a compression and expansion system for a composite video signal comprises an extracting circuit for judging maximum and minimum points in a video signal of a composite video signal , to extract these maximum and minimum points , a digital value obtaining circuit for obtaining digital values of levels of the extracted points and digital values of positions of the extracted points in the video signal , to record and reproduce or transmit these digital values thus obtained , a circuit for performing interpolation to connect a digital value of the level and position of the extracted point which is reproduced or transmitted with a digital value of the level and position of a point which is succeedingly extracted , in a substantially linear manner , in order to expand the video signal , and a circuit for mixing a composite synchronizing signal which is separately produced with the analog video signal , to obtain the original composite video signal .