METHOD AND DEVICE OF CODING A DIGITAL VIDEO SIGNAL FOR REPRODUCTION OF PICTURES WITH A HIGH QUALITY EVEN UPON OCCURRENCE OF A DRASTICAL CHANGE BETWEEN THE PICTURES

摘要

Abstract of the DisclosureOn subjecting a digital video signalrepresentative of successive pictures to predictivecoding by using correlation between two successivepictures, an estimated result is derived from thedigital video signal to represent a degree ofcorrelation between a current picture and a previouspicture and is increased with a reduction of the degree.When the estimated result becomes greater than apredetermined threshold value as a result of a drasticalchange, such as a scene change, from the previouspicture to the current picture, a control signal isproduced. Furthermore, the digital video signal isseparated into a preceding signal part ending at theprevious picture and a succeeding part which begins atthe current picture. The control signal controls thepredictive coding so that the succeeding part be codedwith an area of predictive coding of each picturegradually widened with time. The control signal may besupplied to a predictive coder. Alternatively, thecontrol signal may be used to control a frame memory forsupplying the digital video signal to the predictivecoder with the area gradually widened for the succeedingpart. A plurality of threshold levels may be usedcollectively as the predetermined threshold. Thethreshold levels are for use in selecting a rate ofgradually widening the area.