The high-definition multimedia interface (HDMI) unit includes a source interface module, configured to communicate with a sink device, a sink interface module, configured to communicate with a source device, an interface circuit module, configured to connect to an HDMI interface of an external device, a processing module, configured to identify a device type of the connected external device, and control a switching circuit module, and the switching circuit module, configured to establish a connection between the HDMI interface of the external device connected to the interface circuit module and the source interface module or the sink interface module. It is implemented that when a different type of a device connected to a multimedia terminal matches a port, it is ensured that the multimedia terminal establishes a connection to a source device or a sink device.