Abstract: Improved compression of digital signals relating to high resolution video images is accomplished by an adaptive and selective coding of digital signals relating to frames and fields of the video images. Digital video input signals are analyzed and a coding type signal is produced in response to this analysis. This coding type signal may be used to adaptively control the operation of one or more types of circuitry which are used to compress digital video signals so that less bits, and slower bit rates, may be used to transmit high resolution video images without undue loss of quality. For example, the coding type signal may be used to improve motion compensated estimation techniques, quantization of transform coefficients, scanning of video data, and variable word length encoding of the data. The improved compression of digital video signals is useful for video conferencing applications and high definition television, among other things.

Abstract: A quantization parameter for use in encoding a region of an image is developed from a) a categorization of the region into one of a predetermined plurality of perceptual noise sensitivity (PNS) classes, b) a level of psycho-visual quality that can be achieved for the encoded version of the image, the level being selected from among a plurality of predetermined levels, and c) a prestored empirically derived model of the relationship between the PNS classes, the psycho-visual quality levels and the values of the quantization parameter. PNS indicates the amount of noise that would be tolerable to a viewer of the region, i.e., the perceptual sensitivity of the region to noise. Some characteristics on which PNS classes may be based are: spatial activity, speed of motion, brightness of the region, importance of the region in a particular context, the presence of edges within the region and the texture of the region, e.g., from "flat" to "highly textured".

Abstract: Individual frames in a video signal are encoded using different coding techniques such as intraframe, motion compensated prediction and motion compensated interpolation coding. The encoder output, which is produced at a first highly variable rate, is applied to a channel via a buffer that outputs the encoded signal at a second, less variable rate. The rate allocated to different frame types is determined as a function of the type of frame being encoded and the coding technique being used. A second buffer may be used to eliminate almost all variations in the rate at which data is applied to the channel. Buffer fullness may control characteristics of the encoder such as quantizer step size and/or prefiltering.