Abstract: A circuit arrangement for controlling audio signal transmissions for a communications system that includes a microphone and a video camera. The arrangement comprises a video processor configured and arranged to receive a video signal from the video camera, detect movement of an object in the video signal, and provide a motion-indicating signal indicating movement relative to the object. An audio processor is coupled to the video processor and is configured and arranged to modify the audio signal to be transmitted responsive to the motion-indicating signal. In another embodiment, a video signal processor is configured and arranged to receive a video signal from the video camera, detect mouth movement of a person and provide a mouth-movement signal indicative of movement of the person's mouth.

Abstract: A method for generating a digital motion video sequence at a plurality of bit rates uses a transitional coding source when switching between bitstreams having different bit rates during transmission of a video sequence. The transitional data may be frames coded using reconstructed frames reconstructed for a first bitstream using the characteristics of the second bitstream. These “low bit rate insert frames,” or LBIFs, contain the image characteristics of a signal coded at the lower bit rate. With a bitstream having a higher bit rate being periodically coded using an LBIF, a point of image continuity between the two bitstreams is provided. Thus, switching from one bitstream to the other at this point in the video sequence minimizes the production of artifacts caused by differences in bit rate. In another embodiment of the invention, a separate set of transitional data is created, taking the form of “switch” frames, or S-frames.

Abstract: Coding and decoding of video images includes the use of multiple reference pictures and determining motion vector and time delay information for the video images. Video images are quantized and transmitted with the motion vector and time delay information from a first station to a second station. A new video image is predicted for display at the second station as function of the motion parameter codes and multiple reference pictures. The invention may be used in connection with a video communication and/or video conferencing system as a long-term memory predictor to improve image-coding efficiencies and motion compensation. The long-term memory prediction extends the spatial displacement utilized in block-based hybrid video coding by a variable time delay. The arrangement and method employ a proposed bit allocation scheme to provide increased coding efficiencies of the video coder.

Abstract: A variable length coding system encodes and decodes symbols as uniquely decodable code words using an assignment scheme having a maximum code word length. According to one embodiment, a first bitstream is combined with a second bitstream to provide a resultant bitstream to be sent over a communications channel. The first bitstream represents the code words in a forward direction, and the second bitstream contains the same code words reversed and bit delayed by at least the maximum code word length. A resultant bitstream can be decoded in forward or reverse direction. The scheme is highly efficient for long blocks of data and the reversible aspect of the coding scheme improves the tolerance for errors caused by channel interference.

Abstract: Coding and decoding of video images includes the use of multiple reference pictures and determining motion vector and time delay information for the video images. Video images are quantized and transmitted with the motion vector and time delay information from a first station to a second station. A new video image is predicted for display at the second station as function of the motion parameter codes and multiple reference pictures. The invention may be used in connection with a video communication and/or video conferencing system as a long-term memory predictor to improve image-coding efficiencies and motion compensation. The long-term memory prediction extends the spacial displacement utilized in block-based hybrid video coding by a variable time delay. The arrangement and method employ a proposed bit allocation scheme to provide increased coding efficiencies of the video coder.

Abstract: A method is provided for performing a fast Discrete Cosine Transform (DCT) and a fast Inverse Discrete Cosine Transform (IDCT) in a software implementation. The method provided exploits symmetries found in both the DCT and IDCT. As a result of the symmetries found in the DCT and IDCT, both transforms may be performed using a combination of look-up tables and butterfly operations, thus employing only a small number of additions and subtractions and no multiplications. Furthermore, there is provided an aspect of the present invention which exploits the excess precision available in current central processing units (CPUs) relative to the precision required by the DCT and IDCT calculations.

Abstract: An image processing system operates at reduced resolution to reduce computational complexity while remaining fully compatible with full resolution decoders. A video input signal is subsampled and encoded at the resulting lower resolution. The encoded signal is filled with zero terms to produce an encoded signal having the same number of terms as a full resolution encoded signal. In a motion-compensated hybrid coder, the decoder section also includes a subsampling system, so that the reconstructed video signal is produced at the same resulting lower resolution. The encoder section and the decoder section are each inverse functions of the other, eliminating a drift problem associated with prior systems.

Abstract: An image processing system operates at reduced resolution to reduce computational complexity while remaining fully compatible with full resolution decoders. A video input signal is subsampled and encoded at the resulting lower resolution. The encoded signal is filled with zero terms to produce an encoded signal having the same number of terms as a full resolution encoded signal. In a motion-compensated hybrid coder, the decoder section also includes a subsampling system, so that the reconstructed video signal is produced at the same resulting lower resolution. The encoder section and the decoder section are each inverse functions of the other, eliminating a drift problem associated with prior systems.

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 system for, and method of, enhancing a digitized image signal according to a helper signal architecture are described. The architecture includes an analysis filter, responsive to a digitized image signal, for filtering the digitized image signal, corresponding to a first frequency band, to produce a first frequency band signal. The first frequency band signal is then applied to a point operator, which modifies the first frequency band signal in accordance with a non-linear characteristic. The non-linear characteristic includes a first region having a negative slope for low amplitude input signals. The non-linearity further includes a second region having a positive slope for informational components of an input signal so that informational components of the first frequency band signal cause the point operator to produce a modified signal having components that relate to the input signal according to the positive slope.

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 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.

Abstract: A method and apparatus for transmitting a sequence of image frames by encoding interframe error data features the steps of compiling a spatially decomposed image of a background of the sequence of image frames, spatially decomposing a warped image of a previous frame, and spatially decomposing a new input image. The spatially decomposed input image is compared with the spatially decomposed background image and with the spatially decomposed warped image. An error signal defining the spatially decomposed input image is generated based on these comparisons.

Abstract: A method and apparatus for encoding interframe error data in an image transmission system, and in particular in a motion compensated image transmission system for transmitting a sequence of image frames from a transmitter to a receiver, employ hierarchical entropy coded lattice threshold quantization to increase the data compression of the images being transmitted. The method and apparatus decimate an interframe predicted image data and an uncoded current image data, and apply hierarchical entropy coded lattice threshold quantization encoding to the resulting pyramid data structures. Lossy coding is applied on a level-by-level basis for generating the encoded data representation of the image difference between the predicted image data and the uncoded original image. The method and apparatus are applicable to systems transmitting a sequence of image frames (or other pattern data, such as speech) both with and without motion compensation.

Abstract: A range camera is provided for the determination of range to an object through the utilization of a system which projects a limited depth of field light pattern onto an object and measures the blurring of the pattern on the object. In one embodiment an anisotropic aperture or astigmatic optics are used in combination with an isotropic pattern to eliminate system error introduced by the camera. The anisotropic aperture provides that blurring takes place only in a given direction, with measurement of blurring in an orthogonal direction providing an output only responsive to the blurring associated with the camera. This blurring can then be subtracted out to eliminate system error from the range measurement. The range camera is operative to produce a range picture or map, with optional outputs providing localized albedo and a conventional brightness image.

Abstract: A range camera is provided for the determination of range to an object through the utilization of a system which projects a limited depth of field light pattern onto an object and measures the blurring of the pattern on the object. In one embodiment an anisotropic aperture or astigmatic optics are used in combination with an isotropic pattern to eliminate system error introduced by the camera. The anisotropic aperture provides that blurring takes place only in a given direction, with measurement of blurring in an orthogonal direction providing an output only responsive to the blurring associated with the camera. This blurring can then be subtracted out to eliminate system error from the range measurement. The range camera is operative to produce a range picture or map, with optional outputs providing localized albedo and a conventional brightness image.