视频编码技术的新发展

介绍了视频编码技术的新成果:H.26L建议。回顾视频标准和建议的发展历史,介绍了H.26L的技术背景和视频编码技术,总结了H.26L的特性,探讨了该标准的应用前景。     

H.264可分级编码技术介绍

H.264标准以其高效的编解码技术,为视频编码的发展带来了革命性的变化。近年来,随着视频业务的增多,相关的分级编码技术不断发展。为了适应需求,H.264标准也增加了可分级编码的扩展部分。本文首先简要回顾了H.264标准的相关概念,然后对H.264标准的时域、空域和质量可分级编码作了介绍和分析。最后揭示了各种分级编码技术的特点。     

3种主流HDTV压缩编码方法的比较

基于MPEG-4、H.264 High Profile及H.264 Main Profile等3种视频压缩编码方法,对HDTV(高清晰度电视)视频压缩标准中的算法进行了详细的分析和测试,分别从编码对象的率失真曲线、编码速度和High Profile在不同量化步长下的主观图像质量对3种压缩编码方法进行比较分析.测试结果表明:H.264 High Profile编码复杂度比MPEG-4提高了6倍～9倍,比H.264 Main Profile提高了20%～50%;从最佳编码性能角度考虑,H.264 High Profile是最适合于标清和高清晰度序列的编码方案.     

视频压缩编码国际标准综述

国际标准化组织和国际电信联盟制定了一系列视频压缩编码国际标准,有H.261,MPEG1,MPEG2, H.263, MPEG4和H.264等.该文分别对这些标准的技术特征和性能进行分析,并详细描述H.264中采用的视频编码新技术.     

一种新的视频编码标准——H.26L

H．26L标准是ITU－T正在制定中的新的图像压缩标准。它在H．263的基础上，编码算法有很大的改进，编码效率有很大的提高。文中介绍了H．26L的功能和应用范围，然后与H．263相比较，分析了其先进之处，最后介绍了它在移动通信系统中的应用。     

H.26L中熵编码原理分析及改进

分析了H.26L中熵编码的原理和特点,比较了两种不同熵编码方法的优缺点、性能差异和发展方向,提出了一种基于量化参数QP的熵编码改进方法。实验证明这种方法能在信道传输率变化到一定程度时,动态调整熵编码的方法,使H.26L熵编码器在复杂度和编码效率两方面作出合理的权衡。     

H.26L甚低码率视频压缩标准的性能分析

H．26L是VCEG(视频编码专家组)制定的新的甚低码率图像压缩标准，主要应用于可视电话和网络视频传输。本文讨论了H．26L的编码原理及其相对于H．263视频编码标准的新发展，分析了该标准的优点及实用化遇到的问题。计算机对比实验表明H．26L通过采用1，4精度运动估计、增强的先进帧间预测编码和帧内预测编码．在保证图像质量的情况下，压缩码率有明显改善，但同时运算的复杂度也大大增加。     

数字电视信源编码的主要技术与标准

介绍了数字电视信源编码的主要技术和标准,包括数字演播室标准ITU-601,压缩编码的基本原理和方法,图像压缩编码标准H.261,JPEG和MPEG,以及作为数字电视信源编码标准输出的MPEG-2码流的形成.     

数字电视信源编码的主要技术与标准

介绍了数字电视信源编码的主要技术和标准,包括数字演播室标准ITU-601,压缩编码的基本原理和方法,图像压缩编码标准H.261,JPEG和MPEG,以及作为数字电视信源编码标准输出的MPEG-2码流的形成.     

数字电视信源编码的主要技术与标准

介绍了数字电视信源编码的主要技术和标准,包括数字演播室标准ITU-601,压缩编码的基本原理和方法,图像压缩编码标准H. 261,JPEG和MPEG,以及作为数字电视信源编码标准输出的MPEG-2码流的形成。     

Layered Wyner–Ziv Video Coding

Following recent theoretical works on successive Wyner-Ziv coding (WZC), we propose a practical layered Wyner-Ziv video coder using the DCT, nested scalar quantization, and irregular LDPC code based Slepian-Wolf coding (or lossless source coding with side information at the decoder). Our main novelty is to use the base layer of a standard scalable video coder (e.g., MPEG-4/H.26L FGS or H.263+) as the decoder side information and perform layered WZC for quality enhancement. Similar to FGS coding, there is no performance difference between layered and monolithic WZC when the enhancement bitstream is generated in our proposed coder. Using an H.26L coded version as the base layer, experiments indicate that WZC gives slightly worse performance than FGS coding when the channel (for both the base and enhancement layers) is noiseless. However, when the channel is noisy, extensive simulations of video transmission over wireless networks conforming to the CDMA2000 1X standard show that H.26L base layer coding plus Wyner-Ziv enhancement layer coding are more robust against channel errors than H.26L FGS coding. These results demonstrate that layered Wyner-Ziv video coding is a promising new technique for video streaming over wireless networks     

Layered Wyner-Ziv video coding.

Following recent theoretical works on successive Wyner-Ziv coding (WZC), we propose a practical layered Wyner-Ziv video coder using the DCT, nested scalar quantization, and irregular LDPC code based Slepian-Wolf coding (or lossless source coding with side information at the decoder). Our main novelty is to use the base layer of a standard scalable video coder (e.g., MPEG-4/H.26L FGS or H.263+) as the decoder side information and perform layered WZC for quality enhancement. Similar to FGS coding, there is no performance difference between layered and monolithic WZC when the enhancement bitstream is generated in our proposed coder. Using an H.26L coded version as the base layer, experiments indicate that WZC gives slightly worse performance than FGS coding when the channel (for both the base and enhancement layers) is noiseless. However, when the channel is noisy, extensive simulations of video transmission over wireless networks conforming to the CDMA2000 1X standard show that H.26L base layer coding plus Wyner-Ziv enhancement layer coding are more robust against channel errors than H.26L FGS coding. These results demonstrate that layered Wyner-Ziv video coding is a promising new technique for video streaming over wireless networks.     

H.26L性能分析与算法优化

在相同的码率控制策略的最优参数配置下，对H．26L，MPGE－4 ASP校验模型系统进行计算机仿真，实验表明，对于CIF和QCIF格式的图像，在压缩效率上H．26L要高于MPGE－4 ASP。相同峰值信噪比条件下，H．26L目标码率约为MPEG－4 ASP的1／3－1／5，然而H．26L的运算复杂也远高于MPEG－4 ASP。本文采用整像素和亚像素运动估值的快速算法，使运算复杂度的约降低到原来的1／3。     

提高H.26L压缩视频抗误码性能的全局率失真优化方法

该文从较新的H.26L视频压缩编码标准出发,并结合Internet信道的Bernoulli和Gilbert 的包丢失模型,提出了一种全局率失真优化的编码模式判决方法,使编码的视频流具有更强的错误恢复能力。实验证明,在实际的Internet信道误码环境下,此方法具有更强的抗错误和实用性,得到了较好的效果。     

H.26L中基于双线性和立方卷积的混合插值算法

本文根据对H.26L视频编码算法的研究,提出一种基于双线性和立方卷积的混合插值算法.通过分析比较H.26L中的双线性插值和立方卷积插值,指出单一插值算法的局限性,并在H.26L软件编解码中实现了混合插值算法.实验表明,该算法可以较大幅度改善主客观图像质量,提高图像压缩编码效率.     

Comparison of H.263 and H.26L video compression performance with web-cams

The results of a comparison of the compression efficiency of the H.263 and H.26L algorithms are presented when used to compress video from a variety of cameras. It is shown that H.26L achieves better compression performance in most cases, with larger compression gains being achieved when higher quality cameras are used.     

H．26L标准中1／4像素精度运动估计的优化

为了提高H．26L中1／4像素精度运动估计的速度，提出了基于快速SAD(Sums of Absolute Difference)优化算法。这种算法在保证图像质量的前提下，使H．26L视频编码的速度大大提高。     

All zero macroblock decision method for H.26L

In order to reduce the computation in the part of motion search and transform in H.26L encoder, an all-zero macroblock decision method based on integer transform and motion search is proposed in this paper. According to the characteristics of integer transform and motion search in H.26L, all-zero macroblock decision is made in inter frame coding by comparing Sum of the Absolute Differences(SAD) with a value related with Quantization Parameter(QP) before integer transform. It avoids a large amount of computation in motion search, transform and quantization. This technology highly improves the efficiency of real time H.26L encoder by skipping all-zero macroblock before integer transform and shortening the code stream at the same time.