The intent of this test is to demonstrate subscribing to a broadcast which has its video stream "muted". We have noticed that in Chrome and Safari browsers, when trying to play back a stream that has both Audio and Video tracks, but the Video tracks are empty - because the broadcaster has turned off their Camera - that no playback occurs when assigning the MediaStream source to a <video> element. Presumably, this is because the Video track playback drives the <video> element through its lifecycle events for canplay and loadeddata.
As such, you may require adding an additional <audio> element to the page to allow for the audio to playback while the initial Camera stream is "muted". Playback of a MediaStream with audio flowing and video "muted" is acceptable in said browsers using an <audio> element.
In this test, we listen for the Subscribe.Metadata event and check if the initial streamingMode property on the metadata is set to Audio. In such a case, it means that the broadcaster has muted their video stream. As such, the test starts subscribing to the stream in an audio element to allow for audio playback.
When the streamingMode property changes to Video/Audio, the video stream has become unmuted.
Somethings of note:
- Playback will only work when navigating to this test page after clicking it from the testbed listing.
This is because the autoplay restriction is not enforced since you interacted with the page. If you load this test using a Refresh, the autoplay restriction will be in affect and the audio playback in the audio element will additionally be muted.
- This test does not work so well in Safari
Presumably it is due to having an additional media element (the added audio element) to a page in which another media element already exists and is unmuted and autoplay-ed.