How to connect the TV box to the Android OS devices?

Android OS head unit is similar to a Windows computer. If you want to connect any device (except via Bluetooth or WIFI) to an Android OS head unit is similar to installing a printer on a computer, you need to install (or built-in) a driver at OS, not only just connect CVBS and then it will be working well.
More explanation. if you want to install a printer on a computer, you need to install a printer driver first, not only see the printer has a USB connector, then think it will be working.
The same, you can not think your Android OS head unit has CVBS input, then think it will be working well if you connect an unverified CVBS output digital TV box.
So you should first upgrade the Android OS firmware (built-in driver of different suppliers’ digital TV boxes) to solve this problem. So please contact your Android OS firmware supplier, who will give you the technology support.