Just mentioning this for other Mi Box 3 owners that read about videocalling not working on the Mi Box 3. It actually works great!
Every thread and forum mentions that it does not work. Some threads state that the webcam drivers are missing, this luckely isn't true for every webcam. It looks like that at least the webcams using a standard linux webcam driver (UVC, USB video device class) are working out of the box. Brands like logitech mention this on their product page.
Both me and my parents have a Mi Box 3 and they had a few Webcams lying around to videocall their grandkids on a desktop(completly forgetting about their kids I might add). Every webcam they had worked great on the Mi box 3 (using the official firmware).
We connected the webcam while the device was on, started tellybean, noticed it didn't reconize the camera, rebooted the mibox (by holding down the standby button), again started tellybean and noticed it did reconize the webcam (the option to test your camera is now visible). All the cams are from the brand logitech and the oldest we tried was the logitech 9000 pro. Newer ones from this year with 1080p/30fps also worked fine. Especially the last one with glassoptics and stereo mics offered crisp video in a dimlighted surrounding and recieved every sound like you where sitting in from of each other (to be fair the 9000 pro did also great untill we only lighted the livingroom with one lightbulb which resulted in a grained VHS like video).
We used several apps, but I would recommend to start with tellybean since that one is available from the playstore and automatically updates (sideloading isn't great when you don't live near your parents).
p.s. I did ran into a trouble when the mibox 3 hanged on starting the videocall. Resetting to factorysettings and reinstalling all the apps solved that for me and never happed again. I asumed it was a issue due to removing my account from the box and adding the one from my parents.
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