双正交DCT在视频编码中的实现

采用仅有移位和加法操作的提升步长的双正交DCT变换来实现H.263视频压缩编码中的DCT变换。双正交DCT能快速有效地实现整数到整数的变换,在C6201定点DSP中,双正交DCT的编码速度与DCT相比有很大提高。     

H．264整数DCT的FPGA实现

H.264整数DCT变换算法有助于减少计算复杂度,提高编码速度,进一步提高视频或图像的压缩效率。分析H.264整数DCT变换的快速算法及其实现原理,并提出一种用来具体实现一个4×4块的DCT变换的结构;同时给出用VHDL语言实现4×4块DCT变换的内部模块的源代码和仿真波形。仿真结果表明用该算法可快速实现一个4×4块的整数DCT变换。提出一种切实可行的用于H.264整数DCT变换的结构,该结构可完全用硬件电路快速实现;对于用FPGA实现H.264整数DCT变换做了一次实践性的尝试,对深入理解H.264整数DCT变换及其算法的具体实现具有一定的实践意义。     

双正交重叠变换的整数实现算法与图像压缩

本文利用提升原理,以二进制整数DCT为基础,提出了双正交重叠变换的整数实现算法,其计算只需要少量的移位和加法运算,因而软件实现和硬件实现都非常简单.实验结果表明,它是一种有效的图像压缩变换,压缩质量大大超过了运算量更多的近似二进制整数小波变换和DCT,与Daubechies 9/7小波也非常接近.     

AVS变换域降分辨率快速算法

研究了AVS变换域降分辨率算法,给出一个与8点整数DCT变换相对应的4点整数DCT变换核,并据此导出变换域降分辨率的快速算法.实验仿真表明,算法与时域线性内插降采样相比能够显著降低运算复杂度,视频效果也表现良好.     

基于ADSP—BF533的H．264DCT变换及量化的优化实现

根据ITU-T提出的H.264视频编解码标准,对JM算法及TI Blackfin 533 DSP自身特点进行了分析,将标准中编码采用的整数离散余弦变换(DCT)、量化,解码采用的反DCT变换、反量化的JM算法成功移植到DSP上面,同时根据DSP的特点进行软硬件优化,达到了较好效果。     

H.264/AVC中变换量化模块的可重构设计

基于H.264/AVC视频编码标准,完成编码模块中的整数OCT/Q模块可重构IP核的优化设计.在硬件开销改变不大的情况下,利用可重构理论,提炼出其核心部件即可重构处理元,在同种电路结构上实现变换量比(DCT/Q)和反变换反量比(IDCT/IQ)的功能,满足高清视频实时编解码要求.     

H．264／AVC中的整数变换与DCT变换的比较

数字视频技术在通信和广播领域获得了日益广泛的应用,视频信息和多媒体信息在网络中的处理和传输成为当前我国信息化中的热点技术。运动图像专家组和视频编码专家组给出一种更好的标准,确定为MPEG-4标准的第十部分,即H.264/AVC。简述H.264的研究意义及DCT的原理。为了减少运算量,分析H.264中如何对宏块的整数变换,详述H.264的编码变换的方法,给出整数变换方法与传统的DCT的区别和联系,并给出H.264的整数变换方法的快速算法即蝶形算法,这与传统的DCT变换是不同的。     

H.264视频编码器在DM6437上的优化实现

为了实现基于DSP的H.264视频编码器的实时性能,提出了一系列优化实现方法。首先结合TMS320DM6437硬件特点,描述了X264代码向TMS320DM6437平台的移植过程和优化方法,重点介绍了整数DCT变换和量化的线性汇编编写及汇编级优化。实验结果表明,本编码器实现了cif格式视频的实时编码,Dl格式视频的编码速率也达到了18 fps,基本满足视频监控系统中编码器的需求。     

一种高性能的H.264变换编码IP设计

H.264是ITU与ISO联合共同开发的具有高编码效率、高压缩质量的视频新标准.H.264采用了4×4 块的无乘法整数变换编码算法,有效地降低了编解码的运算量,且避免了反变换的误匹配问题.文章通过详细分析H.264的整数DCT变换及Hardmard变换的算法,提出了一种高性能的变换编码的硬件IP设计,通过Modlesim仿真和DC综合能较好地达到预先设计要求.     

一种基于DSP的块等级预判DCT算法

本文提出一种基于块等级预判的DCT算法,并讨论了该算法的块等级预判准则以及在DSP上实现了DCT的快速实现方法,该方法在基于DSP的视频编码中取得了良好效果。     

Low complexity shape-adaptive DCT for coding of arbitrarily shaped image segments

A low complexity shape-adaptive DCT transform algorithm for coding pels in arbitrarily shaped image segments is presented. The proposed algorithm is compared to the well established generalized shape-adaptive transform method introduced by Gilge et al. in terms of transform efficiency and computational complexity. Results obtained under both theoretical and experimental conditions show that the new algorithm achieves a transform efficiency close to that of the Gilge method with considerably reduced computational complexity. The proposed shape-adaptive DCT algorithm was implemented into a standard MPEG-1 coder to provide object or segment based coding of images and video with additional content-based functionality. The extended MPEG-1 object based coding scheme can handle generic input sequences and can readily provide MPEG-1 backward compatibility if no contour data is transmitted for a given video sequence. Results for INTRA coding of images indicate that the algorithm allows efficient coding over a wide range of coding parameters — thus providing means for generic coding of segmented video between very high and very low bit rates. It is further shown that some of the content-based based functionalities currently discussed in MPEG-4 can be provided efficiently using the proposed object based coding scheme.     

A pixel-wise directional intra prediction method

In a decade where the prominence of video applications has become increasingly prevalent, the optimization of video coding processes remains as important as ever. The directional intra prediction has been proved as an effective tool for intra picture coding. However, in a directional intra prediction based coding structure, there is a considerable gap between the transform efficiency of DCT and the optimal transform KLT. In this paper, we analyze these problems and propose a pixel-wise directional intra prediction (PDIP) method to solve this problem. This method exploits the reconstruction value of the adjacent pixels to predict the current pixel, and keeps the block-based lossy coding structure of H.264/AVC. The proposed method can significantly improve the coding efficiency with little decoding complexity increment.     

基于粗粒度可重构阵列结构的多标准离散余弦变换设计

在视频信号的编解码流程中,离散余弦变换(DCT)是一个至关重要的环节,其决定了视频压缩的质量和效率。针对88尺寸的2维离散余弦变换,该文提出一种基于粗粒度可重构阵列结构(Coarse-Grained Reconfigurable Array, CGRA)的硬件电路结构。利用粗粒度可重构阵列的可重配置的特性,实现在单一平台支持多个视频压缩编码标准的88 2维离散余弦变换。实验结果显示,这种结构每个时钟周期可以并行处理8个像素,吞吐率最高可达1.157109像素/s。与已有结构相比,设计效率和功耗效率最高可分别提升4.33倍和12.3倍,并能够以最高30帧/s的帧率解码尺寸为40962048,格式为4:2:0的视频序列。     

Hybrid picture coding with wavelet transform and overlappedmotion-compensated interframe prediction coding

A novel video coding scheme using an orthonormal wavelet transform is proposed. The wavelet transform is used in a motion compensated interframe coder in which a blockless motion compensation technique is employed to increase efficiency of wavelet transform coding. A new scanning method for wavelet coefficients is also proposed which is rather different from subband coding. Simulation work is carried out to evaluate the proposed coding method. Significant improvement in subjective quality is obtained over that obtained with conventional hybrid coding methods that use blockwise motion compensation and DCT. Some improvement has also been realized in the signal to noise ratio. Although wavelet coding is still in its early stages of development, it appears to hold great promise for motion picture coding     

基于多线性子空间KL变换的可伸缩视频压缩方法

该文提出一种基于多线性子空间KL(Karhunen-Loeve)变换的可伸缩视频压缩算法。该算法将纹理不同的图像子块投影到多个线性子空间中去,然后分别进行KL变换编码,使得每个子空间内变换系数更接近高斯分布,从而最大限度地在变换编码阶段提高压缩效率。同时,该算法结合多尺度小波分解,实现了质量可伸缩的视频编码,提高了视频压缩率。通过与DCT、小波变换以及多向DCT算法进行比较,证明该算法可获得更好的率失真性能。     

Novel distribution model of transformed coefficients in video coding using quad-tree structured block partitioning

Today’s video coding standard such as high efficiency video coding uses a full quad-tree structured block partitioning, so the underlying statistics of transformed coefficients becomes more complicated to estimate than the previous standards due to the coding structure. However, a statistical distribution of transformed residue is important for a design of a smart encoder. Thus, in this paper, we present a theoretic analysis of a distribution of transformed coefficients produced from an encoder using different transform sizes, and derive a probability density function (pdf) for the estimation. The proposed density model provides a more accurate distribution model than the conventional pdfs. Parameters are theoretically estimated, and rate-distortion model is established from the proposed pdf. We also apply the proposed method to a rate control problem to show the efficiency of the proposed density model. Our experimental results show that the proposed method is better capable of modeling the mixed sources of multiple-type transform coefficients occurred from the quad-tree coding structure of transform and provides an accurate estimate in rate control.

     

Entropy Coding for a Hybrid Scheme with Motion Compensation in Subprimary Rate Video Transmission

Entropy coding has been investigated for motion-compensated interframe (MC) prediction followed by two-dimensional discrete cosine transform (DCT) for prediction error. In particular, variable word length coding methods for motion vector and transform coefficients have been discussed assuming low bit rate such as 384 kbits/s for transmission of videoconference sequences. For motion vector information, it is advantageous to employ a one-dimensional code set common to both horizontal and vertical components of motion vectors. The code set can be obtained using a combined distribution of the two components. In order to encode transform coefficients, different methods are applied to significant and insignificant blocks. Run-length coding is adequate for representing clusters of insignificant blocks. In encoding transform coefficients in significant blocks, a zone coding method which encodes transform coefficients within a minimum area enclosing all nonzero coefficients is suitable. Simulation of video sequences shows that a combination of the coding methods described here can achieve high coding efficiency for videoconference sequences.     

Scalable Interframe Wavelet Coding with Low Complex Spatial Wavelet Transform

In the decoding process associated with interframe wavelet coding, the inverse wavelet transform requires high computational complexity. However, as video technology starts to pervade all aspects of our lives, decoders are becoming required in various devices such as PDAs, notebooks, PCs, and set‐top boxes. Therefore, a decoder's complexity needs to be adapted to the processor's computational power, and consequently a low‐complexity codec is also required for scalable video coding. In this paper, we propose a method of controlling and lowering the complexity of the spatial wavelet transform while sustaining the same coding efficiency as that currently afforded. In addition, the proposed method may alleviate the ringing effect for slowly changing image sequences.     

Quadtree-based non-local Kuan’s filtering in video compression

Transform coding has been widely used in video coding standards, such as H.264 advanced video coding (H.264/AVC) and high efficiency video coding (HEVC). But the coded video sequences suffer from annoying coding artifacts, such as blocking and ringing artifacts. In this paper, we propose the quadtree-based non-local Kuan’s (QNLK) filter to suppress the quantization noise optimally and improve the objective and subjective quality of the reconstructed frame simultaneously. The proposed filter takes advantage of the non-local Kuan’s (NLK) filter to restore the quantized signal in transform domain. Restored coefficients are then projected onto designed quantization constraint sets (QCS). Quadtree-based signaling strategy is used at the end of QNLK for adaptive filtering on/off control. Experimental results of QNLK show that the proposed method achieves significant objective coding gain and visual quality improvement, compared with both H.264/AVC high profile and HEVC.     

Low bit-rate video coding using wavelet vector quantisation

A method for low bit-rate video coding based on wavelet vector quantisation is proposed. Motion estimation/compensation using overlapped block matching (OBM) is employed to eliminate the blocking effects in the prediction error introduced by conventional block matching. It is shown that OBM significantly increases the efficiency of the wavelet transform coder. The motion-compensated interframe prediction error is decomposed using a wavelet transform and a method is employed for the efficient coding of the wavelet coefficients. In this technique, the coefficients are coded with a zero-tree multistage lattice vector quantiser. Simulation results are provided to evaluate the coding performance of the described coding scheme for low bit-rate video coding. It provides constant bit rate, obviating the need for buffer, with just small fluctuations in PSNR. Moreover, comparison with the RM8 implementation of the standard H261 video coder shows that the presented codec provides improvements in both peak signal-to-noise ratio and picture quality