In the paper, an autocorrelation-based pitch determination algorithm (PDA) is described. Realtime implementation on TMS32020/C25 digital signal processors is considered. Several optimizations and variations of autocor...
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In the paper, an autocorrelation-based pitch determination algorithm (PDA) is described. Realtime implementation on TMS32020/C25 digital signal processors is considered. Several optimizations and variations of autocorrelation PDAs have been implemented on a single TMS32020-based system. The algorithms are primarily designed with TMS32020/C25 LPC vocoders in mind and combine high speed, good performance and flexibility.
General Instrument's DigiCipher(TM) System is an all digital HDTV system that can be transmitted over a single 6 MHz VHF or UHF channel. It provides full HDTV performance with virtually no visible transmission imp...
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General Instrument's DigiCipher(TM) System is an all digital HDTV system that can be transmitted over a single 6 MHz VHF or UHF channel. It provides full HDTV performance with virtually no visible transmission impairments due to noise, multipath, and interference. It offers high picture quality, while the complexity of the decoder is low. Furthermore, low transmitting power can be used, making it ideal for simulcast HDTV transmission using unused or taboo channels. The DigiCipher(TM) HDTV System can also be used for cable and satellite transmission of HDTV. There is absolutely no satellite receive dish size penalty (compared to FM-NTSC) in the satellite delivery of DigiCipher(TM) HDTV. This is important not only for DBS, but for broadcast and cable since broadcast network and cable programming is typically delivered to affiliates via satellite. To achieve the full HDTV performance in a single 6 MHz bandwidth, a highly efficient unique compression algorithm based on DCT transform coding is used. Through the extensive use of the computer simulation, the compression algorithm has been refined and optimized. Computer simulation results show excellent video quality for a variety of HDTV material. For error free transmission of the digital data, powerful error correction coding combined with adaptive equalization is used. At a carrier-to-noise ratio of above 19 dB, essentially error free reception can be achieved.
A technique developed to reduce the transmission requirements of facsimile images while maintaining high intelligibility in mobile communications environments is described. The technique is based on the implementation...
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A technique developed to reduce the transmission requirements of facsimile images while maintaining high intelligibility in mobile communications environments is described. The technique is based on the implementation of a low-cost interface unit suitable for facsimile communication between low-power mobile stations and fixed stations for both point-to-point and point-to-multipoint transmissions. The interface may be colocated with the transmitting facsimile terminal equipment and functions in conjunction with standard Group 3 facsimile terminals. Although the technique was implemented and tested by intercepting facsimile documents in a store-and-forward mode, the algorithms developed operate on a small number of scan lines, thus lending themselves to potential real-time operation over data channel rates ranging from 2400 to 800 b/s, and user-to-interface transmission rates from 9600 to 2400 b/s respectively.< >
The authors discuss textural substitution methods. They present a massively parallel architecture for textural substitution that is based on a systolic pipe of 3839 identical processing elements that forms what is ess...
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The authors discuss textural substitution methods. They present a massively parallel architecture for textural substitution that is based on a systolic pipe of 3839 identical processing elements that forms what is essentially an associative memory for strings that can learn new strings on the basis of the text processed thus far. The key to the design of this architecture is the formulation of an inherently top-down serial learning strategy as a bottom-up parallel strategy. A custom VLSI chip for this architecture that is capable of operating at 320-Mb/s has passed all simulations and is being fabricated with 1.2- mu m double-metal technology.< >
A recursive preprocessing approach to transform-based medical image compression is presented. This preprocessing approach, combined with the cas-cas transform, shows good performance when applied to medical magnetic r...
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A recursive preprocessing approach to transform-based medical image compression is presented. This preprocessing approach, combined with the cas-cas transform, shows good performance when applied to medical magnetic resonance images (MRIs). Overall, recursive preprocessing significantly improved all transform-based compression schemes tested, with more improvement noted in the fast cas-cas transform (FCCT) than in the fast cosine transform (FCT). By performing a recursive preprocessing step in the space domain before transforming, edge discontinuities are reduced so that energy packing efficiency can be higher. By using the FCCT, a speed advantage is obtained as compared to the commonly used FCT. The preliminary results show that the compression algorithm using the cas-cas transform affords both a higher compression ratio and speedier computation than the conventional cosine transform.< >
A codec for digital transmission of HDTV signals designed to operate with the 1125/60 and 1250/50 interlaced studio systems is described. The codec is based on the application of discrete cosine transforms (DCT), comb...
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A codec for digital transmission of HDTV signals designed to operate with the 1125/60 and 1250/50 interlaced studio systems is described. The codec is based on the application of discrete cosine transforms (DCT), combined with temporal differential pulse-code modulation (DPCM) on blocks of 8*8 samples for both luminance and color differences. The line bit rate can range from a minimum of about 60 Mb/s up to more than 140 Mb/s. This range includes the standard digital CCITT hierarchies of 2*34 Mb/s, 2*45 Mb/s, and 140 Mb/s. For higher bit rates the full studio quality (1920 pixels/line) can be transmitted, while for lower bit rates, a horizontal resolution of about 1440 pixels/line is a better compromise, in order not to stress the compression algorithm. Applications of the codec to various transmission links, including satellite transmission, are discussed.< >
Source-dependent channel-error codes for speech compression algorithms are obtained by minimizing an appropriate speech distortion criterion under channel-error conditions. A simulated annealing algorithm for optimizi...
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Source-dependent channel-error codes for speech compression algorithms are obtained by minimizing an appropriate speech distortion criterion under channel-error conditions. A simulated annealing algorithm for optimizing such a criterion is described. The resulting channel codes are efficient since they provide error correction of nonuniform accuracy (highly probable quantization levels receive more accurate correction) and/or nonuniform error detection (serious errors are more likely to be detected). An optimal tradeoff between error correction and error detection (associated with a recovery procedure) is obtained. Any desired fraction of the codewords can be allocated for error protection, including noninteger bit allocations. The performance of the source-dependent channel-coding technique is reported for the code-excited linear prediction (CELP) algorithm.< >
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