Adaptive predictive coding (APC) is a useful technique for high-quality digital encoding of speech signals at medium band data rates. A particularly annoying degradation in APC systems, however, is the presence of &qu...
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Adaptive predictive coding (APC) is a useful technique for high-quality digital encoding of speech signals at medium band data rates. A particularly annoying degradation in APC systems, however, is the presence of "glitches" or "beeps" in the output speech. These correspond to frames with signal-to-quantization-noise ratios (S/Q) that are often less than unity, i.e., negative in dB. We show that these degradations are caused by instabilities of the APC system. This paper provides a method for analyzing the stability of APC systems as a function of the encoding bit rate, the quantization algorithm, and the power gain of the APC loop feedback filter. Two methods of improving system performance based on the results of the stability analysis are then developed. Experimental evaluation by listening tests confirm the validity of the techniques.
Studies parallel processing algorithms of linear prediction of speech parameters. The autoregressive speech vector series with stable covariance, can be gained after a classification of adjacent samples of source spee...
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Studies parallel processing algorithms of linear prediction of speech parameters. The autoregressive speech vector series with stable covariance, can be gained after a classification of adjacent samples of source speech series. A strategy of vector predictive coding with highly parallel processing ability can be achieved with the application of the principle of orthogonal projection in Hilbert space. Finally it is confirmed that the algorithms are effective by computer simulation.
In this paper, we propose a simple search order entropy coding algorithm to compress grey level scale images on lossless basis. We also describe a CAM (content addressable memory) based architecture design for real-ti...
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In this paper, we propose a simple search order entropy coding algorithm to compress grey level scale images on lossless basis. We also describe a CAM (content addressable memory) based architecture design for real-time implementation of the proposed algorithm. Extensive experiments carried out prove that the work presented provides not only a competitive alternative in comparison with JPEG lossless compression mode but also a practical solution to lossless image compression.
In this paper, we present three novel lossless compression approaches for gray-scale continuous tone natural image. Our methods enhance the median edge detector (MED), which is the core part of JPED-LS algorithm, by r...
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In this paper, we present three novel lossless compression approaches for gray-scale continuous tone natural image. Our methods enhance the median edge detector (MED), which is the core part of JPED-LS algorithm, by reducing the entropy of the prediction error via adaptive regression. These modified predictors improve the prediction accuracy by reducing the negative effect due to MED's oversimplified edge orientation detection. The experimental results show that our approaches achieve evidently better performance than MED with only neglectable increasing of computational complexity and without introduce extra pixels into the causal template
A novel predictive coding scheme is presented where the residual correlations between VQ contiguous blocks are exploited by a neural predictor. A further compression is then achieved via a dynamic codebook reordering ...
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A novel predictive coding scheme is presented where the residual correlations between VQ contiguous blocks are exploited by a neural predictor. A further compression is then achieved via a dynamic codebook reordering and a more efficient Huffman encoding of vector addresses.< >
In this paper we present a new method for image coding that is able to achieve good results over a wide range of image types. This work is based on the multidimensional multiscale parser (MMP) algorithm (M. de Carvalh...
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In this paper we present a new method for image coding that is able to achieve good results over a wide range of image types. This work is based on the multidimensional multiscale parser (MMP) algorithm (M. de Carvalho et al., 2002), allied with an intra frame image predictive coding scheme. MMP has been shown to have, for a large class of image data, including texts, graphics, mixed images and textures, a compression efficiency comparable (and, in several cases, well above) to the one of state-of-the-art encoders. However, for smooth grayscale images, its performance lags behind the one of wavelet-based encoders, as JPEG2000. In this paper we propose a novel encoder using MMP with intra predictive coding, similar to the one used in the H.264/AVC video coding standard. Experimental results show that this method closes the performance gap to JPEG-2000 for smooth images, with PSNR gains of up to 1.5 dB. Yet, it maintains the excellent performance level of the MMP for other types of image data, as text, graphics and compound images, lending it a useful universal character.
Enhanced intra and inter prediction techniques are the key factors to the success of H.264. There are a total of nine optional prediction modes for each 4 times 4 luma block. The choice of intra prediction mode for ea...
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Enhanced intra and inter prediction techniques are the key factors to the success of H.264. There are a total of nine optional prediction modes for each 4 times 4 luma block. The choice of intra prediction mode for each 4 times 4 block must be signalled to the decoder and this could potentially require a large number of bits. However, intra modes for neighbouring 4 times 4 blocks are often correlated. To take advantage of this correlation, predictive coding is used to signal 4 times 4 intra modes. At the boundaries of frame, we can't apply all modes because of limitation of available pixels for prediction. Now question arises, is it feasible to use same technique to signal less number of modes as for nine modes? In this paper we used techniques different than the given technique for nine modes, experimental results show that the proposed methods are more efficient than the existing one
A suboptimal searching procedure of innovation sequence for code excited linear predictive (CELP) coding algorithms is described. A three-step search algorithm has been investigated. The first step consists of a MPLPC...
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A suboptimal searching procedure of innovation sequence for code excited linear predictive (CELP) coding algorithms is described. A three-step search algorithm has been investigated. The first step consists of a MPLPC (multipulse linear predictive coding) algorithm. From a codebook containing 1024 Gaussian central-clipped sequences a reduced set of about 40 innovation sequences is selected using the multipulse sequence computed in the first step. The final innovation sequence is determined by performing the full search algorithm with the reduced set of sequences. Informal subjective listening tests were made with speech coded using the three-step algorithm.< >
Compression efficiency and bitrate scalability are among the key factors in video coding. The paper introduces novel sub-sequence coding techniques for temporal scalability. The presented coding schemes provide a wide...
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Compression efficiency and bitrate scalability are among the key factors in video coding. The paper introduces novel sub-sequence coding techniques for temporal scalability. The presented coding schemes provide a wider range for bitrate scaling than conventional temporal scalability methods and maintain high coding efficiency at the same time. The proposed sub-sequence techniques are adopted into the latest video coding standard, H.264, making it easy to identify sub-sequences and possible to discard them intentionally. As shown by extensive simulations, a wide range of applications, from mobile messaging to consumer electronics, such as digital TV, can benefit from sub-sequences.
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