The invention provides a transmission device, a transmission method, a reception device and reception method. The methods and devices comprises: a video signal transmission unit configured to transmit video signals to an external device via a transmission path with a plurality of channels using a differential signal; a communication unit configured to communicate with said external device via a communication path made up of a pair of differential transmission paths included in said transmission path, wherein the at least one of the pair of the differential transmission paths comprises a function for informing a connection state of an external device by using a DC bias potential; a function information transmission unit configured to transmit first function information indicating that said transmission device includes said communication unit to said external device via a control data line making up said transmission path, wherein the first function information comprises information for indicating whether supporting an audio return channel or an Ethernet channel; and a control unit configured to control each unit.