A signal processing device is disclosed, which includes a plurality of channel receivers, a plurality of time code processors in one-to-one correspondence with the channel receivers, a timing generator, a signal processor and a transmitter, wherein each channel receiver is configured to parse an audio-video signal which has a data format defined by the SDI protocol and including a time code that characterizes time information. Each time code processor is configured to extract the time code from a parsed audio-video signal obtained by a corresponding channel receiver, and form first frame image data including a frame time code. The signal processor is configured to form an absolute frame output image based on multiple channels of the first frame of image data, frame time codes therein, and an internal clock signal generated by the timing generator. The transmitter is configured to transmit the absolute frame output image for display.