Support the user is following a video feed, but is mainly listening to the audio. Only once in a while the user would like to 'unmute' the video and experience both video and audio. For the rest of the time, the user can mute the video and experience only the audio part of the stream.
Could the HD icon in the video player get the same behavior as the audio icon? In terms of hovering, nothing has to be changed, this is already similar. Upon clicking on the HD icon, could the video get disabled and enabled again?
Implementing this would allow users to use less processing power as the video of the feed can be muted while the audio continues.
Additionally, the provider of the video feed could also offers an audio-only feed to which is switched to and from by this video mute behavior. This will also save bandwidth for provider and user.