To the uninitiated, a TV firmware file is a black box. It bundles the bootloader, the Linux kernel, the Android system files, and the vendor's user interface into one giant, encrypted blob. Normal programs couldn't read it. Leo typed the command to the image.
img2simg system_ext4.img system.img
Some MStar TVs require an RSA signature verification. If the device has an unlocked bootloader, this step is ignored. If locked, the repacked image must be signed with the manufacturer's private key (usually unavailable) or the verification checks must be patched out of the bootloader (advanced exploitation). mstar android tv firmware tools repack