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  • 11
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    More About Vector Adaptive/Predictive Coding Of Speech (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Report presents additional information about digital speech-encoding and -decoding system described in "Vector Adaptive/Predictive Encoding of Speech" (NPO-17230). Summarizes development of vector adaptive/predictive coding (VAPC) system and describes basic functions of algorithm. Describes refinements introduced enabling receiver to cope with errors. VAPC algorithm implemented in integrated-circuit coding/decoding processors (codecs). VAPC and other codecs tested under variety of operating conditions. Tests designed to reveal effects of various background quiet and noisy environments and of poor telephone equipment. VAPC found competitive with and, in some respects, superior to other 4.8-kb/s codecs and other codecs of similar complexity.
    Keywords: ELECTRONIC SYSTEMS
    Type: NPO-18297 , NASA Tech Briefs (ISSN 0145-319X); 16; 11; P. 68
    Format: text
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    NASA TECHNICAL REPORTS
  • 12
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    Vector Adaptive/Predictive Encoding Of Speech (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Vector adaptive/predictive technique for digital encoding of speech signals yields decoded speech of very good quality after transmission at coding rate of 9.6 kb/s and of reasonably good quality at 4.8 kb/s. Requires 3 to 4 million multiplications and additions per second. Combines advantages of adaptive/predictive coding, and code-excited linear prediction, yielding speech of high quality but requires 600 million multiplications and additions per second at encoding rate of 4.8 kb/s. Vector adaptive/predictive coding technique bridges gaps in performance and complexity between adaptive/predictive coding and code-excited linear prediction.
    Keywords: ELECTRONIC SYSTEMS
    Type: NPO-17230 , NASA Tech Briefs (ISSN 0145-319X); 13; 9; P. 40
    Format: text
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    NASA TECHNICAL REPORTS
  • 13
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    Systolic architectures for vector quantization (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A family of architectural techniques are proposed which offer efficient computation of weighted Euclidean distance measures for nearest-neighbor codebook searching. The general approach uses a single metric comparator chip in conjunction with a linear array of inner product processor chips. Very high vector-quantization (VQ) throughput can be achieved for many speech and image-processing applications. Several alternative configurations allow reasonable tradeoffs between speed and VLSI chip area required.
    Keywords: COMPUTER OPERATIONS AND HARDWARE
    Type: IEEE Transactions on Acoustics, Speech, and Signal Processing (ISSN 0096-3518); 36; 1651-166
    Format: text
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    NASA TECHNICAL REPORTS
  • 14
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    A prototype 4800 bps voice terminal for the mobile satellite experiment (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The authors report the final stage of a research project for the NASA mobile satellite experiment (MSAT-X). The work has resulted in two alternative coding techniques which have achieved good communications quality at 4.8 kb/s while tolerating vehicle noise, fading, and a fairly high-error-rate, bursty channel. The authors have constructed a circuit board based on three AT&T 32-bit floating-point DSP32 digital signal processors (DSP) and providing both excess processing power and considerable flexibility for handling different variations of the algorithms. A Motorola 68HC11 microcomputer chip serves as the board controller and interface handler. Mounted on a wirewrapped card, the prototype's circuit footprint amounts to only 225 cm2 and consumes about 13 W of power. A description is given of the architecture, signal processing and communication functions, circuitry, and firmware of the prototype. Issues such as synchronization, framing, error control, and modem interface are also addressed.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: GLOBECOM ''87 - Global Telecommunications Conference; Nov 15, 1987 - Nov 18, 1987; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 15
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    Vector excitation coding with dynamic bit allocation (1988)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Vector excitation coding (VXC) has shown promise for digital transmission of fairly high communications quality speech at low bit rates, but current version of the algorithm still suffer from audible degradations, particularly at 4.8 kb/s. The authors examine the technique of dynamic bit allocation (DBA) to improve the performance of VXC for a given bit rate. The approach is based on the observation that the minimum bit rate needed to code adequately both the long-term and short-term predictors in VXC varies dynamically with time. Therefore, in frames where fewer bits suffice for the predictors, the unneeded bits can be reallocated to other coder parameter sets such as excitation vectors. By dynamically distributing available bits among the different coder parameter sets while keeping the total number of bits in each frame fixed, it is possible to improve overall coder performance without increasing bit rate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: GLOBECOM ''88 - IEEE Global Telecommunications Conference and Exhibition; Nov 28, 1988 - Dec 01, 1988; Hollywood, FL; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 16
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    Pulse Vector-Excitation Speech Encoder (1989)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Proposed pulse vector-excitation speech encoder (PVXC) encodes analog speech signals into digital representation for transmission or storage at rates below 5 kilobits per second. Produces high quality of reconstructed speech, but with less computation than required by comparable speech-encoding systems. Has some characteristics of multipulse linear predictive coding (MPLPC) and of code-excited linear prediction (CELP). System uses mathematical model of vocal tract in conjunction with set of excitation vectors and perceptually-based error criterion to synthesize natural-sounding speech.
    Keywords: ELECTRONIC SYSTEMS
    Type: NPO-17131 , NASA Tech Briefs (ISSN 0145-319X); 13; 11; P. 34
    Format: text
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    NASA TECHNICAL REPORTS
  • 17
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    Vector excitation speech or audio coder for transmission or storage (1989)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: A vector excitation coder compresses vectors by using an optimum codebook designed off line, using an initial arbitrary codebook and a set of speech training vectors exploiting codevector sparsity (i.e., by making zero all but a selected number of samples of lowest amplitude in each of N codebook vectors). A fast-search method selects a number N.sub.c of good excitation vectors from the codebook, where N.sub.c is much smaller tha ORIGIN OF INVENTION The invention described herein was made in the performance of work under a NASA contract, and is subject to the provisions of Public Law 96-517 (35 USC 202) under which the inventors were granted a request to retain title.
    Keywords: Communications and Radar
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 18
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    Photoacoustic Effect with Solids: A Theoretical Treatment (1975)
    American Association for the Advancement of Science
    Details
    Publication Date: 1975-11-07
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science
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    PAPER CURRENT
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