Abstract: An arithmetic logic unit is disclosed herein which overcomes problems in the art discussed above. In accordance with the present invention, an ALU includes a plurality of individual programmable logic units which selectively implement arithmetic, logic, and equality comparison operations. One bit of each of two or more input signals is provided to respective ones of the logic units. One of a plurality of function signals, each of which being set equal to the truth table for a particular arithmetic, logic, or equality operation, is selectably provided to each of the logic units. Each of the logic units multiplexes the function signal provided thereto according to the particular bits of the input signals received therein to generate first and second output signals. These first and second output signals provided by each of the logic units are combined in an adder such that the resulting bit pattern represents the selected arithmetic, logic, or equality operation of the two or more input signals.

Abstract: A motion compensation structure and a method are provided for decoding interframe coded video data using motion vectors. The motion compensation structure includes a filter for resampling the pixel data in both vertical and horizontal directions, a prediction memory structure and a weighted adder structure. In one embodiment of the present invention, a weighted adder structure and a method are provided for performing bilinear interpolation of two values using multiplexers and an multiple-input adder.

Abstract: A signed multiplier circuit which performs selectable multiplication operations on a first word having an upper byte and a lower byte and a second word having an upper byte and a lower byte. A first multiplier means generates a first product representative of the product of the upper bytes of the first and second words and the product of the lower bytes of the first and second words. A second multiplier means generates a second product representative of the product of the upper byte of the first word and the lower byte of the second word plus the product of the lower byte of the first word and the upper byte of the second word. The second multiplier means can be selectively disabled. When the second multiplier means is enabled, the multiplier circuit multiplies the first and second words. When the second multiplier means is disabled, the multiplier circuit multiplies the upper bytes of the first and second words and the lower bytes of the first and second words.

Abstract: A structure and a format for providing a video signal encoder under the MPEG standard are provided. In one embodiment, the video signal interface is provided with a decimator for providing input filtering for the incoming signals. In one embodiment, the central processing unit (CPU) and multiple coprocessors implements DCT and IDCT and other signal processing functions, generating variable length codes, and provides motion estimation and memory management. The instruction set of the central processing unit provides numerous features in support for such features as alpha filtering, eliminating redundancies in video signals derived from motion pictures and scene analysis. In one embodiment, a matcher evaluates 16 absolute differences to evaluate a "patch" of eight motion vectors at a time.

Abstract: In accordance with the present invention, an adder is disclosed which combines byte boundary control signals with propagate-generate signal pairs immediately resulting from bit pairs of the input signals. Combining the byte boundary control signals with the first level propagate-generate signal pairs, rather than combining the byte boundary control signals with propagate-generate signal pairs indicative of the carry-out of a byte, allows the adder to utilize a more efficient tree signal path topology in which multiple levels of circuitry may be eliminated, thereby resulting in a reduction in propagation delay.

Abstract: A method of approximating the pixel intensity values of a current block using the pixel intensity values of a search window, wherein the precision of the number of bits used to represent the pixel intensity values is reduced. The pixel intensity values of the pixels in the current block are averaged to determine a first average pixel intensity value. The pixel intensity values of the current block which have a pixel intensity value less than the first average pixel intensity value are averaged to determine a second average pixel intensity value. The pixel intensity values of the current block which have a pixel intensity value greater than the first average pixel intensity value are averaged to determine a third average pixel intensity value. The first, second and third average pixel intensity values are used to determine thresholded pixel intensity values for the current block pixels and the search window pixels, thereby creating a thresholded current block and a thresholded search window.

Abstract: A single dirty bit is maintained in a memory controller for each cache line of a cached memory system using a cache write-back policy. The dirty bit is set after each write access, is reset after each read access in which a cache miss occurs, and is left unchanged after all other memory accesses. The dirty bit is used to select a delay value for submitting a retry request packet after a cache miss occurred in a memory access. The delay value minimizes memory access time by allowing for a write-back operation only when necessary.

Abstract: A structure and a format for providing a video signal encoder under the MPEG standard are provided. In one embodiment, the video signal interface is provided with a decimator for providing input filtering for the incoming signals. In one embodiment, the central processing unit (CPU) and multiple coprocessors implements DCT and IDCT and other signal processing functions, generating variable length codes, and provides motion estimation and memory management. The instruction set of the central processing unit provides numerous features in support for such features as alpha filtering, eliminating redundancies in video signals derived from motion pictures and scene analysis. In one embodiment, a matcher evaluates 16 absolute differences to evaluate a "patch" of eight motion vectors at a time.

Abstract: A structure and method for using variable length instructions in an instruction register having a fixed word boundary. The instruction register accommodates a first word and a second word. The first word has a first base instruction and a first flexible instruction aligned with first and second predetermined positions, respectively, in the instruction register. The second word has a second base instruction and a second flexible instruction aligned with third and fourth predetermined positions, respectively, in the instruction register. The first and second base instructions and the first and second flexible instructions each have a fixed length. The first base instruction can (1) stand alone as an independent instruction, (2) be combined with the first flexible instruction to form a once-extended instruction, or (3) be combined with the first and second flexible instructions to form a twice-extended instruction.

Abstract: A multiplier circuit for use in a system which includes an arithmetic and logic unit (ALU). The multiplier circuit includes a carry save stage which receives a first data value and a second data value, and in response, creates a carry signal and a sum signal. The carry and sum signals are provided to input leads of the ALU. The ALU is used to add the carry and sum signals to create a third data value which is equal to the product of the first and second data values. In one embodiment, the input leads to the ALU are multiplexed. Thus, one input lead of the ALU receives either the carry signal or a signal from a first input node and the second input lead of the ALU receives either the sum signal or a signal from a second input node.

Abstract: A structure and a format for providing a video signal encoder under the MPEG standard are provided. In one embodiment, the video signal interface is provided with a decimator for providing input filtering for the incoming signals. In one embodiment, the central processing unit (CPU) and multiple coprocessors implements DCT and IDCT and other signal processing functions, generating variable length codes, and provides motion estimation and memory management. The instruction set of the central processing unit provides numerous features in support for such features as alpha filtering, eliminating redundancies in video signals derived from motion pictures and scene analysis. In one embodiment, a matcher evaluates 16 absolute differences to evaluate a "patch" of eight motion vectors at a time.

Abstract: A 2-dimensional display space is mapped into the external DRAM addresses by embedding in the address space X and Y vectors of the display space. The mapping of the X and Y vectors allows a macroblock of pixels to be stored in one DRAM memory page, so that an access to a macroblock can be efficiently accomplished under a page mode access to the DRAM page. By providing control to one address bit, data of four pixels can be obtained at one time in one of 2 pixel.times.2 pixel "quad pixel" configuration, or in a 4 pixel.times.1 pixel horizontal "scan" configuration. In addition, a structure and a method are provided for accessing a 16.times.16-pixel picture area in two parts, in order that the number of DRAM page boundaries crossed during access of the 16.times.16-pixel picture area is minimized, thereby increasing the efficiency of memory access by reducing the overhead cost of initial accesses under page mode access to DRAMs.

Abstract: A method and a structure are provided to decode intra-frame and interframe coded compressed video data. In one embodiment of the present invention, a decompression structure having a processor is provided with a global bus over which a decoder coprocessor, an inverse discrete cosine transform coprocessor and a motion compensation coprocessor communicate. The decompression structure in accordance with the present invention communicates with a host computer over a host bus and with an external dynamic random access memory over a memory bus. The processor in the decompression structure of the present invention provides overall control to the decoder, IDCT and motion compensation coprocessors by reading and writing into a plurality of data and control registers, each register associated with one of the decoder, the IDCT and the motion compensation coprocessors.

Abstract: A structure and a format provide a video signal encoder under the MPEG (Motion Picture Experts Group) standard. In one embodiment, the video signal interface is provided with a decimator for providing input filtering for the incoming signals. In one embodiment, the central processing unit (CPU) and multiple coprocessors implements discrete cosine transform (DCT) and inverse discrete cosine transform (IDCT) and other signal processing functions, generating variable length codes, and provides motion estimation and memory management. The instruction set of the central processing unit provides numerous features in support for such features as alpha filtering, eliminating redundancies in video signals derived from motion pictures and scene analysis. In one embodiment, a matcher evaluates 16 absolute differences to evaluate a "patch" of eight motion vectors at a time.

Abstract: A multiplier circuit which performs selectable multiplication operations on a first word having an upper byte and a lower byte and a second word having an upper byte and a lower byte. A first multiplier circuit generates a first product representative of the product of the upper bytes of the first and second words and the product of the lower bytes of the first and second words. A second multiplier circuit generates a second product representative of the product of the upper byte of the first word and the lower byte of the second word plus the product of the lower byte of the first word and the upper byte of the second word. The second multiplier circuit can be selectively disabled. When the second multiplier circuit is enabled, the multiplier circuit multiplies the first and second words. When the second multiplier circuit is disabled, the multiplier circuit multiplies the upper bytes of the first and second words and the lower bytes of the first and second words.

Abstract: A separate data stream allows encoding of an overlay image, which is to be superimposed on images of a video sequence. The pixels of the overlay image can be transparent or have a text color, a shadow color, or an intermediate color either between the text color and the shadow color, or between the shadow color and the color of the corresponding pixel in the underlying video image. The intermediate colors provide for antialiasing. In addition, a color selection circuit allows selection of the next color from a pool of 9 colors, using a 3-bit field.

Abstract: A shifter circuit and method for simultaneously and independently shifting and reordering a plurality of data bytes. The shifter circuit includes first and second registers which each receive a plurality of data bytes. The first register is coupled to a plurality of first buses, with each of the first buses receiving a data byte from the first register. Similarly, the second register is coupled to a plurality of second buses, with each of the second buses receiving a data byte from the second register. A multiplicity of third buses are coupled to the first and second buses. A byte shifting multiplexer is coupled to each of the third buses. A plurality of bit shifting multiplexer are coupled to the byte shifting multiplexers, with each bit shifting multiplexer being coupled to a pair of byte shifting multiplexers. A control circuit is coupled to the byte shifting and bit shifting multiplexers. The control circuit provides for independent control of each of the byte shifting multiplexers.

Abstract: A method and a structure are provided to decode intraframe and interframe coded compressed video data. In one embodiment, a decompression structure having a processor is provided with a global bus over which a decoder coprocessor, an inverse discrete cosine transform coprocessor and a motion compensation coprocessor communicate. The decompression structure communicates with a host computer over a host bus and with an external dynamic random access memory over a memory bus. The processor provides overall control to the coprocessors by reading and writing into a plurality of data and control registers, each register associated with one of the coprocessors. A structure including four of the decompression structures and a method are provided for decoding high definition television (HDTV) signals. In this structure for decoding HDTV signals, each decompression structure decodes a 480.times.1088-pixel picture area with access to up to two additional 240.times.1088-pixel picture areas.

Abstract: A digital video compression system and an apparatus implementing this system are disclosed. Specifically, matrices of pixels in RGB, YUV or CMYK formats are accepted for data compression. The data are rearranged in 8x8 pixel blocks, each block being of one pixel component type. The pixel data are then subjected to a discrete cosine transform (DCT). A quantization step eliminates DCT coefficients having amplitude below a set of preset thresholds. The video signal is further compressed by coding the elements of the quantized matrices in a zig-zag manner. This representation is further compressed by Huffman codes. Decompression of the signal is substantially the reverse of compression steps. The inverse discrete cosine transform (IDCT) may be implemented by the DCT circuit. The circuits may be implemented in a single integrated circuit chip. Three levels of compression rate control are provided during processing of video data.