Download Android KitKat 4.4.2 stock firmware for MyGica ATV582 TV Box from here.
Firmware: Android KitKat 4.4.2 stock
Image file size: 443.1 MB
Platform: Amlogic S805
Build number: 4.4.2
Inside archive: firmware + recovery.img + u-boot.bin
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.