Abstract: A variable length decoder (VLD) for decoding MPEG-1 and -2 syntax compliant video bit streams. The VLD includes a micro-sequencer and VLD command decode/execution unit for controlling the MPEG decoding process using a novel instruction set. The instruction set includes a set of commands for decoding the video data and a set of flow control instructions. A rotator/barrel shifter is provided for making a predetermined number of encoded bits from the video bit stream available to the VLD and a variable length table decoder for variable length decoding using the MPEG standard variable length code (VLC) tables. The variable length table decoder shares a prefix pattern matching scheme across all of the VLC tables and organizes the variable length codes into a series of subtables. Each subtable corresponds to one of the unique prefix patterns. Variable length codes are decoded by identifying a leading pattern in the video data bit stream and, in parallel, accessing the subtable corresponding to that leading pattern.

Abstract: A variable length decoder (VLD) for decoding MPEG-1 and -2 syntax compliant video bit streams. The VLD includes a micro-sequencer and VLD command decode/execution unit for controlling the MPEG decoding process using a novel instruction set. The instruction set includes a set of commands for decoding the video data and a set of flow control instructions. A rotator/barrel shifter is provided for making a predetermined number of encoded bits from the video bit stream available to the VLD and a variable length table decoder for variable length decoding using the MPEG standard variable length code (VLC) tables. The variable length table decoder shares a prefix pattern matching scheme across all of the VLC tables and organizes the variable length codes into a series of subtables. Each subtable corresponds to one of the unique prefix patterns. Variable length codes are decoded by identifying a leading pattern in the video data bit stream and, in parallel, accessing the subtable corresponding to that leading pattern.

Abstract: A variable length decoder (VLD) for decoding MPEG-1 and -2 syntax compliant video bit streams. The VLD includes a micro-sequencer and VLD command decode/execution unit for controlling the MPEG decoding process using a novel instruction set. The instruction set includes a set of commands for decoding the video data and a set of flow control instructions. A rotator/barrel shifter is provided for making a predetermined number of encoded bits from the video bit stream available to the VLD and a variable length table decoder for variable length decoding using the MPEG standard variable length code (VLC) tables. The variable length table decoder shares a prefix pattern matching scheme across all of the VLC tables and organizes the variable length codes into a series of subtables. Each subtable corresponds to one of the unique prefix patterns. Variable length codes are decoded by identifying a leading pattern in the video data bit stream and, in parallel, accessing the subtable corresponding to that leading pattern.

Abstract: A method and apparatus for concealing errors during decoding of a video bit stream utilize estimates, if possible, motion vectors in the temporal domain. If estimation in the temporal domain is not possible, motion vectors are estimated in the spatial domain. A macroblock is then estimated based upon the estimated motion vector. If estimation in the spatial domain is not possible, macroblock estimation is made without the use of an estimated motion vector.

Abstract: A method and apparatus for changing the number of scan lines in a frame of video data to produce an image represented by the video data that corresponds to a desired aspect ratio. The apparatus includes a pair of finite impulse response filters for processing the decoded chrominance and luminance pixel values stored in memory. The filters permit a plurality of scan lines of chrominance and luminance data to be read and filtered on a continuous basis with any scan line of data being read only once. Thus, the filters provide a very efficient method of providing a frame of a number of output scan lines of chrominance and luminance pixel values that are different from the number of scan lines of chrominance and luminance pixel values in a frame of video data stored in memory.

Abstract: A digital video presentation system is provided with hardware and software logic for mapping the picture data into buffer memory in a way that permits both the reading of motion vector compensated macroblocks of data and the reading of horizontal picture wide scan lines with a low number of memory page crossings. Preferably, the memory is a plurality of rows, for example 16 rows, wide. Preferably, 16 lines of 8-pixel (two 32 pixel wide column) line segments of 8×8 pixel blocks are stored in consecutive storage locations followed by the consecutive storage vertically adjacent line segments until one line segment is stored in each logical row of the memory. Then the next horizontally adjacent set of line segments of similarly stored until the right boundary of the picture is reached, then the each additional row of 16 lines of the picture similarly are stored until the bottom of the picture is reached.

Abstract: A method and apparatus for concealing errors during decoding of a video bit stream utilize estimates, if possible, motion vectors in the temporal domain. If estimation in the temporal domain is not possible, motion vectors are estimated in the spatial domain. A macroblock is then estimated based upon the estimated motion vector. If estimation in the spatial domain is not possible, macroblock estimation is made without the use of an estimated motion vector.

Abstract: A digital video presentation system is provided with hardware and software logic for mapping the picture data into buffer memory in a way that permits both the reading of motion vector compensated macroblocks of data and the reading of horizontal picture wide scan lines with a low number of memory page crossings. Preferably, the memory is a plurality of rows, for example 16 rows, wide. Preferably, 16 lines of 8-pixel (two 32 pixel wide column) line segments of 8.times.8 pixel blocks are stored in consecutive storage locations followed by the consecutive storage vertically adjacent line segments until one line segment is stored in each logical row of the memory. Then the next horizontally adjacent set of line segments of similarly stored until the right boundary of the picture is reached, then the each additional row of 16 lines of the picture similarly are stored until the bottom of the picture is reached. Each 16.times.

Abstract: A method and apparatus for concealing errors during decoding of a video bit stream utilize estimates, if possible, motion vectors in the temporal domain. If estimation in the temporal domain is not possible, motion vectors are estimated in the spatial domain. A macroblock is then estimated based upon the estimated motion vector. If estimation in the spatial domain is not possible, macroblock estimation is made without the use of an estimated motion vector.

Abstract: A special purpose reduced instruction set central processing unit (RISC CPU) for controlling digital audio/video decoding. The instruction set includes flow control instructions which incorporate immediate values, used to jump over a small number of instructions, and other instructions used for larger jumps. Also, instructions obtain data from the video decoder of the ASIC in a streamlined fashion, using video decoder addresses hard-coded into the RISC CPU. Further instructions perform manipulations of individual bits of registers used as state/status flags. The RISC CPU includes watchdog functions for monitoring the delivery of data to the RISC CPU from other functional units or from memory, so that the RISC CPU can execute instructions while delivery of data from memory or other functional units is pending, unless that data is necessary for program execution, in which case, program execution stalls until the data arrives.

Abstract: An improved architecture for a digital video processor that processes subvideo data to be superimposed on a main video image during a display image scanning process. The improved digital video processor divides and partitions the execution of subvideo data between a programable CPU and a dedicated hardware processor. The CPU is used to process the simpler, less time critical, nonpixel data, and the more complex, more time critical pixel data is processed in real time using a dedicated hardware processor operating under the control of the CPU. The improved digital video processor is adaptable to process subvideo data being supplied in different data formats.

Abstract: A reduced instruction set CPU is programmed to provide software-controlled task management, a stack, and to manage virtual instruction memory. The CPU performs a task management procedure in which the CPU repeatedly checks task flags, and if a task flag is set, performs the task associated with the set task flag. If multiple task flags are set, the highest priority task of those associated with set task flags is performed. Whenever a subroutine call is needed, the subroutine call is implemented by calling a stack management routine. The stack management routine retrieves and stores a return address into a location in DRAM identified by a stack pointer, increments the stack pointer, and then executes a CALL instruction, causing program execution to sequence to the desired subroutine.

Abstract: A decoding circuit for decoding (or decompressing) compressed video data includes an RL circuit, such as MPEG encoded video data. The RL circuit includes a buffer memory for storing run-level pairs during the decoding process. Because the buffer memory in the RL circuit can store ran-level pairs, Huffman-decoding and header decoding, performed by a variable length decoding (VLD) circuit, is decoupled from inverse discrete transform decoding, performed by an IDCT circuit. This decoupling speeds up the decoding pipeline by allowing more continuous operation by both the VLD and IDCT circuits.