In low rate code-excited linearpredictive (CELP) coders, the LPC spectral information is usually quantized and transmitted on a frame-by-frame basis about every 20 to 30 msec. The quality of speech reproduced by a CE...
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In low rate code-excited linearpredictive (CELP) coders, the LPC spectral information is usually quantized and transmitted on a frame-by-frame basis about every 20 to 30 msec. The quality of speech reproduced by a CELP coder can be improved by making spectral transitions as smooth and continuous as possible. One way In which this can be accomplished without increasing the transmission bit rate is to interpolate the LPC spectral parameters between adjacent extraction frames. This, however, usually leads to a dramatic increase in the computations required for the codebook search. In this study, we have developed a new LPC interpolation technique, based on interpolating the impulse response of the LPC synthesis filter. We demonstrate that this method offers a significant complexity reduction for the codebook search over other typical interpolation schemes. Furthermore, our experiments show that the coder using the impulse response for interpolation produces the same speech quality as the coder using the LSP parameters for interpolation, and both these parameter sets are superior to other LP representations for interpolation.
We provide a simple proof of the minimum phase property of the optimum linear prediction polynomial, The proof follows directly from the fact that the minimized prediction error has to satisfy the orthogonality princi...
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We provide a simple proof of the minimum phase property of the optimum linear prediction polynomial, The proof follows directly from the fact that the minimized prediction error has to satisfy the orthogonality principle, Additional insights provided by this proof are also discussed.
Sukkar et al. defined the function zinc (t) = A sinc (t) + B cosc (t). It is pointed out that the terms sinc (t) and cosc (t) are forming a pair of Hilbert transforms.
Sukkar et al. defined the function zinc (t) = A sinc (t) + B cosc (t). It is pointed out that the terms sinc (t) and cosc (t) are forming a pair of Hilbert transforms.
In recent years, there have been a number of studies addressing both reversible and irreversible compression of medical images ranging from 256 x 256 to 2048 x 2048 pixels in spatial resolution. There is a need to add...
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In recent years, there have been a number of studies addressing both reversible and irreversible compression of medical images ranging from 256 x 256 to 2048 x 2048 pixels in spatial resolution. There is a need to address the high-resolution end of the image categories, namely mammograms and chest X-rays, which require resolution of the order of 4096 x 4096 pixels. Further, data compression schemes for most medical applications have to be information-preserving or reversible. In this paper, the performance of a number of block-based, reversible, compression algorithms suitable for compression of very large-format images (4096 x 4096 pixels or more) is compared to that of a novel two-dimensional linearpredictive coder developed by extending the multichannel version of the Burg algorithm to two dimensions. The compression schemes implemented are: Huffman coding, Lempel-Ziv coding, arithmetic coding, two-dimensional linear predictive coding (in addition to the aforementioned one), transform coding using discrete Fourier-, discrete cosine-, and discrete Walsh transforms, linear interpolative coding, and combinations thereof. We discuss the performance of these coding techniques with a few mammograms and chest radiographs digitized to sizes up to 4096 x 4096, 10 b pixels. We have achieved compression from 10 bits to 2.5-3.0 b/pixel on these images without any loss of information. The modified multichannel linear predictor out-performs the other methods while offering certain advantages in implementation.
The 'devils's staircase' succession of subharmonic and chaotic orbits observed in a second-order driven oscillator by L. Chua, Y. Yao, and Q. Yang is reproduced and extended by numerical simulation. More h...
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The 'devils's staircase' succession of subharmonic and chaotic orbits observed in a second-order driven oscillator by L. Chua, Y. Yao, and Q. Yang is reproduced and extended by numerical simulation. More hierarchical levels have been obtained and a more detailed law for the sequences of subharmonics and their locking frequencies is conjectured.< >
An efficient method to implement the perceptual posterfilter for the suppression of coding noise in CELP-coded speech is proposed. The method is based on approximating the response of an all-pole filter to the respons...
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An efficient method to implement the perceptual posterfilter for the suppression of coding noise in CELP-coded speech is proposed. The method is based on approximating the response of an all-pole filter to the response of the pole-zero form postfilter via cepstrum processing. This all-pole postfilter can then be implemented more efficiently than the pole-zero postfilter with less computation and filter memory.
The authors show that for small errors in an LPC model, spectral distortion and weighted squared distortion measures in the coefficients of arbitrary one-to-one transformations of the LPC parameters are equivalent. Fo...
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The authors show that for small errors in an LPC model, spectral distortion and weighted squared distortion measures in the coefficients of arbitrary one-to-one transformations of the LPC parameters are equivalent. For line spectrum pairs and immitance spectrum pairs, the weighting matrix is diagonal, which is advantageous for efficient quantisation.
A novel scheme of generating the codebook for vector quantisation is presented. With the initial codebook resulting from a K-d tree splitting procedure based on the greatest coordinate variance, a proposed partial GLA...
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A novel scheme of generating the codebook for vector quantisation is presented. With the initial codebook resulting from a K-d tree splitting procedure based on the greatest coordinate variance, a proposed partial GLA is used to improve the codevectors. The performance of the VQ so obtained is superior to those of the VQ designed by the standard GLA with the same initialisation and the splitting-initialised LEG algorithm. However, the improvement in performance is accompanied by an increase in the computational complexity involved in the designed stage.
It is shown that a positive definite symmetric Toeplitz matrix of rank p+1 can be represented uniquely by the minimum eigenvalues of itself and its p submatrices, along with a sign bit for each eigenvalue. The applica...
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It is shown that a positive definite symmetric Toeplitz matrix of rank p+1 can be represented uniquely by the minimum eigenvalues of itself and its p submatrices, along with a sign bit for each eigenvalue. The application of such a procedure allows specification of linear prediction coding (LPC) spectra by an alternate set of parameters. It also enables extension of an autocorrelation sequence using a nonstandard criterion. A number of parallels are made between these parameters and the LPC mean-square error values for successively higher-order systems. An application involving maximum entropy spectral estimation under a nonstandard set of constraints is presented.< >
A new form of line spectral frequency (FSF), bounded line spectral frequency, is presented. It is shown that the new representation is more efficient than the direct line spectral frequency and the differential line s...
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A new form of line spectral frequency (FSF), bounded line spectral frequency, is presented. It is shown that the new representation is more efficient than the direct line spectral frequency and the differential line spectral frequency (DLSF). By using a vector measure, the scalar quantisation of tenth-order linear predictive coding (LPC) parameters can be coded at 28 bit/frame with a transparent quantisation quality.
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