基于宏块内部特征的H.264快速预测模式决策算法*

为了提高视频质量、降低码率,H.264/AVC采用了七种块划分类型,使得在提高编码性能的同时带来了高计算复杂度。研究了宏块的内部特征,提出了一种基于宏块内部信息复杂度的快速帧间模式选择算法。实验数据表明,在保证重建图像信噪比的情况下,该算法降低了帧间预测的复杂度,可平均节省17%24%的编码时间,满足了实时视频通信的要求。     

Simplified algorithms for rate-distortion optimization in high efficiency video coding

HEVC is the latest coding standard to improve the coding efficiency by a factor of two over the previous H.264/AVC standard at the cost of the increased complexity of computation rate-distortion optimization (RDO) is one of the computationally demanding operations in HEVC and makes it difficult to process the HEVC compression in real time with a reasonable computing power. This paper aims to present various simplified RDO algorithms with the evaluation of their RD performance and computational complexity. The algorithms for the simplified estimation of the sum of squared error (SSE) and context-adaptive binary arithmetic coding (CABAC) proposed for H.264/AVC are reviewed and then they are applied to the simplification of HEVC RDO. By modifying the previous algorithm for H.264/AVC, a new simplified RDO algorithm is proposed for modifying the previous algorithm for H.264/AVC to be optimized for the hierarchical coding structure of HEVC. Further simplification is attempted to avoid the transforms operations in RDO. The effectiveness of the existing H.264/AVC algorithms as well as the proposed algorithms targeted for HEVC is evaluated and the trade-off relationship between the RD performance and computational complexity is presented for various simplification algorithms. Experimental results show that reasonable combinations of RDO algorithms reduce the computation by 80–85% at the sacrifice of the BD-BR by 3.46–5.93% for low-delay configuration.     

H.264/AVC中基于决策树的P帧快速模式选择

目的 H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。为此提出一种针对P帧的基于决策树的快速候选模式选择算法。方法在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的变换域系数绝对值之和(SATD)值,采用决策树分类方法对其余宏块选择候选模式。结果由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间的节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

An Efficient Mode Decision Algorithm for H.264/AVC Encoding Optimization

The H.264 video coding standard significantly outperforms previous standards in terms of coding efficiency. However, this comes as a cost of extremely high computational complexity due to mode decision where variable block size motion estimation (ME) is employed. In this paper, we propose an efficient algorithm to jointly optimize mode decision and ME. A theoretical analysis is performed to study the sufficient condition to detect all-zero blocks in H.264, and thus adaptive thresholds are derived to early terminate mode decision and ME. Besides the aforementioned early termination technique, the proposed algorithm also introduces temporal-spatial checking, thresholds based prediction and monotonic error surface based prediction methods to skip checking unnecessary modes. Experimental results demonstrate that the proposed algorithm can significantly reduce the computational complexity of H.264 encoding while maintaining almost the same rate distortion (RD) performance as the original encoder     

H.264/AVC编码模式选择

H．264／AVC是最新的视频编码标准。与以前的视频标准相比编码模式更多,压缩效率更高,同时在编码模式的选择上也更复杂,计算量更大。编码时如何选择合适的编码模式对H.264／AVC的压缩性能和计算复杂度是非常关键的。本文讲述了JVT的参考软件是如何实现H．264／AVC编码模式选择。     

A dynamically reconfigurable processor for H.264/AVC image prediction

H.264/AVC provides high video quality at substantially low bit rates. It is useful for saving and transferring video images by robot cameras. However, the computational complexity of H.264/AVC is very high. A high-speed general-purpose processor is necessary to process H.264/AVC. However, it is difficult to use such a processor for a portable device. Therefore, an application-specific processor is necessary. A dynamic reconfiguration can virtually expand the circuit area in a limited chip area. Therefore, this article proposes a dynamically reconfigurable processor for H.264/AVC image prediction. H.264/AVC contains intra- and inter-prediction processes. The intra- and inter-prediction processes are not used at the same time. The proposed processor was designed and synthesized, and dynamically reconfigures those circuits. As a result, look-up tables (LUTs) were reduced to 93%, flip-flops were reduced to 94%, and the maximum delay was about the same.     

HEVC 熵编码算法优化

新一代视频编码标准HEVC提供了更加灵活的编码工具选择,在提高压缩率的同时也提高了编码的计算复杂度。由于可选择更大的变换单元以及编码中更强的系数间依赖关系,在率失真优化（RDO）模式选择过程中,HEVC熵编码的计算复杂度显著高于H．264/AVC。为了解决这一问题,本文对HEVC熵编码算法进行优化,通过优化熵编码的上下文空间选择过程、非零系数的编码结构,以及对不同大小的变换矩阵进行整体优化。实验结果表明,本文提出的优化算法能够在保证视频编码质量基本不变的同时,平均降低约43％的熵编码时间。     

Fast transcoding from H.264 to HEVC based on region feature analysis

The new video coding standard, High Efficiency Video Coding (HEVC), achieves much higher coding efficiency than the state-of-the-art H.264. Transcoding H.264 video to HEVC video is important to enable gradual migration to HEVC. Therefore, a fast H.264 to HEVC transcoding algorithm based on region feature analysis is proposed. First, each frame is segmented into three regions in units of coding tree unit (CTU) based on the correlation between image coding complexities and coding bits of the H.264 source stream. Then the searching depth range of each CTU is adaptively decided according to the region type. After that, motion vectors are de-noise filtered and clustered in order to analyze the region features of coding unit (CU). Based on the analysis results, the minimum searching depth of CU and partitions of prediction unit (PU) are optimally selected, and the motion vector predictor and search window size of motion estimation are also optimally decided for further reduction of the computational complexity. Experimental results show that the proposed algorithm achieves a significant improvement on transcoding speed, while maintaining high Rate-Distortion performance.     

H.264/AVC中基于决策树的P帧快速模式选择（HHME2013第61号论文）

目的：H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。本文提出了一种针对P帧的基于决策树的快速选择候选模式算法。方法：在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的SATD值,采用决策树分类方法对其余宏块选择候选模式。结果：由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论：本文提出了一种新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

A fast DEA-based intra-coding algorithm for HEVC

As the newest video coding standard, High Efficiency Video Coding (HEVC) greatly enhances the encoding performance of H.264/AVC. However, HEVC also has high computational complexity, which limits application of this new standard. In this paper, we propose a fast DEA-based intra-coding algorithm, including block partitioning; prediction mode selection and edge offset (EO) class decision algorithms. The idea behind the proposed algorithm is to utilize the texture characteristics of the encoding image, which are quantified by dominant edge assent (DEA) and its distribution, to reduce the decision space. Specifically, for block partitioning, we propose the most possible depth range (MPDR) and employ DEA to determine whether the current coding block can use the MPDR to predict the partitioning depth or not; for intra-prediction mode selection, we use DEA and its distribution to reduce the range of prediction direction; for the EO class decision, we use DEA to determine the EO class of the sample adaptive offset. We integrate the proposed algorithm into the test model HM 13.0 and present a detailed comparative analysis. Experimental results show that the proposed fast DEA-based intra-coding algorithm reduces the computational complexity of HM 13.0 to about 46% in encoding time with 2.08% increases in the Biontegaard-Delta bitrate (BD-rate). Moreover, the proposed algorithm also demonstrates better performance over other state-of-the-art work.     

H.264快速模式确定方法

H.264/AVC是最新的视频编码标准,与以前的视频标准相比编码效率最多提高了50%。与此同时,H.264编码器的计算复杂度也比H.263提高了约3倍。这对于资源受限的应用系统来说是个巨大的挑战。分析发现,H.264编码器中宏块的模式确定占了编码时间的90%左右。论文提出了一种简单而有效的快速模式确定方法,模拟试验的结果表明,该方法在编码性能几乎没有降低的情况下,总体编码时间比传统方法减少了50%以上。     

Fast coding unit (CU) determination algorithm for high-efficiency video coding (HEVC) in smart surveillance application

High-efficiency video coding (HEVC) is a successor to the H.264/AVC standard as the newest video-coding standard using a quad-tree structure with the three block types of a coding unit (CU), a prediction unit (PU), and a transform unit (TU). This has become popular to apply to smart surveillance systems, because very high-quality image is needed to analyze and extract more precise features. On standard, the HEVC encoder uses all possible depth levels for determination of the lowest rate-distortion (RD) cost block. The HEVC encoder is more complex than the H.264/AVC standard. An efficient CU determination algorithm is proposed using spatial and temporal information in which 13 neighboring coding tree units (CTUs) are defined. Four CTUs are temporally located in the current CTU and the other nine neighboring CTUs are spatially situated in the current CTU. Based on the analysis of conditional probability values for SKIP and Merge modes, an optimal threshold value was determined for judging SKIP or Merge mode according to the CTU condition and an adaptive weighting factor. When SKIP or Merge modes were detected early, other mode searches were omitted. The proposed algorithm achieved approximately 35 % time saving with random-access configuration and 29 % time reduction with low-delay configuration while maintaining comparable rate-distortion performance, compared with HM 12.0 reference software.     

Fast HEVC I-frame coding based on strength of dominant direction of CUs

High efficiency video coding (HEVC), the latest international video coding standard, greatly outperforms previous standards such as H.264/AVC in terms of coding bitrate and video quality. The coding efficiency improvement in HEVC is achieved by introducing several new techniques such as recursive quad-tree structure and increased number of intra prediction modes. However, computational load is also increased due to employing the new techniques. In this paper, we propose a solution for fast I-frame coding in HEVC standard using homogeneity of Coding Units (CUs). The proposed solution consists of two stages. In the first stage, we evaluate CU homogeneity by computing a parameter named dominant direction strength and predict CU size by this means. In the second stage, we select 11 modes out of 35 for the specified CU size based on dominant direction of the CU. Experimental results indicate that the proposed method achieves on average 45.8 % reduction on coding time, with very similar coding efficiency as the HEVC reference software. Moreover, we designed tree-stage pipelined architecture for our method which can operate at 235 MHz maximum clock rate which means it can be used for real-time coding of all intra configuration of HEVC videos up to level 6.2.     

HEVC optimization based on human perception for real-time environments

High-Efficiency Video Coding (HEVC) is the new emerging video coding standard of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). The HEVC standard provides a significant improvement in compression efficiency in comparison with existing standards such as H264/AVC by means of greater complexity. In this paper we will examine several HEVC optimizations based on image analysis to reduce its huge CPU, resource and memory expensive encoding process. The proposed algorithms optimize the HEVC quad-tree partitioning procedure, intra/inter prediction and mode decision by means of H264-based methods and spatial and temporal homogeneity analysis which is directly applied to the original video. The validation process of these approaches was conducted by taking into account the human visual system (HVS). The adopted solution makes it possible to perform HEVC real time encoding for HD sequences on a low cost processor with negligible quality loss. Moreover, the frames pre-processing leverages the logic units and embedded hardware available on an Intel GPU, so the execution time of these stages are negligible for the encoding processor.

     

基于运动复杂度的快速模式选择算法

H.264/AVC是ITU-T和ISO/IEC联合制定的最新视频压缩标准。它采用了可变块运动估计和率失真优化模式判决。H.264需要对10 种模式进行率失真优化计算才能得到一个宏块的最优编码模式,极大地增加了编码器的复杂度。为了提高模式选择效率,提出了一种基于运动复杂度的快速模式选择算法。实验结果表明,在PSNR仅有微小下降情况下,该算法可大幅提升编码速度。     

符合H.264标准的一种基于内容的变尺寸宏块分割方法

提出了一种基于视频内容预分析的变尺寸宏块分割(CBVSBM)的实现方案,变尺寸宏块分割是H.264编码器端提供的重要编码工具。该方案根据每帧视频的内容,自适应地在自顶向下的变尺寸运动估计(TDVSBM)和自底向上的变尺寸运动估计(BUVSBM)两种变尺寸宏块分割算法(VSBM)间进行切换,从而结合了两种算法的优点。为了实现两种VSBM算法间的自适应选择,提出了一种简单而有效的基于STGS图的预判准则。理论分析和实验结果表明,该算法的运算复杂度低于TDVSBM和BUVSBM,而在视频质量上总是优于TDVSBM且与BUVSBM几乎相当。     

Fast multiframe motion estimation algorithms by motion vector composition for the MPEG-4/AVC/H.264 standard

The MPEG-4/AVC/H.264 video coding standard adopts various coding schemes such as multiple reference frames and variable block sizes for motion estimation. Hence, MPEG-4/AVC/H.264 provides gains in compression efficiency of up to 50% over a wide range of bit rates and video resolutions compared to previous standards. However, these features result in a considerable increase in encoder complexity, mainly regarding to mode decision and motion estimation. The proposed algorithms use the stored motion vectors to compose the motion vector without performing the full search in each reference frame. Therefore, the proposed algorithms can obtain an average speed up ratio of four for encoding, thus benefiting from the prediction of the motion vector for the reference frames in advance and maintaining good performance. Any fast search algorithm can be utilized to further largely reduce the computational load.     

H.264帧内预测模式选择的快速算法分析

帧内预测是H.264/AVC的一个重要组成部分,它充分利用了图像的空间相关性,提高了压缩效率,对编码器的整体性能提高具有重要作用。然而其运算复杂度很高,不能满足实时视频的要求。因此,近几年很多文章提出了H.264帧内预测模式选择的快速算法,它们对H.264/AVC实现实时编码做出了很大贡献。本文就是对近年来的提出的各种帧内预测模式选择的快速算法的进行了实际验证,并且分析了每种算法的优缺点。     

基于全零模块检测的H.264/AVC快速帧内模式选择算法*

H.264/AVC采用多方向、多划分的帧内预测模式,与其他视频编码标准相比具有更高的编码效率,但同时也使计算复杂度明显提升。通过分析各编码模式的特点和最佳模式分布规律,提出了基于全零模块检测的快速帧内模式选择算法,略过不可能进一步降低率失真代价的帧内预测模式,以降低编码过程的计算复杂度。实验结果表明,在保证编码性能的前提下,可以有效地降低H.264/AVC的计算复杂度。     

H.264/AVC快速帧间模式选择算法研究

H.264/AVC标准采用可变块运动估计和率失真优化技术进行帧间模式选择,提高了编码效率,但极大地增加了计算复杂度。为了解决这一问题,提出一种快速帧间模式选择算法,它利用了SKIP模式在视频序列中的使用率信息和时空域相邻宏块与当前宏块编码模式之间的高度相关性。该算法缩小了模式选择的范围,并采用阈值来提高预测准确度。仿真结果表明,该算法在保持图像质量和比特率的前提下可以大幅度减少计算复杂度。