In order to avoid the presence of undesired semi-transparent region around the caption, a different approach from the usual pixel domain compositing operation is adopted.

• 由于叠加字幕中字形状的非规则性,在压缩域中叠加会出现不希望看到的方框阴影区域,该文采用在压缩域中矩阵的卷积运算来解决这个问题。