| 摘要 |
A method and apparatus for modifying a compression encoded video sequence representing a video image are described. The compression encoded video sequence includes a group of pictures comprising an intra-encoded picture and at least one inter-encoded picture, the inter-encoded picture comprising a plurality of image blocks. At least one of the image blocks has a motion vector representing a displacement of the image block with respect to a reference image block in another picture in the group of pictures, and a difference signal representing a difference between the image block and the reference image block. The method comprises the steps of detecting, for each group of pictures, the inter-encoded pictures within the video sequence, extracting the image blocks from the detected inter-encoded pictures, compressing at least a portion of the extracted image blocks to form compressed image block data, and inserting replacement image blocks and the compressed image block data into the video sequence to replace the extracted image blocks. The replacement image blocks each have a motion vector of value zero and a difference signal of value zero. By providing replacement picture data which represents replacement image blocks having a motion vector of value zero and a difference signal of value zero, sets the inter-encoded pictures of the modified video sequence to display, when decoded, the same image as that displayed on the previous intra-encoded picture, thereby providing a form of removable (washable) impairment such as a visible watermark. |
