Abstract: Dynamic varying of encrypting of a stream of data at an encryption unit based on data content is disclosed. The dynamic varying of the encrypting, which can be responsive to passage of a predefined number of units of physical data or passage of a predefined number of conceptual units of data, is accomplished by changing at least one encryption parameter over different portions of the data. The at least one encryption parameter can comprise one or more of an encryption key, an encryption granularity, an encryption density scale, an encryption density, an encryption delay, an encryption key update variable, and an encryption key update data trigger. The change in encryption parameter is signaled to a receiver's decryption unit and used by the decryption unit in decrypting the dynamically varied encrypted stream of data. The stream of data may comprise, e.g., MPEG compressed video or audio.

Abstract: In encoding and decoding video signals, a progressive video bitstream is received which has reference frames and non-reference frames, each having an initial temporal reference in accordance with an initial frame sequence structure. The temporal references of the only the reference frames are remapped, by ignoring the non-reference frames. The reference frames are packetized with a base packet-identifier (PID) and the non-reference frames with an enhancement PID, to provide base and enhancement transport bitstreams, respectively.

Abstract: A method and mechanism for repositioning video images in a compressed data stream without requiring bit shifting. A P frame image is to be repositioned from an original position to an alternate position. The P frame image data is analyzed to determine whether the repositioning will result in the image data bit positions being changed with respect to the original image. In response to determining the bit positions will be changed, the original image data is modified by adding stuffing bits in the form of a stuffing macroblock to restore the image data to its original bit positions. The P frame is intra-coded and the stuffing macroblock is non-intra coded. A non-intra quantization matrix is selected such that upon decode the stuffing macroblock data does not adversely affect the final picture. Maintaining the original bits positions of the image data facilitates a straightforward copy of unmodified data from the original P frame to the new P frame.

Abstract: Copy protection is provided at a mass storage device provided in or connected to a decoder for receiving digital transmissions of audio and video program material by virtual scrambling of blocks of data. Non-sequential storage locations for blocks of data are defined in accordance with a key and the file allocation table is encrypted and stored. Thus blocks of data remain intact and need not be decrypted upon playback, reducing processing time, while the program is effectively protected from reassembly without decryption of the file allocation table. The key(s) may be maintained internally within the decoder and need not be shared, thus avoiding a need for user identification and/or authentication. Software for encryption, including keys may be downloaded to the decoder through the same transmission link used for transmission of data files that may be encrypted in response to control signals or flags transmitted with data files to be protected.

Abstract: Two data streams derived from a transmitted data stream are remultiplexed with a coarser granularity for storage in data blocks which assure that corresponding portions of each of the two data streams are made available in the same data block. The data streams are buffered in queues from which sub-blocks are transferred as buffer sections having sizes corresponding to relative bit rates therein in the order the sub-blocks are filled, preferably using bytes to interrupt processing. Thus, the sub-blocks will be grouped into data blocks in accordance with the correspondence of the data streams such as the time correspondence of audio and video data. As applied to digital video data transmissions, a system time clock (STC) value is stored in a sub-block header and/or a data block header and, using a look-up table or other arrangement for estimating a storage location, a data block can be retrieved from storage in accordance with a target STC value.

Abstract: A method and mechanism for repositioning video images in a compressed data stream without requiring bit shifting. A P frame image is to be repositioned from an original position to an alternate position. The P frame image data is analyzed to determine whether the repositioning will result in the image data bit positions being changed with respect to the original image. In response to determining the bit positions will be changed, the original image data is modified by adding stuffing bits in the form of a stuffing macroblock to restore the image data to its original bit positions. The P frame is intra-coded and the stuffing macroblock is non-intra coded. A non-intra quantization matrix is selected such that upon decode the stuffing macroblock data does not adversely affect the final picture. Maintaining the original bits positions of the image data facilitates a straightforward copy of unmodified data from the original P frame to the new P frame.

Abstract: Data corrupted or lost in transmission over a lossy digital transmission link is replaced and/or omitted from data presented in connection with storage to and read out from a mass storage device. Different procedures are used to conceal artifacts corresponding to errored data based upon valid data preceding and following the error in a data stream and a size of the error.

Abstract: An image processor produces a DPCM prediction error to be quantized. If the prediction error value is positive, the value passes unchanged to a quantizer. If the prediction error value is negative, a bias value is added to the prediction error value to produce a positive number within the operating limits of the quantizer. Biased prediction error values are quantized. Because all values received by the quantizer are positive and within the current quantizer limits, the quantization table used by the quantizer need not include quantization values for negative prediction error values. This reduces the scope of prediction error values by a factor of two, doubling quantization resolution.

Abstract: An MPEG coded and compressed video signal is received and decompressed for display. Prior to storing frames required for motion compensation in memory, pixel blocks are recompressed into DPCM prediction error values to reduce bandwidth and frame memory requirements. Fixed length quantization and dequantization tables (FIG. 2) have N levels (e.g., 15 levels), and each level has an associated output symbol of predominantly M bits (e.g., 4 bits), except that at least one of said N levels (e.g., level 7) is defined by a unique short symbol having less than M bits (e.g., 3 bits), and input data for that level is received at a desired rate. Each time a short symbol is used to represent a data value, bandwidth and memory are reduced and/or preserved for other uses, for example, inserting overhead data into a fixed-size data stream. For large sequences of data, such as exists for video data for example, the reduction in memory and bandwidth is significant.

Abstract: A memory efficient image processor receives DPCM prediction error values from decompressed MPEG coded digital video signals in the form of pixel blocks containing luminance and chrominance data in a 4:2:2 or 4:2:0 format and recompresses the pixel blocks to a predetermined resolution. Luminance and chrominance data are processed with different compression laws during recompression. Luminance data are recompressed to an average of six bits per pixel, and only a reference pixel and one other pixel are processed separately from all other luminance pixels in a block. Chrominance data are recompressed to an average of four bits per pixel. Each pixel block is stored with overhead information facilitating efficient and accurate reconstruction.

Abstract: Apparatus, method and computer program product are provided for digitally processing an encrypted data stream scrambled, for example, according to content scrambling system (CSS) technology. This digital processing insures against communication of clear data within the computer system from a central processing unit (CPU) to any accessible structure, such as memory or a system bus. Descrambling of the (CSS) scrambled data stream occurs within a module executing on the CPU, which is followed by reencryption of the data prior to transfer from the CPU. By so processing the data, integrity of copyrighted material is maintained, while allowing for software descrambling of the CSS encrypted data stream. Various techniques for establishing the encryption/decryption algorithm pair employed are described. Decryption of the re-encrypted data can occur at a receiving software module and/or a receiving hardware device, such as a decoder.

Abstract: In an MPEG compatible image signal processor an MPEG data stream is decoded, decompressed and recompressed before blocks of image pixel values are stored in memory. The recompression system evaluates block data to determine the range and minimum pixel values for a given image block of pixels values. These values are encoded, and the encoded representations are stored in a parameter field with the quantized data block to facilitate data reconstruction. Encoding occurs by fitting the actual range and minimum values to a predetermined set of values. Each selected predetermined value is then encoded as a three-bit index in the parameter field. Storing the encoded values with the quantized data facilitates reconstruction with minimal error. Also, encoding the values preserves memory for the quantized data.

Abstract: An apparatus and concomitant method for constructing a valid OSD message bitstream from a plurality of stored character bitstreams. Each character of the OSD font set is initially scaled into a fixed block size, e.g., a block size of 16.times.16 pixels. Each character is then encoded into a "character bitstream" using the intra macroblock coding syntax. The character bitstream is stored within a storage medium. When a frame of OSD messages needs to be encoded, the character bitstreams are read from the storage medium and cascaded to form a valid OSD message bitstream which represents the frame of OSD messages.

Abstract: Apparatus, method and computer program product are provided for digitally processing an encrypted data stream scrambled, for example, according to content scrambling system (CSS) technology. This digital processing insures against communication of clear data within the computer system from a central processing unit (CPU) to any accessible structure, such as memory or a system bus. Descrambling of the (CSS) scrambled data stream occurs within a module executing on the CPU, which is followed by re-encryption of the data prior to transfer from the CPU. By so processing the data, integrity of copyrighted material is maintained, while allowing for software descrambling of the CSS encrypted data stream. Various techniques for establishing the encryption/decryption algorithm pair employed are described. Decryption of the re-encrypted data can occur at a receiving software module and/or a receiving hardware device, such as a decoder.

Abstract: An MPEG compatible decoder receives encoded, compressed data in the form of image representative pixel blocks. The decoder includes a frame memory (20) for storing reconstructed pixel blocks incident to the decoding process. The previously decompressed data is re-compressed (30) before being written to the memory. Stored decompressed data is decompressed for display (34, 26), or as needed for decoding functions such as motion compensation processing (32, 22). The compression performed before writing data to memory is block-based compression using compressed data from one of two different compression paths (FIG. 3, 314, 320) which compress a given pixel block simultaneously.

Abstract: A television receiver includes an MPEG decoder for providing decoded pixel blocks. Decoded pixels are recompressed prior to storage in frame memory. In the recompression process a reference first pixel is compressed as a function of a pixel block parameter. A reconstructed reference pixel value is used in a prediction network when reconstructing remaining pixels of the pixel block prior to display. A first pixel processor accurately compresses a reference pixel which prevents the propagation of a prediction error throughout the reconstructed block.

Abstract: A television receiver with an MPEG decoder is configurable for full high definition decoding and display, or reduced cost lower definition display. The MPEG decoder (10-33) uses a controllable dual-mode data reduction network selectively employing horizontal detail reduction (29) and data re-compression (30) between the decoder and the decoder frame memory (20) from which image information to be displayed (27) is derived. The amount of data reduction is manufacturer selected in accordance with the resolution of the display device, e.g., equal to or less than high definition resolution. The frame memory size is also manufacturer selected in accordance with the resolution of the display device.

Abstract: A television receiver with an MPEG decoder is configurable for full high definition decoding and display, or reduced cost lower definition display. The MPEG decoder (10-33) uses a controllable dual-mode data reduction network selectively employing horizontal detail reduction (29) and data re-compression (30) between the decoder and the decoder frame memory (20) from which image information to be displayed (27) is derived. The amount of data reduction is manufacturer selected in accordance with the resolution of the display device, e.g., equal to or less than high definition resolution. The frame memory size is also manufacturer selected in accordance with the resolution of the display device.

Abstract: A disclosed method and apparatus reduces the number of computations and simplifies the hardware required to provide compressed video output data. Video input data is converted into input pixel blocks. Best predicted blocks and associated motion vectors are determined for input pixel blocks located in a predetermined area of the image. In addition, candidate predicted blocks are determined for other input pixel blocks. This is done by .extrapolating motion vectors from the previously determined associated motion vectors and identifying candidate predicted blocks using the extrapolated motion vectors. The candidate predicted blocks are mutually compared, and one of the blocks is selected consistent with compression data rate requirements. The selected block is compressed to provide an output block which is formatted into an output data packet.

Abstract: In a video signal processor including a motion compensated predictive coding data compression system, three adjacent image frames (1, 2, 3) are analyzed to detect a luminance gradient such as is typically associated with image fading. The frames are similarly divided into several segments (A . . . L). The sum of the absolute pixel value differences between corresponding segments from adjacent frames is obtained for each of two pairs adjacent frame segments (DIFF.sub.1-2 ; DIFF.sub.2-3). The ratio of the two frame differences (S) is obtained for each segment. Fading is indicated if the ratio remains substantially constant for all or a predetermined number of regions. If fading is detected, any motion vectors generated by the motion coder are assigned a zero value and are not coded.