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.

Abstract: A method is provided for performing a fast 3-coefficient Discrete Cosine Transform (DCT) in a software implementation. The method provided exploits symmetries and statistical properties of the coefficients found in the DCT. As a result of the symmetries and statistical distribution of coefficients typically found in the DCT of typical images in image processing applications, the 3-coefficient DCT may be readily performed using as few as three input sample values from an input image block. The method selects the samples from locations in the image block where they are at peaks of the basis functions for the coefficients included, thus maximizing noise immunity. The method also provides for switching between performing the 3-coefficient DCT and a full (or other) DCT as required by image quality. Finally, the method may be generalized to perform a reduced coefficient DCT of any number of coefficients less than all coefficients in a complete output block.

Abstract: A method of processing a digital signal wherein multiple signal values are simultaneously operated upon in a single register. The register is not segmented in hardware, but is segmented by operation of a controlling computer software program. The controlling computer software arranges the digital signal in a computer memory in such a manner as to permit the register to be loaded with a plurality of digital samples, each having a precision less than the total precision available in the register. The method may include steps to partially compensate for errors introduced by carries from one segment of the register to another segment of the register, when necessary.

Abstract: A computer teleconferencing method and apparatus are provided which permits transmission of video image sources including both computer display images and other video images. The apparatus may include at a local teleconferencing site a personal computer having a video graphics adapter, a monitor and a digital telephone interface. The digital telephone interface is used to establish communications with a remote teleconferencing site. The apparatus may further include a video camera and a video capture system connected into the personal computer. The method may include steps of capturing snapshots of a computer display image, converting those snapshots to a digital television form, and compressing and transmitting the digital television signal to the remote teleconferencing site.

Abstract: A system and method for generating gamma-predistorted video signals. A close approximation to the ideal gamma predistorted values of Y, Cr and Cb video signal components are generated from linear camera or computer output signals using at most a single matrix multiplication, one channel of inverse gamma function generation (on the luminance component) and two table look up operations. The linear luminance value is predistorted by an inverse gamma function. If they are not available from the video source, a matrix multiplication is used to generate linear luminance and chrominance signals. The linear chrominance signals are then adjusted for their dependence on luminance using a two-dimensional table look-up. The lookup table(s) is (are) addressed by the linear luminance value and by each of the linear chrominance values to produce gamma-predistorted Cr and Cb signals from the tables.