobWithDuration = webmfile.toBlob();
}

Full example

index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Record and play</title>
</head>

<body>
    <video width="480" height="360" controls id="player" autoplay></video>
    <div><button id="btnrecord">Record</button><button id="btnstop">Stop</button>
    </div>
    <script src="dist/main.js"></script>
</body>

</html>

main.js

import WebmFile from "../../../WebmFile"

(function () {
    let btnRecord = document.querySelector("#btnrecord");
    let btnStop = document.querySelector("#btnstop");
    let player = document.querySelector("#player");

    let videoUrl;
    let recorder;
    let recording = false;
    let recordedBlobs = [];
    let startTime = 0;

    function setRecording(value) {
        recording = value;

        btnStop.disabled = !value;
        btnRecord.disabled = value;
    }

    function ondataavailable_handler(e) {
        recordedBlobs.push(e.data);
    }

    async function recorder_stopHandler(e) {
        let duration = Date.now() - startTime;
        let webmBytes = await (new Blob(recordedBlobs, { type: 'video/webm' })).arrayBuffer();
        let webmfile = new WebmFile(webmBytes);
        if (webmfile.fixDuration(duration)) {
            if (videoUrl) {
                // release the pre url object
                URL.revokeObjectURL(videoUrl);
            }
            videoUrl = player.src = URL.createObjectURL(webmfile.toBlob());
        }
    }

    btnRecord.onclick = async function () {
        recordedBlobs.length = 0;

        let stream = await navigator.mediaDevices.getUserMedia({ video: true, audio: true });
        recorder = new MediaRecorder(stream);
        recorder.ondataavailable = ondataavailable_handler;
        recorder.onstop = recorder_stopHandler;
        recorder.start();
        startTime = Date.now();
        setRecording(true);
    }

    btnStop.onclick = async function () {
        if (recorder) {
            recorder.stop();
            setRecording(false);
            recorder = undefined;
        }
    }

    setRecording(false);
})();

Use webpack to compile the source code

webpack ./main.js

You can also checkout the example here https://plter.github.io/fix-webm-duration/examples/fixduration/

plter / fix-webm-duration Goto Github PK