I unpacked firmware of YI4K camera with Irungentoo's unpacker tool, and i found usages of huge number of commands.
One of "t app test MCTF_off 1" I tested on Firmware 1.9.0 it works blurry effect swiched off
One of "t app test MCTF_off 1" I tested on Firmware 1.9.0 it works blurry effect swiched off