To provide a transmitter for efficiently transmitting data and smoothly reproducing data without any break halfway, and to provide a receiver and a communication system.

The transmitter has a detecting part 141 for detecting a value of a prescribed parameter from data to be transmitted, an acquisition part 142 for calculating the magnitude of a gradient with respect to a reproduction time of data to be transmitted in the parameter detected by the detecting part 141 and acquiring timing when the magnitude of the gradient exceeds a prescribed threshold, transmission preprocessing parts 143,144 for performing processing for reducing the capacity of the data to be transmitted from the timing acquired by the acquiring part 142 to the next timing to be acquired by the acquiring part 142, and a transmitting part 121 for transmitting the data to be transmitted, to which the processing is performed by the transmission preprocessing parts 143,144.