How can I save a video recorded using MediaRecorder to a file in Asp.NET Core?

Question

By the way, please don't post links to other similar questions because I have seen them all and they don't help. I've been working on this for 7 hours.

So, I'm trying to capture a video from a webcam (using MediaRecorder) and save it to a file (in wwwroot or database) via a controller. I have the video capture part working, but I'm not sure how to turn the recorded blobs into a file or a writeable object.

Here's how it works. I use this script for recording. This is from a demo and it works perfectly, except for the fact that it only has an option to download. The part of the script responsible for download is commented out, and underneath that is the part I implemented to try and upload this video and save it in a folder.

const mediaSource = new MediaSource();
mediaSource.addEventListener('sourceopen', handleSourceOpen, false);
let mediaRecorder;
let recordedBlobs;
let sourceBuffer;

const errorMsgElement = document.querySelector('span#errorMsg');
const recordedVideo = document.querySelector('video#recorded');
const recordButton = document.querySelector('button#record');
recordButton.addEventListener('click', () => {
    if (recordButton.textContent === 'Start Recording') {
        startRecording();
    } else {
        stopRecording();
        recordButton.textContent = 'Start Recording';
        playButton.disabled = false;
        downloadButton.disabled = false;
    }
});

const playButton = document.querySelector('button#play');
playButton.addEventListener('click', () => {
    const superBuffer = new Blob(recordedBlobs, { type: 'video/webm' });
    recordedVideo.src = null;
    recordedVideo.srcObject = null;
    recordedVideo.src = window.URL.createObjectURL(superBuffer);
    recordedVideo.controls = true;
    recordedVideo.play();
});

const downloadButton = document.querySelector('button#download');
downloadButton.addEventListener('click', () => {
    const blob = new Blob(recordedBlobs, { type: 'video/webm' });
    const url = window.URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.style.display = 'none';
    a.href = url;
    a.download = 'test.webm';
    document.body.appendChild(a);
    a.click();
    setTimeout(() => {
        document.body.removeChild(a);
        window.URL.revokeObjectURL(url);
    }, 100);
});

downloadButton.addEventListener('click', () => {
    var formData = new FormData();
    formData.append('video-filename', fileName);
    formData.append('video-blob', recordedBlobs);
    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/page/upload');
    xhr.send(formData);
});

function handleSourceOpen(event) {
    console.log('MediaSource opened');
    sourceBuffer = mediaSource.addSourceBuffer('video/webm; codecs="vp8"');
    console.log('Source buffer: ', sourceBuffer);
}

function handleDataAvailable(event) {
    console.log('handleDataAvailable', event);
    if (event.data && event.data.size > 0) {
        recordedBlobs.push(event.data);
    }
}

function startRecording() {
    recordedBlobs = [];
    let options = { mimeType: 'video/webm;codecs=vp9' };
    if (!MediaRecorder.isTypeSupported(options.mimeType)) {
        console.error(`${options.mimeType} is not Supported`);
        errorMsgElement.innerHTML = `${options.mimeType} is not Supported`;
        options = { mimeType: 'video/webm;codecs=vp8' };
        if (!MediaRecorder.isTypeSupported(options.mimeType)) {
            console.error(`${options.mimeType} is not Supported`);
            errorMsgElement.innerHTML = `${options.mimeType} is not Supported`;
            options = { mimeType: 'video/webm' };
            if (!MediaRecorder.isTypeSupported(options.mimeType)) {
                console.error(`${options.mimeType} is not Supported`);
                errorMsgElement.innerHTML = `${options.mimeType} is not Supported`;
                options = { mimeType: '' };
            }
        }
    }

    try {
        mediaRecorder = new MediaRecorder(window.stream, options);
    } catch (e) {
        console.error('Exception while creating MediaRecorder:', e);
        errorMsgElement.innerHTML = `Exception while creating MediaRecorder: ${JSON.stringify(e)}`;
        return;
    }

    console.log('Created MediaRecorder', mediaRecorder, 'with options', options);
    recordButton.textContent = 'Stop Recording';
    playButton.disabled = true;
    downloadButton.disabled = true;
    mediaRecorder.onstop = (event) => {
        console.log('Recorder stopped: ', event);
        console.log('Recorded Blobs: ', recordedBlobs);
    };
    mediaRecorder.ondataavailable = handleDataAvailable;
    mediaRecorder.start(10); // collect 10ms of data
    console.log('MediaRecorder started', mediaRecorder);
}

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

function handleSuccess(stream) {
    recordButton.disabled = false;
    console.log('getUserMedia() got stream:', stream);
    window.stream = stream;

    const gumVideo = document.querySelector('video#gum');
    gumVideo.srcObject = stream;
}

async function init(constraints) {
    try {
        const stream = await navigator.mediaDevices.getUserMedia(constraints);
        handleSuccess(stream);
    } catch (e) {
        console.error('navigator.getUserMedia error:', e);
        errorMsgElement.innerHTML = `navigator.getUserMedia error:${e.toString()}`;
    }
}

document.querySelector('button#start').addEventListener('click', async () => {
    const hasEchoCancellation = false;
    const constraints = {
        audio: {
            echoCancellation: { exact: hasEchoCancellation }
        },
        video: {
            width: 1280, height: 720
        }
    };
    console.log('Using media constraints:', constraints);
    await init(constraints);
});

This is the original part:

const downloadButton = document.querySelector('button#download');
//downloadButton.addEventListener('click', () => {
//    const blob = new Blob(recordedBlobs, { type: 'video/webm' });
//    const url = window.URL.createObjectURL(blob);
//    const a = document.createElement('a');
//    a.style.display = 'none';
//    a.href = url;
//    a.download = 'test.webm';
//    document.body.appendChild(a);
//    a.click();
//    setTimeout(() => {
//        document.body.removeChild(a);
//        window.URL.revokeObjectURL(url);
//    }, 100);
//});

and my attempt:

downloadButton.addEventListener('click', () => {
    var formData = new FormData();
    formData.append('video-filename', fileName);
    formData.append('video-blob', recordedBlobs);
    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/page/upload');
    xhr.send(formData);
});

This sends the recorder blobs (which is, apparently, how these videos are stored) to the controller which looks like this at this time:

[HttpPost]
public async Task<IActionResult> Upload()
{
    var form = Request.Form;
    var fileName = form["video-filename"];
    Debug.WriteLine(form.ToString());
    Debug.WriteLine(form["video-filename"]);
    Debug.WriteLine(form["video-blob"].ToString());

    //var filePath = Path.Combine(Directory.GetCurrentDirectory(), @"wwwroot\videos", fileName);
    //using (var fileStream = new FileStream(filePath, FileMode.Create))
    //{
    //    await form.CopyToAsync(fileStream);
    //}
    return View("Upload");
}

I can access the fileName and the array of blobs, but I have no idea what to do to save it to a file. Your help will be greatly appreciated.

Do have a look at this. https://stackoverflow.com/questions/19455347/save-byte-array-to-file. — Deep Dhillon, Apr 24 '20 at 16:22

Shahmir Alam · Answer 1 · 2020-07-30T01:22:29.713

you can make a ajax post request to some server url and save that video file into the server directory.

    this.blob = new Blob(this.blobs, { type: 'video/mp4' });
    var videoObj = new File([this.blob], "recording.mp4");
 
    var client = new Vimeo(CLIENT_ID, CLIENT_SECRET, ACCESS_TOKEN);
     var params = {
      'name': 'Vimeo API SDK test upload',
      'description': "This video was uploaded through the Vimeo API's NodeJS SDK."
    }

// making axios post request to php server to save this video
 axios.post('https://your_server_url.com/host.php', videoObj)
       .then(res => {
         console.log('upload done ')
         console.log(res.data.url)
       })

// here i am uploading video to vimeo 
   

 client.upload(
      videoObj,
      params,
      function (uri) {
        console.log('File upload completed. Your Vimeo URI is:', uri)
      },
      function (bytesUploaded, bytesTotal) {
        var percentage = (bytesUploaded / bytesTotal * 100).toFixed(2)
        console.log(bytesUploaded, bytesTotal, percentage + '%')
      },
      function (error) {
        console.log('Failed because: ' + error)
      }
    )

php code to handle the file and save file

<?php   
set_time_limit(0);
header('Content-Type: application/json; charset=utf-8');    
header("Access-Control-Allow-Origin: *");   
header("Access-Control-Allow-Methods: PUT, GET, POST"); 



$response = array();    
$upload_dir = 'recordings/';    
$server_url = 'https://your_server_url';    

if($_FILES['video'])    
{   
    $video_name = $_FILES["video"]["name"]; 
    $video_tmp_name = $_FILES["video"]["tmp_name"]; 
    $orig_file_size = filesize($video_tmp_name);
    $error = $_FILES["video"]["error"]; 

    if($error > 0){ 
        $response = array(  
            "status" => "error",    
            "error" => true,    
            "message" => "Error uploading the file 1!",
            "detail"=>  $_FILES["video"]["error"],
        );  
    }else   
    {
    $target_file = 'recordings/'. $_FILES['video']['name'];
    $chunk_size = 256; // chunk in bytes
        $upload_start = 0;
        $random_name = rand(1000,1000000)."-".$video_name;  
        $upload_name = $upload_dir.strtolower($random_name);    
        $upload_name = preg_replace('/\s+/', '-', $upload_name);    
    
    $handle = fopen($video_tmp_name, "rb");
        $fp = fopen($upload_name, 'w');
        while($upload_start < $orig_file_size) {
 
        $contents = fread($handle, $chunk_size);
        fwrite($fp, $contents);
 
        $upload_start += strlen($contents);
        fseek($handle, $upload_start);
    }
 
    fclose($handle);
    fclose($fp);
    unlink($_FILES['video']['tmp_name']);
 
    //echo "File uploaded successfully.";
     $response = array(
                "status" => "success",
                "error" => false,
                "message" => "File uploaded successfully",
                "url" => $server_url."/".$upload_name
              );

      



    }

}else{  
    $response = array(  
        "status" => "error",    
        "error" => true,    
        "message" => "No file was sent!"    
    );  
}   

echo json_encode($response);    
?>

NOTE this wil work for small files. if you want to send large files you have to send data in chunks also from the client side. you can use resumable.js or WebSockets

could you try to explain your code a little, not just post plain code-sample — Homungus, Jul 28 '20 at 12:46

How can I save a video recorded using MediaRecorder to a file in Asp.NET Core?

1 Answers1