共查询到19条相似文献,搜索用时 178 毫秒
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本文对一维DCT变换压缩编码中变换域系数二次量化引起的图象损伤进行了频域和空间域分析,得出了一些有用的结论.通过对变换矩阵系数字长的分析和计算机模拟,为一维DCT变换压缩编码硬件实现时字长的确定提供了依据.硬件实验结果印证了上述分析的结论. 相似文献
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深入分析了预测编码与DCT变换编码的异同点,并从编码增益、块效应系数、预测与变换与变换前后的能量关系等多方面比较了两种编码的优缺点。 相似文献
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对H.264协议的变换编码和量化进行了理论分析,给出了具体实现过程,论证了这种变换和量化方式的特点、有效性及应用前景。 相似文献
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数字音频压缩中的变换编码算法 总被引:11,自引:3,他引:8
变换编码是音频压缩中的一个重要部分,文中叙述MPEG音频编码标准中的变换编码技术,包括改进余弦变换和反变换(MDCT和IMDCT)时域混叠抵消与自适应窗选择,详细推导了MDCT和IMDCT的快速算法。 相似文献
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本文介绍了一种建立在心理声学基础上的适用于宽频带数字音频信号的数据压缩技术,我们利用计算机对自适应变换编解码法的全过程进行了模拟,并采用Motorola公司的数字信号处理芯片DSP56009作为硬件平台,实现了高质量的音频信号压缩编码,试验结果压缩比达到1/10以下,而且没有明显的音质衰减。 相似文献
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The 2D-discrete cosine transform (2D-DCT) is one of the popular transformation for video coding. Yet, 2D-DCT may not be able to efficiently represent video data with fewer coefficients for oblique featured blocks. To further improve the compression gain for such oblique featured video data, this paper presents a directional transform framework based on direction-adaptive fixed length discrete cosine transform (DAFL-DCT) for intra-, and inter-frame. The proposed framework selects the best suitable transform mode from eight proposed directional transform modes for each block, and modified zigzag scanning pattern rearranges these transformed coefficients into a 1D-array, suitable for entropy encoding. The proposed scheme is analysed on JM 18.6 of H.264/AVC platform. Performance comparisons have been made with respect to rate-distortion (RD), Bjontegaard metrics, encoding time etc. The proposed transform scheme outperforms the conventional 2D-DCT and other state-of-art techniques in terms of compression gain and subjective quality. 相似文献
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Hadamard transform image coding 总被引:1,自引:0,他引:1
The introduction of the fast Fourier transform algorithm has led to the development of the Fourier transform image coding technique whereby the two-dimensional Fourier transform of an image is transmitted over a channel rather than the image itself. This devlopement has further led to a related image coding technique in which an image is transformed by a Hadamard matrix operator. The Hadamard matrix is a square array of plus and minus ones whose rows and columns are orthogonal to one another. A high-speed computational algorithm, similar to the fast Fourier transform algorithm, which performs the Hadamard transformation has been developed. Since only real number additions and subtractions are required with the Hadamard transform, an order of magnitude speed advantage is possible compared to the complex number Fourier transform. Transmitting the Hadamard transform of an image rather than the spatial representation of the image provides a potential toleration to channel errors and the possibility of reduced bandwidth transmission. 相似文献
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After the successful development of the discrete cosine transform (DCT) especially in audio, image and video coding, many state-of-the-arts DCT-based fast algorithms have been developed. However, these algorithms are floating-point and are implemented with high algorithmic complexity and memory intensive. Therefore, they consume large system resources. In particular, those requirements pose a serious limitation on multimedia applications in resource-constrained systems, such as wireless multimedia sensor networks (WMSNs). In this paper we investigate an alternative to DCT transform which known as discrete Tchebichef transform (DTT). Despite its good energy compaction property, low algorithmic complexity and low memory requirements, the DTT is potentially unexploited in the literature. To further reduce its complexity and memory requirements, in this paper we propose a pruned version of DTT (P-DTT). Simulation results show that P-DTT requires a reduced number of arithmetic operations, energy consumption and memory. And it has at the same time competitive compression efficiency compared with Loeffler-DCT and exact DTT. The proposed P-DTT transform is a viable option for image compression and/or communication over WMSNs. 相似文献
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Effros M. Hanying Feng Zeger K. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2004,50(8):1605-1619
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. 相似文献
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In this paper, an adaptive three-dimensional transform coding technique based on the 3-D discrete cosine transform (DCT) for removing the temporal correlation is proposed. Because of the nonstationary nature of the image data, the energy distribution in a 3-D DCT block varies along the vertical, horizontal and temporal directions. Thus, adaptive schemes, such as the 3-D classification, the classified linear scanning technique and the VLC table selection scheme, are used to take local variations into account. Also, in our approach, a hybrid technique, which adaptively combines relatively simple inter-frame coding with intra-frame coding, is presented. Through intensive computer simulations, the performance of the proposed 3-D transform coding technique is evaluated on several well-known moving sequences. The results show that, especially for moving sequences containing slow or moderate motion, the proposed technique provides an improved performance over the scheme with motion compensation (CCITT, 1989) at rates above 0.5 b/pixel (bpp), and a good visual quality of the reconstructed images is also obtained. Thus, the proposed 3-D transform coding technique is believed to be a good candidate for the digital VCR, since motion compensation is not required in the proposed 3-D coding technique. 相似文献
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Diaa M. El Rayess S. Ghoniemy S. F. Bahgat 《Circuits, Systems, and Signal Processing》1994,13(1):3-18
Image coding can be implemented through DPCM, transform, hybrid, or segmentation coding techniques. Some transform coding techniques, such as cosine and Hadamard, have been exhaustively analyzed and evaluated, while others, such as Legendre, have not. This paper introduces the use of Legendre transform in image coding. The transform matrix for different block sizes is calculated, the fast algorithm is derived, and the performance is evaluated through both mean square error and subjective quality. The results obtained have indicated that the system performance is comparable with that of optimum KLT and cosine transforms; moreover, it is simpler in implementation. 相似文献
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小波变换在傅立叶变换轮廓术中的应用 总被引:1,自引:0,他引:1
从小波变换本质、原理出发 ,说明它在提取条纹位相方面的应用 ,通过阐述小波变换与傅立叶变换两者之间的内在联系 ,将小波变换应用到傅立叶变换轮廓术中 ,并着重用傅立叶变换的原理对小波提取位相的原理进行详细解释。模拟结果表明 :小波变换在傅立叶变换轮廓术中的应用是正确的、可行的。 相似文献