Practical speaker connection is identified using a device having a sound channel of a 5.1 channel or 7.1 channel, and a device is provided that can easily reproduce the optimum multiple channels. Actual speaker arrangement can be identified by, for example, measuring the impedance of a terminal at the side of an audio amplifier. If incorrect connection is found, a warning is issued. This information is transmitted to a signal source with an EDID and a signal with the optimum a number of sound channel is sent. The EDID is also used for the connection with a display unit and the speaker connection with which the display unit is provided uniquely. For example, a sound through the 7.1 channel is easily reproduced using the speaker of the display unit in the channel of the front speaker.