Abstract: A motion compensated encoder where motion vectors are selected based on the prediction error generated in localized areas of the encoded image and based on an available bit budget. The motion vectors are created by dividing the image into blocks of two sizes and by considering the best mix of large and small size blocks, and their associated motion vectors, that minimize the overall prediction error, within the constraints of the bit budget. For convenience, the image division is arranged so that a given number of small sized blocks forms one large sized block (e.g. 16:1). Also, the block sizes are arranged so that employing only large sized blocks does not exceed the given bit budget, while employing only the small sized blocks does exceed the given bit budget.

Abstract: A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer.

Abstract: In a differential PCM encoder, the problem of error perpetuation is solved by leaking a changing, rather than a fixed, fraction of the input signal to the differential PCM. The fraction leaked is sensitive to the characteristics of the signal. In one embodiment the fraction leaked is fixed for a frame in accordance with a chosen characteristic of the frame signal. In another embodiment, the fraction leaked is set in accordance with one function when a chosen characteristic of the frame signal exceeds a given level, and follows another function when the chosen characteristic does not exceed the chosen level. In a still another embodiment, the fraction leaked is set to one of two levels, based on a chosen characteristic of the frame signal.

Abstract: An HDTV receiver design includes a reconstruction section and an inner loop section. The reconstruction section comprises a receiving section for accepting the television receiver's antenna signals, for separating out the component signals from the received signals and for decoding the separated signals. The decoded signals are applied to a quantization decoder that is responsive to vector codebook and to applied quantized vector signals, and the output signals of the quantization decoder are applied to an inverse DCT circuit. The inner loop comprises an adder for adding an estimate signal to the output of the DCT circuit, a frame buffer, a motion compensation circuit that is capable of translating large blocks as well as small blocks and a leak circuit that modulates the output of the motion compensator circuit in accordance with a received leak control signal.

Abstract: Graceful degradation for digitally encoded HDTV signals is achieved by appropriately coding the image to provide a controllable degradation of chosen image characteristics, such as temporal degradation, spatial degradation, and dynamic range degradation. In the temporal degradation approach of this invention, the resolution of movement suffers when noise is introduced. In the spatial degradation approach, the spatial resolution of the image is sacrificed. In the range degradation approach, the dynamic range of the signals is sacrificed. The graceful degradation is achieved by dividing the transmitted signal into two or more parts, such as parts A, B and C. Part A is given the heaviest error-correcting code; part B is given a "medium" error correcting code; and part C the is given the least powerful error correcting code (or perhaps none at all). A receiver that is close to the transmitter most likely receives parts A, B and C.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing much of the redundancies in the signal, efficiently encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. To enhance noise immunity a number of techniques are employed. One is to encode adjacent low-amplitude signals into larger signal samples, another one is the introduction of a controllable gain feature, a third one is the introduction of both fixed and variable leak, and still another one is the incorporation of signal scrambling.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal, encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. In the encoding, groups of signals to be sent are mapped to codebook vectors and the identities of the codebook vectors are sent together with those signals of the groups of signals that correspond to the codebook vectors. To insure that the total number of signals that are sent does not exceed the available capacity, the signals are sorted by a selected importance parameter and assigned for transmission in descending order of importance until the capacity is exhausted. Signals that are not assigned for transmission are discarded.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal and encoding the remaining signals. In the encoding, a portion of the signals to be transmitted is created in the form of an analog signal or a concatenated plurality of pulse amplitude coded samples (A-signal), and another portion of the signals to be transmitted is created in digital form (D-signal). The D-signal is consigned to a specified portion of the transmitted signal, leaving the remainder of the transmission capacity for the A-signal. When the normally created digital signals do not fully occupy the digital portion, enhanced operation results when selected ones of the analog signals or samples are excised from the A-signal, encoded digitally, and added to the D-signal. The excising of those signals leaves room in A-signal portion to include additional analog signals. This leads to an overall better image reproduction at the receiver.