Patent ID: 7245664

Claim:
A method of controlling a system for transmitting data-compressed coded digital video signals in a packet form from a transmission portion to a reception portion through a signal line, comprising the steps of: in said transmission portion: switching selectively any one of a plurality of video signals having mutually asynchronous phases, converting the selected video signal to a data-compressed coded digital video signal, converting said data-compressed coded digital video signals to a signal stream as a sequence of a plurality of packets each containing a predetermined sync code and a payload, and transmitting said signal stream from said transmission portion, and when a failure of periodicity of the digital video signal is detected prior to the step of converting said digital video signal to the data-compressed coded digital video signal, transmitting a signal stream containing a packet having a dummy signal, that is not said sync code, inserted into a position of said sync code in a packet to be transmitted at that time, when a failure of periodicity of said video signals is detected; and in said reception portion, when said reception portion does not detect said predetermined sync code in a predetermined period from the signal stream received from said transmission portion, stopping image reproduction process on the packet containing said dummy signal inserted in a position of said sync code in the received signal stream, and executing an image reproduction process based on a predetermined normal video signal data not depending on said packet containing said dummy signal received in said reception portion.