Video display device and cooperative control method in video display device

A television comprising:

• a tuner configured to receive a digital broadcast signal;
• a High-Definition Multimedia Interface (HDMI) interface configured to receive a video from an external device and communicate with the external device;
• a display configured to display the video received from the external device;
• a wireless LAN interface configured to communicate with a smartphone being in association with the external device;
• a memory configured to store information about the association;
• and
• a processor,
• the processor being configured to, when detecting information showing that the external device is connected to the television, or information showing that the external device is turned on, by communication via the HDMI interface,
• generate a start signal for initiating an application software on the smartphone so as to cause the application software to display, on a display of the smartphone, an operation screen for accepting an operation instruction to the external device;
• and
• transmit the start signal to the smartphone via the wireless LAN interface, and
• the video received by the HDMI interface from the external device being controlled based on the operation instruction accepted by the operation screen which has been displayed on the display of the smartphone.