Multiplexing / demultiplexing method for superimposing subpictures on a main picture

摘要

The main picture and at least one subpicture for superimposing the main picture are encoded in the following manner. The main image includes positional information indicating positional information of each main image region in the main image, and is divided into a plurality of main image regions that are compressed and encoded. The sub-picture includes positional information indicating a position where each sub-picture region overlaps the main image region, and is divided into a plurality of sub-picture regions that are compressed and encoded. Thereafter, the encoded data of the main image and the sub-picture region are arranged in such a manner that the main image region and the sub-picture region sharing the same positional information so that the encoded data of the sub-picture region precedes the one of the main image region. . The encoded video sequence thus obtained is decoded in the following manner. The current area is decoded to obtain coded data. Next, if the positional information of the current area is the same as that of the previous area, one of the following steps (1) or (2) is performed: (1) When the sub-picture is displayed, the decoded data of the current area is discarded: (2) If the sub-picture area is not displayed, the decoded data of the previous area is replaced with that of the current area.