Motion-compensated interframe transform coding has been recommended as an efficient method of coding image sequences at low bit rates. The paper considers the effect of employing a variety of different transform and m...
详细信息
Motion-compensated interframe transform coding has been recommended as an efficient method of coding image sequences at low bit rates. The paper considers the effect of employing a variety of different transform and motion compensation techniques on the operation of the algorithm and also the interrelation between the predictive and transform parts of the scheme in terms of the spectral properties of the signal to be transformed. It is shown that, for a wide variety of source material, there is a complex interaction between the specific transform and motion compensation scheme employed, and that the efficiency of the motion-compensated predictive operation strongly influences the performance of the subsequent transform step.
We examine the performance of the Karhunen-Loeve transform (KLT) for transform coding applications. The KLT has long been viewed as the best available block transform for a system that orthogonally transforms a vector...
详细信息
We examine the performance of the Karhunen-Loeve transform (KLT) for transform coding applications. The KLT has long been viewed as the best available block transform for a system that orthogonally transforms a vector source, scalar quantizes the components of the transformed vector using optimal bit allocation, and then inverse transforms the vector. This paper treats fixed-rate and variable-rate transform codes of non-Gaussian sources. The fixed-rate approach uses an optimal fixed-rate scalar quantizer to describe the transform coefficients;the variable-rate approach uses a uniform scalar quantizer followed by an optimal entropy code, and each quantized component is encoded separately. Earlier work shows that for the variable-rate case there exist sources on which the KLT is not unique and the optimal quantization and coding stage matched to a "worst" KLT yields performance as much as 1.5 dB worse than the optimal quantization and coding stage matched to a "best" KLT. In this paper, we strengthen that result to show that in both the fixed-rate and the variable-rate coding frameworks there exist sources for which the performance penalty for using a "worst" KLT can be made arbitrarily large. Further, we demonstrate in both frameworks that there exist sources for which even a best KLT gives suboptimal performance. Finally, we show that even for vector sources where the KLT yields independent coefficients, the KLT can be suboptimal for fixed-rate coding.
In this paper, the correlation properties are used to develop two efficient encoding schemes for speech line spectrum frequency (LSF) parameters. The first scheme (1D KL), which exploits the intraframe correlation, is...
详细信息
In this paper, the correlation properties are used to develop two efficient encoding schemes for speech line spectrum frequency (LSF) parameters. The first scheme (1D KL), which exploits the intraframe correlation, is based on one-dimensional Karhunen-Loeve (KL) transformation;the second scheme, which requires some coding delays to further utilize the interframe correlation, uses two-dimensional (2D KL) transform in the frequency domain or one-dimensional KL transform co-operating with DPCM in the time domain. Moreover, since the KL transform is globally optimal, which is sensitive to the change of input data statistics, further two adaptive transform coding systems are also investigated in this paper. The performance of all systems for different bit rates is investigated and adequate comparisons are made. It is shown that the gain of using KL transformation to exploit the intraframe and interframe correlation is 3 and 3 bits/speech frame, respectively.
The development of real-time 3D sensing devices and algorithms (e.g., multiview capturing systems, Time-of-Flight depth cameras, LIDAR sensors), as well as the widespreading of enhanced user applications processing 3D...
详细信息
The development of real-time 3D sensing devices and algorithms (e.g., multiview capturing systems, Time-of-Flight depth cameras, LIDAR sensors), as well as the widespreading of enhanced user applications processing 3D data, have motivated the investigation of innovative and effective coding strategies for 3D point clouds. Several compression algorithms, as well as some standardization efforts, has been proposed in order to achieve high compression ratios and flexibility at a reasonable computational cost. This paper presents a transform-based coding strategy for dynamic point clouds that combines a non-linear transform for geometric data with a linear transform for color data;both operations are region-adaptive in order to fit the characteristics of the input 3D data. Temporal redundancy is exploited both in the adaptation of the designed transform and in predicting the attributes at the current instant from the previous ones. Experimental results showed that the proposed solution obtained a significant bit rate reduction in lossless geometry coding and an improved rate-distortion performance in the lossy coding of color components with respect to state-of-the-art strategies.
A technique for generating independent transform coefficients from any p-dependent signal has been developed. Since these coefficients are independent, the Lloyd-Max quantization efficiency is improved. In addition, t...
详细信息
A technique for generating independent transform coefficients from any p-dependent signal has been developed. Since these coefficients are independent, the Lloyd-Max quantization efficiency is improved. In addition, these coefficients are shown to be Gaussian distributed. Therefore, the probability density function estimate is bypassed during the quantizer design. An all-pass (encryption) pre-filter is required by the proposed technique, and the filtered signal is obtained efficiently by an algorithm developed in this paper. An added benefit of this technique is the compatibility and higher security with respect to the conventional transform coding (TC), and the method is called the transform encryption coding (TEC), In addition, a post-filter is necessary for signal reconstruction Due to the all-pass nature of the pre/post-filtering process, the mean-square quantization error for the complete process is equal to that for the intermediate independent Gaussian transform coefficients. Simulation results show TEC achieves about 1 dB coding gain compared with TC. Coded images without blocking effects are obtained at 0.5 bit/pixel (bpp) using TEC. The image quality is similar to that obtained by TC at 1 bpp. Even at 0.35 bpp, TEC performs in the same way as the recent 'DCT/DST' technique of Rose et al. (1990) and shows no blocking effects. Most significantly, TEC encoded image is insensitive and robust to the channel noise.
In this letter, we provide a theoretical analysis of optimal predictive transform coding based on the Gaussian Markov random field (GMRF) model. It is shown that the eigen-analysis of the precision matrix of the GMRF ...
详细信息
In this letter, we provide a theoretical analysis of optimal predictive transform coding based on the Gaussian Markov random field (GMRF) model. It is shown that the eigen-analysis of the precision matrix of the GMRF model is optimal in decorrelating the signal. The resulting graph transform degenerates to the well-known 2-D discrete cosine transform (DCT) for a particular 2-D first order GMRF, although it is not a unique optimal solution. Furthermore, we present an optimal scheme to perform predictive transform coding based on conditional probabilities of a GMRF model. Such an analysis can be applied to both motion prediction and intra-frame predictive coding, and may lead to improvements in coding efficiency in the future.
The distributed Luby transform (LT) coding is investigated for the multisource networks, especially with three sources. Based on the three-source single-relay network model, the authors propose a threefold deconvoluti...
详细信息
The distributed Luby transform (LT) coding is investigated for the multisource networks, especially with three sources. Based on the three-source single-relay network model, the authors propose a threefold deconvolution method of the robust soliton distribution (RSD). The deconvolved distribution is used at each source, and a simple and feasible combining algorithm is developed for re-encoding at the relay. Such a modified LT code with three sources (MLT-3) is constructed. Simulation results verify that the overall degree distribution of the proposed MLT-3 codes agrees well with the RSD. The performance of MLT-3 codes is evaluated and compared with other coding schemes. Simulations reveal that MLT-3 codes have similar behaviour with the two-source or four-source distributed LT codes and the benefits are observed in comparison with the separate LT codes. Simulations also show that MLT-3 codes exhibit good performance on various erasure channels.
transform coding has been successfully used for image compression in many applications. However, it suffers from the artifact known as ''blocking effect'' due to division of subblocks. In this paper, w...
详细信息
transform coding has been successfully used for image compression in many applications. However, it suffers from the artifact known as ''blocking effect'' due to division of subblocks. In this paper, we propose a combined-transform coding (CTC) scheme to reduce this effect and hence achieve better subjective performance. First the proposed CTC scheme was described and its information-theoretic properties were investigated. Then a comparison between the CTC scheme and the DCT-based JPEG system and DWHT scheme was made to demonstrate the performance improvement of the proposed scheme. The advantages of the proposed CTC scheme also include 1): no ringing effect due to no error propagation across the boundary, 2): no additional computation and 3): distortion can be held below a certain threshold.
An alternative transform coder design criterion based on restricting the maximum perceptual error of each coefficient is proposed. This perceptually uniform quantisation of the transform domain ensures that the percep...
详细信息
An alternative transform coder design criterion based on restricting the maximum perceptual error of each coefficient is proposed. This perceptually uniform quantisation of the transform domain ensures that the perceptual error will be below a certain limit regardless of the particular input image. The results show that the proposed criterion improves the subjective quality of the conventional average error criterion even if it is weighted with the same perceptual metric.
Traditionally, any 2-D transform (such as 2-D DCT) is implemented through two separable 1-D transforms along the vertical and horizontal dimensions. Such a framework is however not most suitable for a 2-D directional ...
详细信息
Traditionally, any 2-D transform (such as 2-D DCT) is implemented through two separable 1-D transforms along the vertical and horizontal dimensions. Such a framework is however not most suitable for a 2-D directional source in which the dominant directional information is neither horizontal nor vertical. In this letter, we attempt to determine the R-D performance upper bound for block-based transform coding schemes applied on such 2-D directional sources. It is not a surprise that the Karhunen-Loeve transform (KLT) plays a critical role here. Specifically, we show that a nonseparable KLT can be determined directly from the given 2-D directional source model to yield the R-D performance upper bound. We also show that there exists a significant gap between this upper bound and the R-D performance that can be achieved by using the traditional 2-D DCT.
暂无评论