Display a video from a Blob Javascript

Question

I would like to display a video from a Javascript Blob/File object in the HTML5 video tag.

This code only works for small videos :

var reader = new FileReader();
reader.onload = function(e) {
    document.getElementById("video").src=reader.result;
 }
reader.readAsDataURL(vid);

I cannot use this for big videos (> 10MB). Is there a solution to display a big video from a blob object in HTML 5?

Solution 1

I've found. It was so simple that I didnt even see it...

/**
 * @param {Blob} videoFile
 * @param {HTMLVideoElement} videoEl 
 * @returns {void}
 */
function display( videoFile, videoEl ) {

    // Preconditions:
    if( !( videoFile instanceof Blob ) ) throw new Error( '`videoFile` must be a Blob or File object.' ); // The `File` prototype extends the `Blob` prototype, so `instanceof Blob` works for both.
    if( !( videoEl instanceof HTMLVideoElement ) ) throw new Error( '`videoEl` must be a <video> element.' );
    
    // 

    const newObjectUrl = URL.createObjectURL( videoFile );
        
    // URLs created by `URL.createObjectURL` always use the `blob:` URI scheme: https://w3c.github.io/FileAPI/#dfn-createObjectURL
    const oldObjectUrl = videoEl.currentSrc;
    if( oldObjectUrl && oldObjectUrl.startsWith('blob:') ) {
        // It is very important to revoke the previous ObjectURL to prevent memory leaks. Un-set the `src` first.
        // See https://developer.mozilla.org/en-US/docs/Web/API/URL/createObjectURL

        videoEl.src = ''; // <-- Un-set the src property *before* revoking the object URL.
        URL.revokeObjectURL( oldObjectUrl );
    }

    // Then set the new URL:
    videoEl.src = newObjectUrl;

    // And load it:
    videoEl.load(); // https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/load
    
}

Solution 2

In some case blobObject.data should be provided in createObjectURL() method. See this simple trick:

function playVideo(videoStream){ // as blob 

 var video = document.querySelector('video');

 var videoUrl=window.URL.createObjectURL(videoStream.data);// blob.data gives actual data

 video.src = videoUrl;
}

Comments

[Jan Hančič]

Can you provide more info on what the issue is?

[Antonin M.]

For example, Chrome and Firefox shutdown when they tried to read a 15 MB video. I think that it's due to the video size. Browsers cannot read and display a 15MB string in the HTML code.

[Hubert Grzeskowiak]

What type is the vid parameter?

[Antonin M.]

@HubertGrzeskowiak it is a Blob or File object

[Satys]

Is it only me who is still struggling with it? Sorry, not working for me.

[Dai]

@Satys I've updated this answer to make things more clearer, I hope it helps.

[Dai]

The Blob type does not have a property named data, so your videoStream object is not actually Blob but some other type. See developer.mozilla.org/en-US/docs/Web/API/Blob