VIDEO ENCODER AND DECODER USING REGION BASED CODING AND DECODING TECHNIQUES WITH SEQUENTIAL REFRESH

A video encoder that encodes each of a plurality of blocks obtained by dividing an input image, includes: a definition unit configured to define a valid area which is allowed to be used as reference in a reference image in interframe coding; a detection unit configured to detect a reference area in the reference image for a target block; a predicted image generation unit configured to generate a predicted image by outputting an image of the reference area for the reference area belonging to the valid area and outputting a complementary image for the reference area not belonging to the valid area; and a coding unit configured to encode the input image using the predicted image, wherein valid area information indicating the valid area is transmitted to a video decoder, for each group of a plurality of blocks.