title: Can't play HTML5 Video with Blob source on iOS devices
body: <p>I have a React web app that gets the video URL from a server, then requests the video as a blob and tries to play this on an HTML video tag. I'm doing this because the client sometimes has issues with the internet and videos can stutter while playing, they'd rather wait longer for the video to load and then play it smoothly than have a choppy video. (I'm also saving the blob to IndexedDB as cache, but that's not related to the issue I'm having now, I'm just adding this as context but it has been disabled while I try to figure out this iOS problem)</p>
  <p>I have a function to download the video, which then returns the Blob and a URL created from that blob object.</p>
  <pre><code>async function downloadVideo(videoUrl) {
    return new Promise(function(resolve, reject) {
      var req = new XMLHttpRequest();
      req.open('GET', videoUrl, true);
      req.responseType = 'blob';
  
      req.onload = function() {
        // Onload is triggered even on 404
        // so we need to check the status code
        if (this.status === 200) {
          var videoBlob = new Blob([this.response], { type: 'video/mp4' });
          console.log('Video blob?', videoBlob);
          var vid = { objBlob: videoBlob, vidURL: URL.createObjectURL(videoBlob) };
          // Video is now downloaded and converted into ObjectURL
          resolve(vid);
        } else {
          reject('Video download failed with status ', this.status);
        }
      };
      req.onerror = function() {
        reject('Unable to Download Video');
      };
  
      req.send();
    });
  } 
  </code></pre>
  <p>And then I have the element that plays the blob video:</p>
  <pre><code>&lt;video
      muted={true}
      autoPlay={true}
      loop={false}
      onError={err =&gt; {
        alert('Video load error. ' + err.target.error.iosMessage);
      }}
      src={downloadedVideo.url}
  /&gt;
  </code></pre>
  <p>That <code>downloadedVideo.url</code> is the blob object URL created on the DownloadVideo function</p>
  <p>All of this works fine on desktop (Linux) and on Android, but the video doesn't play from the Blob on iOS devices. I've tried Safari, Chrome, and Firefox and the problem is the same.
  on iOS I can get the video Blob and create an URL from it, but when I pass it as src it doesn't work, all I can get from the error (a MediaError object) is the code, 4, but the message is undefined.</p>
  <p>If instead of the blob I pass the original video URL as src, it works on all devices, but then I can't cache the video and this feature will have to be dropped.</p>
  <p>I've tried several videos and made sure encoding was compatible with iOS.</p>
  <p>I could not find anything stating that iOS is not compatible with Blob URLs for video, so this should work, but I can't figure out why it doesn't.</p>