(There are at least a dozen forums this could fit under. I will leave it to the mods to choose the right one.)
I am a Chromecast beginner. I don't use a smartphone and I wasn't impressed with the original dongle so I gave it away. I haven't tried to cast anything since then.
Recently I became interested again, mainly because my Android TV includes a Cast function. There are some HTTP streams we like to watch that can only be accessed by browser. I have a streaming pc set up for this, but even with custom controls it is a hassle to use from the couch. Much simpler is my notebook, which sits next to me.
The Cast function works brilliantly from Chrome, but it is a little different than I remember from the dongle. Previously, the casting device was only needed to establish the initial connection. Once the video and audio started streaming it could be shut off. That now seems to no longer be the case. When I cast from my notebook, the audio switches to the Android TV as it should, but the video operates on both devices. I can switch tabs and use the notebook for other things, but if I put it in standby or close the tab that kills the cast. I can see from my bit rate monitor that data is being downloaded to the notebook then uploaded, presumably to the Android TV. The notebook seems to be used as a conduit. This happens whether I cast a tab or the desktop.
Can anyone explain more about how this works? I don't have a problem with it but would like to know why I am seeing this difference.