A video signal processing method that is performed by a video signal processing device that includes a first signal processor and a second signal processor, the first signal processor receiving input of a plurality of video signals, each including a plurality of packets, and multiplexing the plurality of video signals to output a multiplexed video signal via a single output system, and the second signal processor receiving input of the multiplexed video signal and demultiplexing the multiplexed video signal to output the plurality of video signals,
- the video signal processing method comprising:
- changing, by an instruction from a user of the video signal processing device via an input receiver, a channel that carries any video signal out of the plurality of video signals and is to be used as the input of the first signal processor,
- transmitting, by the first signal processor, a notification for starting detection processing for detecting deficient data whose size is less than a size of one packet with respect to the video signal of which channel is changed, to the second signal processor, the transmitting the notification being caused by changing the channel,
- starting, by the second signal processor, the detection processing upon receiving the notification, and
- when the deficient data is detected in the video signal of which channel is changed, performing, by the second signal processor, one of (i) processing for discarding the deficient data detected and (ii) processing for adding dummy data to the deficient data detected to make a size of the deficient data equal to a size of an integral multiple of one packet, the integral multiple being a multiple of an integer of 1 or greater.