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sub-band coding WITH ADAPTIVE BIT ALLOCATION

SIGNAL PROCESSING 1980年第1期2卷 23-30页

作者： GRAUEL, C Institut für Nachrichtentechnik of the Technische Universität Braunschweig Federal Republic of Germany

The paper presents an efficient method for speech encoding which is based on the well known idea of sub-band coding. Typically, the frequency range from 0.3 kc/s to 3.4 kc/s is split into four sub-bands, and the sub-band signals are encoded separately with different accuracies by means of familiar PCM techniques. An adaptive bit allocation scheme is introduced here, in order to replace the usual form of a fixed distribution of the bit rate among the sub-bands. Listening tests have shown that by these means the bit rate can be reduced by more than 2.5 kb/s without degrading speech quality. Accordingly, highly intelligible reproduction of speech is possible at bit rates below 7 kb/s. Zusammenfassung Es wird ein Verfahren zur wirksamen Codierung von Sprachsignalen vorgestellt, welches auf dem wohlbekannten Prinzip der Teilband-Codierung (“sub-band coding”) beruht. Typischerweise wird dabei der Frequenzbereich von 0,3 kHz bis 3,4 kHz in vier Teilbänder aufgespalten, und die Teilbandsignale werden durch geläufige PCM-Verfahren getrennt voneinander mit unterschiedlicher Genauigkeit codiert. Hier wird nine adaptive Bitzuweisung vorgesehen, die die übliche feste Aufteilung der Bitrate auf die verschiedenen Teilbänder ersetzen soll. Hörversuche haben gezeigt, daß durch diese Maßnahme ohne Verringerung der Sprachqualität die Bitrate um mehr als 2,5 kbit/s gesenkt werden kann. Demgemäß ist eine gut verständliche Sprachwiedergabe bei Bitraten unter 7 kbit/s möglich.

关键词： Speech processing sub-band coding bit allocation subjective evaluation

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Adaptive-Differential-Evolution-Based Design of Two-Channel Quadrature Mirror Filter Banks for sub-band coding and Data Transmission

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IEEE TRANSACTIONS ON SYSTEMS MAN AND CYBERNETICS PART C-APPLICATIONS AND REVIEWS 2012年第6期42卷 1613-1623页

作者： Ghosh, Pradipta Das, Swagatam Zafar, Hamim Jadavpur Univ Dept Elect & Telecommun Engn Kolkata 700032 India Indian Stat Inst Elect & Commun Sci Unit Kolkata 700108 India

This paper proposes an improved and adaptive variant of the differential evolution algorithm for the design of two-channel quadrature mirror filters with linear phase characteristics. To match the ideal system response characteristics, the algorithm is employed to optimize the values of the filter bank coefficients. The filter response is optimized in both passband and stopband. The overall filter bank response aims at minimizing objectives like reconstruction error, mean square error in passband, and mean square error in stopband. Effective designing can be achieved by efficiently minimizing the objective function. The proposed algorithm is able to perform better than the other existing design methods. Five different design examples are presented to validate the effectiveness of the proposed approach over other conventional design techniques, as well as state-of-the-art evolutionary algorithms found in the literature.

关键词： Differential evolution (DE) filter banks perfect reconstruction quadrature mirror filter (QMF) sub-band coding

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EXTENSION OF FINITE LENGTH SIGNALS FOR sub-band coding

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SIGNAL PROCESSING 1989年第2期17卷 161-168页

作者： KARLSSON, G VETTERLI, M Department of Electrical Engineering and Center for Telecommuncations Research Columbia University New York NY 10027-6699 U.S.A.

Some problems associated with sub-band coding of images are investigated. The filtering operations needed for splitting an input into different frequency bands, as well as their reconstruction, require an extension beyond the length of the finite signal. If not properly made, the necessary signal extension can yield distortion of the reconstructed signal, and it may complicate the compression of high-pass frequency bands. Five different methods of signal extensions have been investigated for sub-band coding. It turns out that extending the signal so that continuity is maintained may be a sufficient remedy, as shown in an image coding example. Zusammenfassung In diesem Artikel beschäftigen wir uns mit einigen Teilproblemen bei der subbandcodierung von Bildern. Die Filteroperationen, die für die Aufspaltung des Bildes in mehrere Frequenzbänder wie auch für die zugehörige Rekonstruktion gebraucht werden, benötigen Signalwerte jenseits der Grenzen des finiten Bildsignales. Die notwendige Ergänzung des Signals kann Nebeneffekte zur Folge haben, wie z.B. die Verzerrung des rekonstruierten Signals, und sie kann die Komprimierung der höheren Frequenzbänder erschweren. Wir haben insgesamt fünf verschiedene Methoden der Erweiterung des Signals über die Bildgrenzen hinaus unter dem Gesichtspunkt der subbandcodierung untersucht und die zwei genannten Nebenwirkungen in Betracht gezogen. Wie sich zeight, genügt es, bei der Erweiterung des Bildsignals die Kontinuität sicherzustellen; dies wird an einem praktischen Beispiel zur Bildcodierung demonstriert.

关键词： sub-band coding image compression signal extrapolation

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NONLINEAR QUANTIZATION OF SPECTRAL SHAPE IN sub-band coding

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ELECTRONICS LETTERS 1989年第8期25卷 550-552页

作者： VARMA, V LIN, DW DIXON, JL Bell Commun. Res. Inc. Red Bank NJ USA

The authors propose nonlinear quantisation of the spectral shape in sub-band coding. This computationally simple method is shown to yield substantial improvement in speech quality. The performance improvement obtained... 详细信息

关键词： 16 kbit/s 16-band 8-band decoding decoding encoding encoding nonlinear quantisation performance improvement signal processing signal processing spectral shape speech analysis and processing speech processing speech quality sub-band coding subband coding

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An improved optimal bit allocation method for sub-band coding

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PATTERN RECOGNITION LETTERS 2003年第16期24卷 3007-3013页

作者： Wang, Z Lee, Y Leung, CS Wong, TT Zhu, YS Shanghai Jiao Tong Univ Dept Biomed Engn Shanghai 200030 Peoples R China City Univ Hong Kong Dept EE Hong Kong Hong Kong Peoples R China Chinese Univ Hong Kong Dept CSE Hong Kong Hong Kong Peoples R China

This paper presents an improved optimal bit allocation method for sub-band coding. To speed up the allocation process. a coarse bit range for each sub-band is firstly obtained using the log-variance method, and then an optimal searching routine is applied to produce the final solution. Good features are showed in the simulations for evaluating the proposed method. (C) 2003 Elsevier B.V. All rights reserved.

关键词： bit allocation sub-band coding bisection method

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sub-band coding of hexagonal images

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SIGNAL PROCESSING-IMAGE COMMUNICATION 2021年 99卷 116494-116494页

作者： Rashid, Md Mamunur Alim, Usman R. Seequent Calgary AB Canada Univ Calgary Dept Comp Sci Calgary AB Canada

According to the circle-packing theorem, the packing efficiency of a hexagonal lattice is higher than an equivalent square tessellation. Consequently, in several contexts, hexagonally sampled images compared to their Cartesian counterparts are better at preserving information content. In this paper, novel mapping techniques alongside the wavelet compression scheme are presented for hexagonal images. Specifically, we introduce two tree-based coding schemes, referred to as SBHex (spirally-mapped branch-coding for hexagonal images) and BBHex (breadth-first block-coding for hexagonal images). Both of these coding schemes respect the geometry of the hexagonal lattice and yield better compression results. Our empirical results show that the proposed algorithms for hexagonal images produce better reconstruction quality at low bits per pixel representations compared to the tree-based coding counterparts for the Cartesian grid.

关键词： Hexagonal image processing Multiresolution analysis sub-band coding Tree-based wavelet compression

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Shannon Wavelet Approach to sub-band coding

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International Journal of Wavelets, Multiresolution and Information Processing 2003年第2期1卷 233-242页

作者： Charles K. Chui Jianzhong Wang Department of Mathematics & Computer Science University of Missouri-St.Louis St. Louis MO 63121 USA Department of Mathematics and Statistics Sam Houston State University Huntsville TX 77341 USA

It is well known that the Shannon Sampling Theorem allows us to fully recover a continuous-time bandlimited signal from its digital samples, as long as the sampling rate to be chosen is not smaller than the Nyquist frequency. This theory applies to all bandlimited signals, which may or may not occupy the entire frequency band. Hence, it is intuitively convincing that for continuous-time signals, such as those in speech, that do not fully utilize the entire frequency intervals, less digital samples are required for their full recovery. Current techniques in sub-band coding are used for achieving this goal. The objective of this paper is to present a wavelet theory for establishing the mathematical foundation of this sub-band coding approach. A wavelet packet decomposition of the signal provides the optimal sub-band coding bit-rate by using the Shannon wavelet library introduced in this paper.

关键词： Sampling theorem Shannon wavelet sub-band coding wavelets wavelet packets

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Optimum partition of frequency bands in 2-dimensional sub-band image coding

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART III-FUNDAMENTAL ELECTRONIC SCIENCE 1998年第9期81卷 83-94页

作者： Kameda, M Ohtake, K Miyahara, M Japan Adv Inst Sci & Technol Tatsunokuchi Japan Hosei Univ Coll Engn Koganei Tokyo 184 Japan

This paper aims to attain high-efficiency sub-band coding of image signals. We present a theoretical study concerning the optimum partition of the 2-dimensional frequency domain obtained by matching the statistical properties, i.e., the auto-correlation function. Initially, a theoretical model is proposed for an arbitrary 2-dimensional band partition and the corresponding filter bank structure. The relation between the sub-band of the analysis filter bank and the output rate is analyzed based on this model. We assume that each sub-band signal after partition is scalar-quantized and present a theoretical expression that determines the optimum band partition and the bit assignment to the sub-band on the 2-dimensional frequency domain, under the following conditions. (1) The bit rate that is assigned to the input signal is held constant. (2) The quantization noise power in the signal reconstructed at the receiving end is minimized. We present an algorithm for numerical computation in order to derive exactly the optimum partition and the optimum bit assignment. Finally, a 2-dimensional first-order Markov signal sequence whose correlation coefficient between adjacent pixels is close to unity is assumed. The result of numerical computation for the optimum partition and the optimum bit assignment based on the proposed theory are compared to those obtained by the conventional band partition method and the effectiveness of the proposed method is quantitatively verified. (C) 1998 Scripta Technica, Electron Comm Jpn Pt 3, 81(9), 83-94, 1998.

关键词： sub-band coding 2-dimensional frequency domain quantization noise power optimum frequency band partition wavelet transform

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Application of biorthogonal wavelet transform to the compression of ultraviolet-visible spectra

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COMPUTERS & CHEMISTRY 1999年第1期23卷 85-96页

作者： Ho, HL Cham, WK Chau, FT Wu, JY Hong Kong Polytech Univ Union Lab Asymmetr Synth Hong Kong Peoples R China Hong Kong Polytech Univ Dept Appl Biol & Chem Technol Hong Kong Peoples R China Chinese Univ Hong Kong Dept Elect Engn Hong Kong 100083 Peoples R China

A wavelet transform (WT) based method was proposed to compress ultraviolet-visible (UV-vis) spectra from chemical and biochemical studies. These spectra were first transformed into different sub-bands which contain information on different scales and frequency bands. The biorthogonal filter banks (BFB) coupled with the circular (CE) or symmetric extension (SE) method were employed in the WT treatment. Differential pulse code modulation (DPCM) was applied to further reduce the storage space required for the scale coefficients which were generated from the WT treatment. Then, optimal bit allocation (OBA) procedure for data quantization coupled with variable length coding (VLC) was applied to these coefficients to minimize the root-mean-square difference (RMSD) between the original and reconstructed spectra. Both synthetic and experimental spectra were used in the study. Our results show that the performance of the proposed compression methods are better than those suggested in the previous studies. (C) 1999 Elsevier Science Ltd. All rights reserved.

关键词： wavelet transform biorthogonal filter bank sub-band coding optimal bit allocation variable length coding data compression

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Design of two-channel quadrature mirror filter bank using particle swarm optimization

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DIGITAL SIGNAL PROCESSING 2010年第2期20卷 304-313页

作者： Upendar, J. Gupta, C. P. Singh, G. K. Indian Inst Technol Dept Elect Engn Roorkee Uttarakhand India

In this paper, a particle swarm optimization (PSO) is used to design the quadrature mirror filter (QMF) banks with linear phase in frequency domain. A unique PSO is developed to optimize filter bank coefficients to match the ideal system response. The three main attributes used in assessing the performance of filter are reconstruction error. mean square error in pass band and mean square error in stop band. The proposed PSO based method produces almost the same result as that of the existing methods. As compared to the existing methods this method is very simple to implement for the QMF bank optimization. To implement the proposed PSO algorithm, a Matlab program is developed and three examples have been presented to illustrate the performance of the proposed method. (C) 2009 Elsevier Inc. All rights reserved.

关键词： Quadrature mirror filter bank sub-band coding Perfect reconstruction

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