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SmartYouTubeTV: A YouTube client for set-top boxes and Android-based TVs:
NOTE: SmartYouTubeTV provides internal login mechanism which allows you to keep content up to date in a very convenient way.
Easy installation in less than 5 minutes with only the FireTV
Standard installation via ADB
How to change system language with only the MiTV3
The device/resolution options at start launches different playing methods (as per https://github.com/yuliskov/SmartTubeLegacy/issues/15#issuecomment-364805950)
Also important, it's possible to select max resolution and codec (ie 1080/AVC1) via the start screen that will be applied on video loading (Codec option).
The Remember tick box acts as a configuration saving for next app launches.