A system on chip includes: a codec encoding image frames; and a codec controller sending the image frames to the codec and allocating a buffer for encoding the image frames. The codec controller sends a first image frame to the codec. The codec controller allocates the first buffer to a memory and sends the first image frame to the codec. The codec encodes the first image frame and sends the encoded first image frame to the codec controller. The codec controller allocates the first buffer to the memory and sends a second image frame to the codec. The codec requests the codec controller to allocate a second buffer of a second size. The codec controller allocates the second buffer to the memory and sends the second image frame to the codec, and the codec encodes the second image frame and sends the encoded second image frame to the codec controller.