A communication system including a transmitter, a receiver, and a TMDS-like link, in which video data and auxiliary data are transmitted from the transmitter to the receiver, or in which video data are transmitted over the link from the transmitter to the receiver and auxiliary data are transmitted from the receiver to the transmitter (or from the transmitter to the receiver and also from receiver to the transmitter), a transmitter or receiver for use in such a system, and methods for sending auxiliary data and video data over such a link, synchronizing such auxiliary data with such video data, and generating clocks having frequency closely matching the rate at which the auxiliary data are transmitted. Typically, the auxiliary data include one or more streams of audio data. In some embodiments the transmitter transmits a video clock to the receiver over a video clock channel, at least one of the transmitter and receiver transmits at least one stream of auxiliary data to the other one of the transmitter and the receiver, and at least one of the transmitter and the receiver transmits over the video clock channel at least one auxiliary clock for the auxiliary data.