The page is checking what this browser can play
The first answer comes from what the browser reports about itself. The page reads it in about a second, without downloading any video.
The quick set checks HEVC in the common formats and delivery paths, plus H.264, AAC audio and the network.
The waveform is synthetic. It is not patient data.
Playback monitor
The quick set is ready to run.
0:00
Each video test plays here.
Now testing
The trace draws one spike for every video frame the browser shows. A gap means the browser dropped frames.
A flat line means no frames arrived.