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International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： R. Viswanathan W. Russell A. Higgins M. Berouti J. Makhoul Bolt Beranek and Newman Inc. Cambridge Mass. Bolt Beranek and Newman 슠Inc. Cambridge MA USA

This paper considers the optimization of speech quality of adaptive predictive coding (APC) systems for transmission over a synchronous 16 kb/s channel. Among the important issues included in this on-going optimization study are: comparative evaluation of several methods for adaptive coding of the APC residual; comparative testing of several methods for adaptive shaping of the spectrum of the quantization noise; and optimization of various parameter values and their bit allocation. In addition to reporting the results from this study, we report on the occurrence of "limit cycles" or regions of excessive quantization noise build-up, offer an explanation for their cause in terms of the feedback gain (or "loop gain") of the APC transmitter, and present experimental results obtained using several remedial means for this problem. Also, we report on the relative properties of different APC coder configurations. Based on the results of our optimization study to date, we present several optimized APC systems.

关键词： Optimization methods Quantization Noise shaping Speech coding Predictive coding adaptive coding Testing Bit rate Limit-cycles Feedback loop

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COMPARATIVE PERFORMANCE OF SVD AND adaptive COSINE TRANSFORM IN coding IMAGES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1979年第8期27卷 1230-1234页

作者： GARGUIR, N Centre National d'Etudes Spatiales Toulouse France

An adaptive coding for singular value decomposition (SVD) samples is described in order to reduce the amount of transmitted data for monochrome images. This method is compared to the discrete cosine transform in terms of mean square error. Low bit rates, as 0.8 bits/pixel, are attempted with a good visual quality and low RMS error (0.087%). The visual and mathematical results of the transmission errors are shown and given.

关键词： Image coding Singular value decomposition Bit rate Discrete transforms Computer errors Entropy adaptive coding Discrete cosine transforms Mean square error methods Satellites

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adaptive coding OF MONOCHROME AND COLOR IMAGES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1977年第11期25卷 1285-1292页

作者： CHEN, WH SMITH, CH FORD AEROSP & COMMUN CORP DIV WESTERN DEV LABSPALO ALTOCA 94303

An efficient adaptive encoding technique using a new implementation of the Fast Discrete Cosine Transform (FDCT) for bandwidth compression of monochrome and color images is described. Practical system application is attained by maintaining a balance between complexity of implementation and performance. FDCT sub-blocks are sorted into four classes according to level of image activity, measured by the total ac energy within each sub-block. Adaptivity is provided by distributing bits between classes, favoring higher levels of activity over lower levels. Excellent performance is demonstrated in terms of mean square error and direct comparison of original and reconstructed images. Results are presented for both noiseless and noisy transmission at a total rate of 1 bit and 0.5 bit per pixel for a monochrome image and for a total rate of 2 bits and 1 bit per pixel for a color image. In every case the total bit rate includes all overhead required for image reconstruction and bit protection.

关键词： adaptive coding Color Image coding Image reconstruction Colored noise Pixel Discrete cosine transforms Bandwidth Energy measurement Mean square error methods

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MULTIPURPOSE HARDWARE FOR DIGITAL coding OF AUDIO SIGNALS

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IEEE TRANSACTIONS ON COMMUNICATIONS 1978年第11期26卷 1785-1788页

作者： JOHNSTON, JD GOODMAN, DJ BELL TEL LABS INC CRAWFORD HILL LABHOLMDELNJ 07733

We describe an adaptive coding system capable of representing audio frequency signals in a wide variety of digital code formats. To provide adaptive quantization, the step size is adjusted by voltage controlled amplifiers operating with analog control signals. Sine wave signal-to-noise ratio measurements demonstrate important relationships among the main code classifications: pcm, apcm, dpcm, adpcm. The multipurpose coder has proved a useful laboratory aid in the design of special purpose coders. After adjustment and evaluation of parameters using the multipurpose coder one proceeds to an economical, specialized design.

关键词： Hardware Size control Voltage control adaptive coding Frequency Programmable control adaptive control Quantization Signal to noise ratio Phase change materials

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adaptive TRANSFORM coding OF SPEECH SIGNALS

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IEEE TRANSACTIONS ON ACOUSTICS SPEECH AND SIGNAL PROCESSING 1977年第4期25卷 299-309页

作者： ZELINSKI, R NOLL, P BELL TEL LABS INC MURRAY HILLNJ 07974 HEINRICH HERTZ INST BERLINFED REP GER

This paper discusses speech coding systems based upon transform coding (TC). It compares several transforms and shows that the cosine transform leads to a nearly optimum performance for almost all speech sounds. Various adaptive coding strategies are then investigated, and a coding scheme is proposed that is based on a nonadaptive discrete cosine transform (DCT), on an adaptive bit assignment, and on adaptive quantization. The adaptation is controlled by a short-term basis spectrum that is derived from the transform coefficients prior to coding and transmission and that is transmitted as side information to the receiver. The main result is that this adaptive transform coder performs better than all known nonpitch-tracking coding schemes; it extends the range of speech waveform coding to lower bit rates and closes the gap between vocoders and predictive waveform coders.

关键词： Transform coding Speech coding Discrete transforms Quantization Acoustic distortion Fast Fourier transforms Signal analysis Digital signal processing adaptive coding Discrete cosine transforms

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SURVEY OF adaptive IMAGE-coding TECHNIQUES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1977年第11期25卷 1275-1284页

作者： HABIBI, A TRW DEF & SPACE SYST GRP REDONDO BEACHCA 90274

The following is a survey of the technical literature on adaptive coding of imagery. Section 1 briefly discusses the general problem of image data compression. The optimum image data compression system, from a theoretical viewpoint, is presented in Section 1.1. The theoretical and the implementational problems of the optimum system are discussed and the assumptions that are made to overcome these problems are outlined. One important assumption is the stationarity which is not true for most imagery. In adaptive systems the parameters are varied according to changes in signal statistics optimizing the system performance for nonstationary signals. In this article the adaptive systems are divided to four categories. Section 2 is a survey of adaptive transform coding systems. Section 3 discusses adaptive predictive coding systems. Sections 4 and 5 discuss adaptive cluster coding and adaptive entropy technique, respectively.

关键词： Image coding Karhunen-Loeve transforms adaptive systems Data compression Image converters adaptive coding Entropy Image sampling Quantization Autocorrelation

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REFERENCE ENcoding OF CORRELATED DIGITAL SOURCES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1978年第1期26卷 156-161页

作者： MARK, JW DASIEWICZ, PP UNIV WATERLOO COMP COMMUN NETWORK GRP WATERLOO N2L 3G1 ONTARIO CANADA

A reference code, with an associated bound on the code rate, for the encoding of correlated digital sources is introduced. The reference code is adaptive and simple to implement. Image coding results obtained using concatenated trellis and reference encoding are presented. For the images studied, the reference code attains an average code rate of approximately 0.64 bits/bit, or a reduction in information rate of approximately 36%.

关键词： Encoding Image coding Source coding Concatenated codes Information rates adaptive coding Research and development Memory Books Embryo

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OPTIMUM RUN LENGTH CODES

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IEEE TRANSACTIONS ON COMMUNICATIONS 1974年第6期CO22卷 826-835页

作者： MEYR, H ROSDOLSKY, HG HUANG, TS HASLER LTD RES DIV BERN SWITZERLAND PURDUE UNIV DEPT ELECT ENGN LAFAYETTE IN USA SCI CONTROL SYST LTD ESSEN WEST GERMANY

To realize the full redundancy reducing potential of run length coding over a collection of picture segments with varying run length statistics, adaptive coding techniques have been proposed. This paper compares results for a previously proposed A -code, for which the block length was varied adaptively, with those obtained using a fixed block length B -code first proposed here. Both codes use variable length codewords integrally related to the code block length. For all pictures analyzed, the fixed block length B -code performed nearly as well as the adaptive A -code. For both, the bit rates were close to the entropy bound. The reasons for these results are discussed. It is Shown that, due to the prevalence of exceptionally long runs, the A -code, which is nearly optimal for exponentially distributed run lengths, performs poorly for actual pictures unless the block length is varied adaptively. The strategy used to implement the A-code adaptively is described. The optimal block length of the B-code,on the other hand, is shown to be largely independent of the picture statistics and need therefore not be varied adaptively. The hardware implementation of both coding techniques, the influence of channel disturbances on image quality, and the problems of error correction and line synchronization are discussed.

关键词： Redundancy Statistics adaptive coding Performance analysis Bit rate Entropy Statistical distributions Hardware Image coding Image quality

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NEW CRITERION FOR TESTING ANALOG-TO-DIGITAL CONVERTERS FOR STATISTICAL EVALUATION

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IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 1973年第3期IM22卷 214-217页

作者： KOLLER, HU SWISS FED INST TECHNOL ZURICHSWITZERLAND

The influence of linearity errors on the statistical properties of analog-to-digital converter (ADC) outputs is discussed. It is shown that most ADCs available on the market cannot be used for precise statistical measurements. A measurement technique and an error definition is proposed to allow a careful evaluation of ADCs for statistical measurements.

关键词： Testing Analog-digital conversion Linearity Feedback Frequency conversion Measurement techniques Programmable control adaptive control Information processing adaptive coding

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ERROR CORRECTION CODE PERFORMANCE ON HF, TROPOSCATTER, AND SATELLITE CHANNELS

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IEEE TRANSACTIONS ON COMMUNICATION TECHNOLOGY 1971年第5期CO19卷 781-&页

作者： BRAYER, K MITRE Corporation Bedford MA USA

Four forward error correction techniques are examined and their performance compared on several real channels. Techniques of both adaptive and nonadaptive block and convolutional coding are examined. The Golay code is considered in a randomerror correcting mode and in an adaptive burst-random modes. Both versions employ interleaving as an added error correction aid. The adaptive convolutional code is a diffuse threshold-decoded Gallager code requiring a variable guard space, while the nonadaptive is a Massey code. The codes are commonly used rate 1/2 codes. The codes are evaluated and compared on three channels: a transcontinental HF 4800 bit/s channel between San Diego, Calif., and Bedford, Mass.; a mixed wireline microwave troposcatter 2400 bit/s channel dominated by a 583-mi troposcatter hop; and a 2400 bit/s satellite communications circuit from Ascension Island to Andover, Me., with wireline transmission from Andover, Me., to Greenbelt, Md. All three channels exhibit burst errors with the error rate decreasing and the burst error density increasing in the order in which channels were identified. The adaptive codes are shown to perform better than nonadaptive codes, although the difference is less significant for convolutional codes. Furthermore, the convolutional codes give better performance than nonconcatenated block codes.

关键词： Error correction codes Hafnium Convolutional codes Forward error correction Interleaved codes Satellite communication Microwave circuits Error analysis adaptive coding Block codes

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