A transmission efficient packet based display interface arranged to couple a multimedia source device to a multimedia sink device is disclosed. The transmission efficient interface includes a bi-directional auxiliary channel arranged to transfer information between the multimedia source device and the multimedia sink device and vice versa, wherein the information transferred over the auxiliary channel includes a set of packet attributes. The interface also includes a unidirectional main link arranged to carry a number multimedia data packets from the transmitter unit to the receiver unit each having a multimedia data packet header. In the described embodiment, each of the headers is substantially reduced in size over what would otherwise be necessary since the packet attributes are communicated via the auxiliary channel prior to the transmission of the main link packets over main link thereby minimizing the packet overhead and providing a very high main link efficiency.