It's okay for a sandbox to fall over due to bad inputs and poor memory security if it can just be restarted and move onto other streams.
Thus:
1. Code which processes untrusted input
2. Code written in unsafe languages like C or C++
3. Code that runs without a sandbox
So ffmpeg should be sandboxed, same as the network code and GPU process are sandboxed.
Cheap arse low resource TVs should either include some form of sandboxing OR the entire device should be treated as a "can fall over" sandbox .. well isolated from any household LAN of consequence, etc.
It seems unlikely that BoxStore Brand Android TVs will be well designed with an eye to security so <shrug> they're an exercise for home net admin masochists and/or an opportunity to market sensible easy to use IoT age routers that come preconfigured to handle bad-device(s).