The objective behind transformcoding is to transform a data array into a statistically uncorrelated set. The uneven distribution of energy in transform coefficients is exploited for compression purposes, with signifi...
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(纸本)0819423173
The objective behind transformcoding is to transform a data array into a statistically uncorrelated set. The uneven distribution of energy in transform coefficients is exploited for compression purposes, with significant energies considered for further processing. Block transforms, particularly the discrete cosine transform, have been used in image-video coding. An approximate Fourier expansion (AFE) of non-periodic signals with theoretically uncorrelated coefficients has been previously proposed. Furthermore, the capabilities of an approximate cosine expansion (ACE) have been explored for purposes of image coding. In this paper, we apply an approximate trigonometric expansion to images and investigate the potential of adaptivecoding using blocks of images. The variable length basis functions computed by varying a user-defined parameter of the expansion will be used for adaptive transform coding of images. For comparison purposes, the results will be compared with discrete cosine transform (DCT). Computer simulation results will also be presented.
adaptive transform coding incorporating Time Domain Aliasing Cancellation (TDAC) is presented in this paper for speech coding at low data rates. The TDAC transform differs from the conventional Discrete Cosine Transfo...
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adaptive transform coding incorporating Time Domain Aliasing Cancellation (TDAC) is presented in this paper for speech coding at low data rates. The TDAC transform differs from the conventional Discrete Cosine transform (DCT) in that the analysis/synthesis window length can be longer than the system decimation factor. The channel bandwidth of the TDAC transform is narrower when compared to the DCT and therefore results in less spectral interaction occurring between bands. The TDAC transform coder employs forward adaptive scalar quantization of the transform coefficients and dynamic bit allocation over a block time corresponding to three transform operations. The associated side information is vector quantized, resulting in a side information overhead of 1.625 K bits per second. Both subjective and objective comparisons were made between TDAC and DCT coders at data rates of 9.6 K, 12 K and 16 K bits per second. The objective comparison involved segmental signal to noise ratio (SNRSEG) measurements while the subjective quality assessment was determined from A-B comparisons of recovered speech passed through the TDAC coder, the DCT coder and log PCM coders. The results indicate the TDAC transform coder is both objectively and subjectively superior to a transform coder employing the conventional DCT. Dieser Beitrag beschäftigt sich mit adaptiver transformationscodierung von Sprachsignalen bei niedrigen Datenraten unter Verwendung des Verfahrens der Kompensation von Aliasverzerrungen im Zeitbereich (Time Domain Aliasing Cancellation, TDAC). Die TDAC transformation unterscheidet sich von der üblicherweise verwendeten diskreten Kosinustransformation (Discrete Cosine transform, DCT) dadurch, daβ die Länge des für die Analyse und Synthese verwendeten Fensters gröβer sein kann als durch den Reduktionsfaktor des Systems vorgegeben. Die benötigte Bandbreite ist bei der TDAC transformation kleiner als bei der DCT; hierdurch verringert sich die gegenseitige Beeinflussung benachba
transform plays a crucial role in video coding, since it is in the transform domain that the bitrate reduction happens. Recently, coding with transform competition has emerged, especially inside the ITU-T and ISO/ MPE...
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transform plays a crucial role in video coding, since it is in the transform domain that the bitrate reduction happens. Recently, coding with transform competition has emerged, especially inside the ITU-T and ISO/ MPEG Joint Video Exploration Team, where the adaptive multiple transforms have been thoroughly tested. In this paper, it is proposed to investigate the design of transform competition systems for the purpose of inter-predicted residuals. Several systems are proposed and evaluated in terms of coding efficiency, storage requirement, and encoding complexity. A first approach selects the best transform for a residual block in a pre-established list of transforms. An extended version is also considered, where the number of transforms varies within an image area. Experimental results show that the proposed designs achieve significant bitrate savings over high efficiency video coding from -0.2% to -1.4%.
A new synthetic high coding is presented for high data compression. In this scheme, only the lowpass image is transmitted, which is composed of the low-frequency components of an image, through subsampling and adaptiv...
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A new synthetic high coding is presented for high data compression. In this scheme, only the lowpass image is transmitted, which is composed of the low-frequency components of an image, through subsampling and adaptive transform coding (ATC). Then it is expanded by interpolation at the receiver. The highpass image is simply synthesised without any overhead information by edge-sharpening the expanded lowpass image. The result of the proposed scheme shows acceptable image quality even at a high compression ratio of about 30:1
In this paper, we establish a probabilistic framework for adaptive transform coding that leads to a generalized Lloyd type algorithm for transform coder design. transform coders are often constructed by concatenating ...
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In this paper, we establish a probabilistic framework for adaptive transform coding that leads to a generalized Lloyd type algorithm for transform coder design. transform coders are often constructed by concatenating an ad hoc choice of transform with suboptimal bit allocation and quantizer design. Instead, we start from a probabilistic latent variable model in the form of a mixture of constrained Gaussian mixtures. From this model, we derive an transform coder design algorithm, which integrates optimization of all transform coder parameters. An essential part this algorithm is our introduction of a new transform basis-the coding optimal transform-which, unlike commonly used transforms, minimizes compression distortion. adaptivetransform coders can be effective for compressing databases of related imagery since the high overhead associated with these coders can be amortized over the entire database. For this work, we performed compression experiments on a database of synthetic aperture radar images. Our results show that adaptive coders improve compressed signal-to-noise ratio (SNR) by approximately 0.5 dB compared with global coders. Coders that incorporated the coding optimal transform had the best SNRs on the images used to develop the coder. However, coders that incorporated the discrete cosine transform generalized better to new images.
In DCT coding of an image, the image is divided into square blocks, and variable-separation two-dimensional DCT is applied, with one-dimensional DCTs applied to the rows and columns in cascade. In the variable-separat...
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In DCT coding of an image, the image is divided into square blocks, and variable-separation two-dimensional DCT is applied, with one-dimensional DCTs applied to the rows and columns in cascade. In the variable-separation transform, the power packing efficiency is low at the edge in the slant direction of the image. Another problem is that mosquito noise may be produced near the edge in the restored image, which degrades the image quality. This article proposes adaptive DCT coding in which the two-dimensional DCT on the skew coordinates and variable shape region segmentation according to the direction of the edges are introduced. In the proposed method, the shape of the region is restricted to rhombic, triangular, and rectangular blocks to simplify the segmentation and transform processes. The DCT for triangular block is a nonorthogonal two-dimensional DCT in which the normalization factor is determined so that the DC base is used as the transform base, This helps to improve performance in the flat part of the image. The power packing efficiency is estimated, and it is shown that the DCT in skew coordinates can improve the power packing efficiency compared to the conventional square block DCT, and achieves results comparable to the direction-adaptive Karhunen-Loeve transform. The result of a simulation experiment is shown, which shows that the proposed method is useful in reducing mosquito noise. (C) 1999 Scripta Technica.
Advances in signal processing allow us to model the audio signal in terms of mathematical representation. Compressed audio signal are also important for low-bit-rate media in order to minimize transmission cost. Appli...
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Advances in signal processing allow us to model the audio signal in terms of mathematical representation. Compressed audio signal are also important for low-bit-rate media in order to minimize transmission cost. Applications such as movies on compact disc, audio conferencing, and digital television also require a good model for the audio compression. We present a model for compressed audio signal. By varying different modelling parameters, we obtain the simulation result of the proposed model of the audio coder. Simulation results found that it has a good compression Ssignal-to-noise ratio compared with NICAM, CD, and OCF coders.
In DCT coding of an image, the image is divided into square blocks, and variable-separation two-dimensional DCT is applied, with one-dimensional DCTs applied to the rows and columns in cascade. In the variable-separat...
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