Embedding watermarks into compressed video data

A method for adding a watermark to a compressed video bitstream comprising the steps of:

• receiving the compressed video bitstream together with site data specifying a plurality of sites within the compressed video bitstream which are apt for modification to embed a watermark into the compressed video bitstream;
• modifying a DCT coefficient for at least some of the plurality of sites specified by the received site data thereby embedding the watermark into the compressed video bitstream;
• and
• re-transmitting the watermarked compressed video bitstream containing the modified DCT coefficients.

A method for adding a watermark to a video signal comprising the steps of:

• receiving the compressed video bitstream together with site data specifying a plurality of sites within the compressed video bitstream which are apt for modification to embed a watermark into the compressed video bitstream;
• modifying a DCT coefficient for at least some of the plurality of sites thereby embedding the watermark into the compressed video bitstream;
• and
• decoding the watermarked compressed video bitstream containing the modified DCT coefficients to produce therefrom a video signal that is suitable for display on a television set, and that has the watermark embedded therein.

A method for adding a watermark to a video signal comprising the steps of:

• receiving the compressed video bitstream;
• selecting a plurality of sites within the compressed video bitstream that encode a DCT coefficient which is apt for modification to embed a watermark into the compressed video bitstream;
• modifying the DCT coefficient for at least some of the selected plurality of sites so the modified DCT coefficient occupies a number of bits in the compressed video bitstream that does not exceed a number of bits occupied by that same DCT coefficient before modification, thereby embedding the watermark into the compressed video bitstream;
• and
• decoding the compressed video bitstream containing the modified DCT coefficients to produce therefrom a video signal that is suitable for display on a television set, and that has the watermark embedded therein.

A system for detecting an unauthorized copy of a video by identifying a watermark that has been embedded into a compressed video bitstream produced from an un-watermarked video by changing values of selected DCT coefficients at watermarking sites in the compressed video bitstream, the system comprising:

• an original video input for receiving a video signal of the un-watermarked video;
• a copy video input for receiving a video signal of the copy of the video which may possibly include the watermark;
• a frame differencer that receives from said original video input and from said copy video input the video signals received thereat, said frame differencer producing a synchronized, frame-by-frame difference between the video signal received by said original video input and the video signal received by said copy video input;
• and
• watermark identification means that receives the frame-by-frame difference produced by said frame differencer and also receives a site list containing data which specifies characteristics of sites at which the watermark may be embedded into the video signal received by said copy video input, said watermark identification means permitting detection of the watermark embedded into the video signal received by said copy video input.