In-vehicle communication and, more particularly, a controller operating an in-vehicle Ethernet environment and a control method thereof are disclosed. A controller operating in an in-vehicle Ethernet network includes a central processing unit (CPU) and a physical layer (PHY) device connected to the CPU through a first interface, a second interface, and a first pin, wherein the PHY device includes a decoder, the PHY device being configured based on a predetermined configuration value for initialization irrespective of booting of an operating system of the CPU, and the decoder decodes compressed video data received from an external source through the Ethernet network into uncompressed video data and transmits the uncompressed video data to the external source after initialization of the PHY device is completed based on configuration of the first pin.