US 5,809,139 A · Watermarking method and apparatus for compressed digital video

Abstract

A digital watermarking method and apparatus allows for the watermarking of a digital video signal in a compressed form, thereby allowing watermarking of a pre-compressed video sequence without requiring the decoding and re-coding of the signal. The watermark signal is a sequence of information bits which has been modulated by a pseudo-random noise sequence to spread it in the frequency domain. The video signal is transform coded, preferably with a discrete cosine transform, and a watermark signal, which has been transform coded using the same type of transform, is added to the coded video signal. The system also includes bitstream control to prevent an increase in the bit rate of the video signal. This allows the system to be used with transmission channels having strict bit rate constraints. For each transform coefficient of the video signal, the number of bits necessary to encode the watermarked coefficient is compared to the number of bits necessary to encode the unwatermarked coefficient. If more bits are required to transmit a watermarked coefficient than to transmit the corresponding unwatermarked coefficient, the watermarked coefficient is not output, and the unwatermarked coefficient is output in its place. When watermarking interframe coded data, a drift compensation signal may be used to compensate for the accumulating variations in the decoded video signal stored at the receiver. The system may also include an encryption/decryption capability, with the watermarking apparatus located at either the transmitting or receiving end of the transmission channel.

Claims36

Dependent claims

A method of embedding a watermark in a first portion of a digital video signal bitstream containing a digital video signal that has been processed using a hybrid interframe coder to transform the digital video signal into a plurality of video transform coefficients and code the video transform coefficients to a compressed video format, wherein the watermark comprises a predetermined sequence of information bits transformed into a plurality of watermark transform coefficients, the method comprising:

decoding the compressed video format to recover the plurality of video transform coefficients;
summing the watermark transform coefficients with the video transform coefficients to generate watermarked video coefficients;
and
preventing drift in the first portion of the bitstream by compensating for artifacts resulting from previously added watermark transform coefficients.

1 more element

decoding the compressed video format to recover the plurality of video transform coefficients;
summing the watermark transform coefficients with non-zero video transform coefficients to generate watermarked video coefficients;
preventing drift in the first portion of the bitstream by determining a difference signal indicative of the difference between a portion of the video transform coefficients before summing with the watermark transform coefficients and a corresponding portion of the watermarked video signal after summing with the watermark transform coefficients, and applying the difference signal to subsequent portions of the watermarked video signal;
and
coding the watermarked video coefficients to a compressed watermarked video format.

2 more elements

Apparatus for embedding a watermark in a first portion of a digital video signal bitstream containing a digital video signal that has been processed using a hybrid interframe coder to transfer the digital video signal into a plurality of video transform coefficients and code the video transform coefficients to a compressed video format, wherein the watermark comprises a predetermined sequence of information bits transformed into a plurality of watermark transform coefficients, the apparatus comprising:

a decoder for decoding the compressed video format so as to recover the plurality of video transform coefficients;
summing apparatus for summing the watermark transform coefficients with the video transform coefficients to generate watermarked video coefficients;
and
a drift compensator to prevent drift in the first portion of the bitstream by compensating for artifacts resulting from previously added watermark transform coefficients.

1 more element

A computer program product for embedding a watermark in a first portion of a digital video signal bitstream containing a digital video signal that has been processed using a hybrid interframe coder to transform the digital video signal into a plurality of video transform coefficients and code the video transform coefficients to a compressed video format, wherein the watermark comprises a predetermined sequence of information bits transformed into a plurality of watermark transform coefficients, the program code comprising;

program code for decoding the compressed video format to recover the plurality of video transform coefficients;
program code for summing the watermark transform coefficients with the video transform coefficients to generate watermarked video coefficients;
and
program code for preventing drift in the first portion of the bitstream by compensating for artifacts resulting from previously added watermark transform coefficients.

1 more element

Dependencies are inferred from the claim text.

Watermarking method and apparatus for compressed digital video

Life of this patent

Watermarking method and apparatus for compressed digital video

Life of this patent

Abstract

Claims36