Video signal transmitting method, video signal output device, video signal receiver, video anti-duplication control system, additional information superimposing and extracting system and video signal recording medium

An apparatus for detecting additional information superimposed on a signal, said apparatus comprising:

• timing signal generating means for generating a timing signal from information in said signal;
• clock signal generating means for generating a clock signal based on said information in said signal;
• code generating means for generating codes in synchronism with said clock signal and said timing signal;
• extracting means for extracting said additional information from said signal using said codes;
• and
• detecting means for detecting a sync signal in said signal, wherein
• said extracting means extracts said additional information from said signal by generating a code based on said sync signal and using said code to extract said additional information,
• an other code is generated with at least two predetermined timings in advance and delay directions relative to said sync signal,
• a correlation is found between said other code generated with said two timings and said code, and
• a start timing for generating said code is determined based on said correlation.