1. An apparatus for performing overlap filter and core transform, comprising: a first select multiplexer, for receiving multi-port input data; a transform operation module array, connected to the first select multiplexer, for receiving multi-port output of the first select multiplexer; a second select multiplexer, connected to the transform operation module array, for receiving output of multi-port operation results of the transform operation module array and the multi-port input data; a register array, comprising a plurality of registers, connected to the second select multiplexer, for receiving multi-port output of the second select multiplexer, and temporarily storing the received data in parts of the registers, wherein the first select multiplexer and the second select multiplexer are both used for reading values stored in the registers of the register array; and a control signal generator, generating a plurality of control signals according to a schedule of the overlap filter and the core transform, so as to control the first select multiplexer, the transform operation module array, the second select multiplexer, and the register array, wherein the control signal generator controls the first select multiplexer to select the multi-port input data and the values stored in the parts of the registers and to apply the selected data to the transform operation module array, wherein the control signal generator controls the second select multiplexer to select the multi-port input data, the multi-port operation results output by the transform operation module array, and the values stored in the parts of the registers, and to apply the selected data to the registers to be stored accordingly.