A control apparatus (100; 700; 1300) comprising: a selecting unit configured to select one of external apparatuses (101, 102); a sending unit configured to send an HPD (Hot Plug Detect) signal from the control apparatus to the selected external apparatus via an HPD line (126, 131); a receiving unit configured to receive video data, audio data, or both video and audio data from the selected external apparatus via a TMDS (Transition Minimized Differential Signaling) line (128, 133); and a control unit (118; 701) configured to: determine a device type of the selected external apparatus, based on information indicating the device type of the selected external apparatus that is received from the selected external apparatus; determine whether or not the selected external apparatus is an apparatus for which a predetermined process corresponding to HDCP (High-bandwidth Digital Content Protection) standard is to be executed, based on the device type of the selected external apparatus; allow to perform a process of changing a state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is to be executed; and avoid performing the process of changing the state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is not to be executed, wherein the predetermined process includes a process for protecting data received by the receiving unit from the selected external apparatus via the TMDS line. a selecting unit configured to select one of external apparatuses (101, 102); a sending unit configured to send an HPD (Hot Plug Detect) signal from the control apparatus to the selected external apparatus via an HPD line (126, 131); a receiving unit configured to receive video data, audio data, or both video and audio data from the selected external apparatus via a TMDS (Transition Minimized Differential Signaling) line (128, 133); and a control unit (118; 701) configured to: determine a device type of the selected external apparatus, based on information indicating the device type of the selected external apparatus that is received from the selected external apparatus; determine whether or not the selected external apparatus is an apparatus for which a predetermined process corresponding to HDCP (High-bandwidth Digital Content Protection) standard is to be executed, based on the device type of the selected external apparatus; allow to perform a process of changing a state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is to be executed; and avoid performing the process of changing the state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is not to be executed, determine a device type of the selected external apparatus, based on information indicating the device type of the selected external apparatus that is received from the selected external apparatus; determine whether or not the selected external apparatus is an apparatus for which a predetermined process corresponding to HDCP (High-bandwidth Digital Content Protection) standard is to be executed, based on the device type of the selected external apparatus; allow to perform a process of changing a state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is to be executed; and avoid performing the process of changing the state of the HPD signal if the selected external apparatus is an apparatus for which the predetermined process is not to be executed, wherein the predetermined process includes a process for protecting data received by the receiving unit from the selected external apparatus via the TMDS line.