AVS中的音视频编码压缩技术

介绍了音视频编码标准AVS中的主要技术特点,对AVS标准所采用的主要技术进行了综述,给出了AVS视频标准与MPEG-4 AVC/H.264编码器性能的比较和分析,讨论了AVS的发展前景.     

MPEG解决方案：向H．264视频压缩过渡

H．264是ITU—T的VCEG（视频编码专家组）和ISO／IEC的MPEG（活动图像编码专家组）的联合视频组（JVT：jointvideoteam）制定和发布的目前国际上最新的数字视频编码标准,是目前视频图像研究领域的热点问题之一。H．264视频编码标准可满足多种应用需求,其在数字视频通信和存储领域得到越来越广泛的应用。     

Highly Efficient Video Codec for Entertainment‐Quality

We present a novel video codec for supporting entertainment‐quality video. It has new coding tools such as an intra prediction with offset, integer sine transform, and enhanced block‐based adaptive loop filter. These tools are used adaptively in the processing of intra prediction, transform, and loop filtering. In our experiments, the proposed codec achieved an average reduction of 13.35% in BD‐rate relative to H.264/AVC for 720p sequences.     

Video transcoding from H.264/AVC to MPEG-2 with reduced computational complexity

This paper addresses video transcoding from H.264/AVC into MPEG-2 with reduced complexity and high rate-distortion efficiency. While the overall concept is based on a cascaded decoder–encoder, the novel adaptation methods developed in this work have the advantage of providing very good performance in H.264/AVC to MPEG-2 transcoding. The proposed approach exploits the similarities between the coding tools used in both standards, with the objective of obtaining a computationally efficient transcoder without penalising the signal quality. Fast and efficient methods are devised for conversion of macroblock coding modes and translation of motion information in order to compute the MPEG-2 coding format with a reduced number of operations, by reusing the corresponding data embedded in the incoming H.264/AVC coded stream. In comparison with a cascaded decoder–encoder, the fast transcoder achieves computational complexity savings up to 60% with slightly better peak signal-to-noise ratio (PSNR) at the same bitrate.     

SSIM-based error-resilient rate-distortion optimization of H.264/AVC video coding for wireless streaming

The SSIM-based rate-distortion optimization (RDO) has been verified to be an effective tool for H.264/AVC to promote the perceptual video coding performance. However, the current SSIM-based RDO is not efficient for improving the perceptual quality of the video streaming application over the error-prone network, because it does not consider the transmission induced distortion in the encoding process. In this paper, a SSIM-based error-resilient RDO scheme for H.264/AVC is proposed to improve the wireless video streaming performance. Firstly, with the help of the SSE-based RDO, we present a low-complexity Lagrange multiplier decision method for the SSIM-based RDO video coding in the error-free environment. Then, the SSIM-based decoding distortion of the user end is estimated at the encoder and is correspondingly introduced into the RDO to involve the transmission induced distortion into the encoding process. Further, the Lagrange multiplier is theoretically derived to optimize the encoding mode selection in the error-resilient RDO process. Experimental results show that the proposed SSIM-based error-resilient RDO can obtain superior perceptual video quality (more structural information) to the traditional SSE-based error-resilient RDO for wireless video streaming at the same bit rate condition.     

MPEG-4解码器芯片的比较

介绍了目前市场上比较流行的一些MPEG-4编解码芯片，比较了它们的应用前景和特性，并简要介绍了新一代视频编解码标准H．264的芯片产品。     

IPTV技术标准与应用前景

介绍IPTV的概念及技术标准，重点介绍主流的3大音视频编解码技术标准MPEG-4，H-264／AVC和AVS及其应用前景。     

Fast motion estimation for H.264

Several specific features have been incorporated into Motion estimation (ME) in H.264 coding standard to improve its coding efficiency. However, they result in very high computational load. In this paper, a fast ME algorithm is proposed to reduce the computational complexity. First, a mode discriminant method is used to free the encoder from checking the small block size modes in homogeneous regions. Second, a condensed hierarchical block matching method and a spatial neighbor searching scheme are employed to find the best full-pixel motion vector. Finally, direction-based selection rule is utilized to reduce the searching range in sub-pixel ME process. Experimental results on commonly used QCIF and CIF format test sequences have shown that the proposed algorithm achieves a reduction of 88% ME process time on average, while incurring only 0.033 dB loss in PSNR and 0.50% increment on the total bit rate compared with that of exhaustive ME process, which is a default approach adopted in the JM reference software.     

x264视频编码器中参数设置对编码效率影响的研究

x264是基于H.264/MPEG-4 AVC视频压缩标准的视频压缩编码器,它提供了很多可以设置的参数来控制其编码效率。不同的参数设置影响着编码时间,压缩后的视频大小和视频质量。文章分别比较和分析了一些编码参数,包括图像组、帧内预测的宏块分割、帧间预测的宏块分割、参考帧数目和像素精度对视频的平均每帧编码时间、平均每帧大小和平均峰值信噪比带来的影响。     

IPTV技术标准与应用前景

介绍IPTV的概念及技术标准,重点介绍主流的3大音视频编解码技术标准MPEG-4,H.264/AVC和AVS及其应用前景。     

视频压缩标准的最新进展

视频压缩是多媒体应用系统中一个十分重要的组成部分。阐述现今普遍采用的基于块的运动补偿和变换编码混合视频编码技术，对该系统中的每个部分进行了描述。分析ISO和ITU两大国际标准组织最新联合发布的H．264／AVC视频压缩标准，指出该视频压缩方式同以往的标准存在的显著不同，并就压缩性能同以往的标准进行对比。     

流媒体应用中TS和MP4格式分析

新一代视频编码标准H．264／AVC具有编码效率高，容错性强等特点，在流媒体传输应用方面有广阔的应用前景。介绍了一种典型的流媒体传输基本框架，对基本传输过程进行了介绍，分析了其中可能存在的问题，特别是传输和存储格式方面并根据通用的MP4和MPEG-2TS格式围绕着复用、同步、打包问题进行了重点研究。     

H.264编/解码器中去块效应滤波系统的设计

提出了一种针对H.264/MPEG-4 AVC标准的高性能低复杂度的去块效应滤波系统的VLSI结构,该结构利用数据重用机制以减少数据的吞吐量,同时辅以高效的数据流控制和并行计算.在100MHz的情况下,该结构满足1920×1088@30Hz的高清晰度视频编解码要求.     

Frame distortion estimation for unequal error protection methods in scalable video coding (SVC)

In many multimedia applications, coded video is transmitted over error prone heterogeneous networks. Because of the predictive mechanism used in video coding, transmission error would propagate temporally and spatially and would result in significant quality losses. In order to address this problem, different error resilience methods have been proposed. One of the techniques, which is commonly used in video streaming, is unequal error protection (UEP) of scalable video coding (SVC). In this technique, different independent layers of an SVC stream are protected differently and based on their importance by using forward error correction (FEC) codes. Accurately analyzing the importance or utility of each video part is a critical component and would lead to a better protection and higher quality of the received video. Calculation of the utility is usually based on multiple decoding of sub-bitstreams and is highly computationally complex. In this work, we propose an accurate low complexity utility estimation technique that can be used in different applications. This technique estimates the utility of each network abstraction layer (NAL) by considering the error propagation to future frames. We utilize this method in an UEP framework with the scalable extension of H.264/AVC codec and it achieves almost the same performance as highly complex estimation techniques (an average loss of 0.05 dB). Furthermore, we propose a low delay version of this technique that can be used in delay constrained application. The estimation accuracy and performance of our proposed technique are studied extensively.     

基于SoC平台的H.264/MPEG-4 AVC解码器设计

提出了一种基于SoC平台的H.264/MPEG-4 AVC解码器设计方案,该方案基于Gaisler Research开发的LEON3 RISC核,采用双总线的流水线结构,具有很高的性价比,通过在Modelsim 6.0下的仿真结果表明,硬件解码部分在200 MHz系统时钟时可以实时解码H.264 High 44 4 profile 4.0 level码流.     

Mode dependent down-sampling and interpolation scheme for high efficiency video coding

In this paper, a mode dependent down-sampling and interpolation scheme is proposed to improve the coding efficiency of the intra prediction module. In the proposed method, we elaborately design the down-sampling structures and interpolation schemes for each directional intra prediction mode by minimizing the spatial prediction distance. The sampled pixels are predicted with a traditional directional intra prediction scheme, and the non-sampled pixels are predicted from the interpolation of their neighboring reconstructed sampling pixels. Both the residuals of the sampled and non-sampled pixels are encoded at last. Experimental results show that the proposed method achieves an average 7.52% bitrate reduction relative to KTA reference software. Since the down-sampling structure and interpolation method is only related to the intra mode, there is no additional overhead at the encoder.     

VLSI Architecture Design of Fractional Motion Estimation for H.264/AVC

The H.264/AVC Fractional Motion Estimation (FME) with rate-distortion constrained mode decision can improve the rate-distortion efficiency by 2–6 dB in peak signal-to-noise ratio. However, it comes with considerable computation complexity. Acceleration by dedicated hardware is a must for real-time applications. The main difficulty for FME hardware implementation is parallel processing under the constraint of the sequential flow and data dependency. We analyze seven inter-correlative loops extracted from FME procedure and provide decomposing methodologies to obtain efficient projection in hardware implementation. Two techniques, 4×4 block decomposition and efficiently vertical scheduling, are proposed to reuse data among the variable block size and to improve the hardware utilization. Besides, advanced architectures are designed to efficiently integrate the 6-taps 2D finite impulse response, residue generation, and 4×4 Hadamard transform into a fully pipelined architecture. This design is finally implemented and integrated into an H.264/AVC single chip encoder that supports realtime encoding of 720×480 30fps video with four reference frames at 81 MHz operation frequency with 405 K logic gates (41.9% area of the encoder).

视频编码新标准H.264/AVC中的重要技术

简要介绍了最新的视频编码标准H．264／AVC的制定情况，详细叙述了H．264／AVC基本框架中采用的几个重要技术，最后比较了H．264／AVC和已有的几个编码标准的性能，H．264／AVC的压缩性能最好。     

Engineering wireless broadband access to IPTV

IPTV is now extending to wireless broadband access. If broadband video streaming is to achieve competitive quality the video stream itself must be carefully engineered to cope with challenging wireless channel conditions. This paper presents a scheme for doing this for H.264/AVC codec streaming across a WiMAX link. Packetization is an effective tool to govern error rates and, in the paper, source-coded data-partitioning serves to allocate smaller packets to more important data. A packetization strategy is insufficient in itself, as temporal error propagation should also be addressed by insertion of intra-coded data. It may be necessary to include redundant packets when channel conditions worsen. The whole should be protected by application-layer rateless coding. Therefore, the contribution of the paper is a complete scheme comprised of various protection measures aimed at robust IPTV streaming. Due to computational overheads, the scheme is aimed at the new generation of smartphones with GHz CPUs.     

Perceptually driven video error protection using a distributed source coding approach

In video communication systems, the video signals are typically compressed and sent to the decoder through an error-prone transmission channel that may corrupt the compressed signal, causing the degradation of the final decoded video quality. In this context, it is possible to enhance the error resilience of typical predictive video coding schemes using as inspiration principles and tools from an alternative video coding approach, the so-called Distributed Video Coding (DVC), based on the Distributed Source Coding (DSC) theory. Further improvements in the decoded video quality after error-prone transmission may also be obtained by considering the perceptual relevance of the video content, as distortions occurring in different regions of a picture have a different impact on the user's final experience. In this context, this paper proposes a Perceptually Driven Error Protection (PDEP) video coding solution that enhances the error resilience of a state-of-the-art H.264/AVC predictive video codec using DSC principles and perceptual considerations. To increase the H.264/AVC error resilience performance, the main technical novelties brought by the proposed video coding solution are: (i) design of an improved compressed domain perceptual classification mechanism; (ii) design of an improved transcoding tool for the DSC-based protection mechanism; and (iii) integration of a perceptual classification mechanism in an H.264/AVC compliant codec with a DSC-based error protection mechanism. The performance results obtained show that the proposed PDEP video codec provides a better performing alternative to traditional error protection video coding schemes, notably Forward Error Correction (FEC)-based schemes.