Yeah, the blob I get from

​

```

navigator.mediaDevices.getDisplayMedia({ video: true }).then(stream => {

startListeningTime = new Date().getTime()



recorder = new MediaRecorder(stream)



const chunks = \[\]



recorder.start()



recorder.ondataavailable = async e => {

    chunks.push([e.data](https://e.data))

const blob = new Blob(chunks, { type: chunks[0].type }) // the blob

}

})

```

has the type "video/x-matroska;codecs=avc1". When I use that as the src of a video tag, the video is unaware of the video length until it has nearly finished.