Do not start streaming or recording before scanning the QR code because the scanner uses the camera to read the code.
Live streaming or recording a video significantly degrades the quality of experience on the device.
To record a video, say "Hey, Cortana" then "Record a video". To download the video, go to the "Mixed Reality Capture" tab in the HoloLens Device Portal.
To conserve the bandwidth and achieve a better streaming stability: