基于梯度方向算子的H.264帧内模式选择算法

提出梯度方向算子的概念,基于该算子提出了一种H.264帧内模式快速选择算法。本文首先应用梯度方向算子计算编码宏块中各4×4亮度子块的纹理特征和灰度起伏特征,根据这两种特征参量削减4×4帧内候选预测模式。通过统计宏块中各子块的4×4候选预测模式信息,结合梯度方向强度门限判别法削减宏块的16×16候选预测模式,通过率失真优化算法计算得到最优亮度预测模式。进一步根据亮度宏块和色度宏块的对应关系,在亮度候选预测模式的基础上对色度宏块候选预测模式进行削减,最后计算得到最优色度预测模式。该算法削减了50%以上的帧内预测模式,减少了帧内预测模式选择的运算量,实验表明,该算法能够在峰值信噪比和码流比特率变化轻微的前提下减少50%以上的运算量。      

Mode dependent loop filter for intra prediction coding in H.264/AVC

In this paper, a high performance and low complexity loop filter is proposed for intra prediction coding. Although the deblocking loop filter (DLF) has achieved outstanding performance on suppressing quantization noise, it also induces details information loss because of the smoothing operation. To achieve better restoration performance, we propose a filter set named mode dependent loop filter (MDLF) which adaptively select the filter coefficients according to various local characteristics. In the homogeneous areas, the task of the filter emphasizes on smoothing the noise. In the heterogeneous areas, the proposed filter concentrates on preserving the details. Based on the spatial correlation assumption and statistical analysis, the intra mode combination is used to classify the training samples with different local characteristics. Then the classical least mean square error framework is employed to solve the coefficients for the proposed filter set. In this way, a more efficient adaptive loop filter scheme can be achieved for specific intra mode combination. Experiment results show that the proposed loop filter achieves superior coding gains compared to the H.264/AVC High Profile. Furthermore, relative to QALF+DLF, a comparable performance also can be achieved by the proposed MDLF with far less complexity increase.     

H.264帧内预测模式快速判定算法研究

帧内预测作为H.264中提高编码效率的重要部分,其采用了率失真优化技术（RDO）进行预测模式的选择,但同时编码复杂度和计算量也明显增加.为此,提出一种快速判定算法.该算法利用区域图像的质心坐标对区域图像的平坦性和方向性进行判断,算法通过判断宏块的平坦性提前选定块大小,根据4×4块的纹理方向,确定预测模式集,降低算法复杂度.实验结果表明,与H.264标准参考编解码器JM8.6相比,所提算法编码时间节省50％以上,峰值信噪比和码率变化不大.     

An improved fast mode decision algorithm for intraprediction in H.264/AVC video coding

In this article, an improved version of one of the most cited intra mode decision algorithms in H.264/AVC video coding is proposed with the aim to improve its efficiency and performance. The reference algorithm determines the interpolation/extrapolation spatial direction (mode) for achieving the best intra prediction using the Sobel gradient calculation. The proposed algorithm suggests reducing the number of gradients calculated and changing the Sobel operator to that of Roberts. In addition to this, it also proposes including the previously encoded neighboring block modes among the evaluated modes. Experimental results show that the proposed algorithm reduces the computational load of the original algorithm and substantially improves its rate-distortion performance.     

Modification and implementation of an edge-based fast intra prediction mode decision algorithm for H.264/AVC high resolution real-time systems

In this paper, we propose an architecture for H.264/AVC fast intra-prediction-mode decision making in high resolution real-time applications. Intra-prediction-mode decision making requires many computations of H.264/AVC video coding, and also extra time for mode generation for intra prediction mode decisions. Hence, there exists a bottleneck in the execution of high resolution real-time applications. To improve the operation of intra prediction mode decision, we use an algorithm which, based on the edge information of an object, will reduce estimations of mode predictions by 66%; with negligible loss of video quality and a small increase in bit-rate of video stream. We propose a low cost architecture, with gate counts reduced by 50% compared with former design. The total gate count is 86,671 and the maximum operating frequency is 250 MHz using TSMC 0.18 μm cell-based technology. The experimental results show our design is a strong competitor with most modern high resolution, real-time video processing.     

一种基于H.264/AVC帧内预测模式选择的快速算法

依据宏块的空间相关性,并从概率的角度考虑,提出了一种新的快速模式选择算法,该方法减少了对Intra4×4和Intra16×16的预测模式率失真的计算,降低了帧内预测编码的复杂度.与参考软件JM11.0中模式选择算法相比,在PSNR基本保持不变的情况下,新算法的编码时间缩短了大约30%,而比特率仅提高了1%左右.     

Adaptive Scanning for H.264/AVC Intra Coding

In this letter, an adaptive scanning that improves intra coding efficiency in the H.264/AVC standard is proposed. The proposed adaptive scanning utilizes the prediction directions (modes) that include the horizontal and vertical edge information in a block. Depending on the prediction directions, the proposed method uses three scanning methods: zigzag scanning, horizontal scanning, and vertical scanning. In the proposed method, horizontal and vertical scanning are used in vertical and horizontal prediction modes, respectively, and the normal zigzag scanning in the H.264 standard is used in all other intra prediction modes. The proposed method reduces the bit rate by approximately 2.5% compared with H.264/AVC, without the degradation of video quality.     

Parallel fast inter mode decision for H.264/AVC encoding

For H.264/AVC encoding, the mode selection process consumes a large proportion of the overall computation. To reduce this burden, various fast mode decision algorithms have been proposed. The current fast mode decision algorithms usually exploit the relationship among the coding modes and use the context-based approach to reduce the number of modes to be checked for both intra coding and inter coding. The parallel capacity of hardware architectures are also taken into consideration. However, almost all the parallel fast mode decision designs are focusing on intra coding. In this paper, a hardware friendly parallel fast inter mode decision method is proposed. With the proposed method, the inter mode decision can be conducted efficiently in one pass and significant encoding speedup can be achieved with negligible coding efficiency loss. Moreover, the proposed method can be easily mapped to hardware architecture which can be used for the real-time video encoding.     

H.264/AVC帧内预测模式选择的快速算法研究

H.264/AVC标准引入RDO技术计算帧内预测最优模式,提高编码效率,但同时RDO技术的引入极大提升编码端的计算复杂度.提出了一种针对帧内预测4×4亮度块的快速模式选择算法,该算法利用亮度块SATD值与RDO技术间的相关性,优化原有算法.实验结果表明,算法能在基本不影响图像原有质量的情况下,较大程度减少编码H.264序列所需时间.     

Transparent encryption techniques for H.264/AVC and H.264/SVC compressed video

Transparent encryption of video content requires to provide a video preview that is left in plaintext, while the enhancement information is encrypted. In this paper we propose three algorithms that provide transparent encryption. The first two ones are based on the idea of generating controlled drift in such a way as to obtain the desired quality level, while the third algorithm employs scalable video coding. We provide experimental results on several video sequences, as well as a security analysis, showing that the proposed algorithms provide an effective framework to perform transparent encryption.     

H.264/AVC中并行通用变换结构设计

提出了一种用于H.264/AVC编解码器的通用并行变换结构,并利用Verilog语言进行了电路设计.该并行结构主要包含4个移位器和16个累加器,可以完成H.264/AVC中的全部4×4变换,包括4×4哈达马变换和4×4离散余弦变换和反变换,能够达到每个时钟周期处理一个像素点的速度.使用SMIC 0.18 μm工艺对该并行结构进行了综合,电路面积为3757门,工作在100 MHz时钟频率下的关键路径为10.3 ms.     

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H.264/AVC新技术及其优化

本文详细介绍了视频编码新标准H.264/AVC中的运动估计和运动补偿、预测、证书变换、量化、熵编码环路滤波、帧切换等技术及其优化设计.     

H.264/AVC视频编码标准的技术特点及应用分析

H.264／AVC是ITU-T视频编码专家组和ISO／IEC运动图像专家组(MPEG)共同开发出来的最新视频编码标准,它具备许多新的技术特点,如:多模式运动预测、柔性宏块排序、整数变换、一致性变字长编码、内容自适应二进制算术编码、分层编码、错误约束机制、错误掩盖技术及高效的比特流切换技术等等。本文在阐述该标准系统层结构的基础上,分析其主要技术特点及H.264／AVC VBR码流特性,阐述该标准在IP网络及无线网络中的应用情况。     

A real-time dual watermarking algorithm of H.264/AVC video stream for Video-on-Demand service

A real-time dual watermarking algorithm of H.264/AVC compressed video is proposed for Video-on-Demand (VOD) service. The copyright information and user information are modulated by CDMA spreading strategies as watermark. At the encoder side, copyright information is embedded into the first non-zero coefficient of Intra 4 × 4 coded blocks in the luminance components of I frames. An effective error compensation mechanism is simultaneously introduced into the embedding process, which strictly restricts the distortion caused by quantization and watermark embedding within a step size of quantization. At the server side, a XOR based mapping rule is utilized for watermark embedding because the number of non-zero coefficients after quantization is quite less in P frames. Every two bits of the private user information is mapped to three non-zero coefficients of P frames. Experimental results on test sequences demonstrate that the proposed approach has just slight influence on bit rate and PSNR with real-time performance for VOD services, and achieves the dual purposes of copyright protection and pirate tracking.     

一种基于H.264/AVC的帧间模式快速判决算法

新的视频编码标准H.264/AVC能够获得较高的编码效率是以增加运算复杂度为代价的,1个帧间宏块(MB)的可选编码模式包括7种块尺寸的帧间预测模式和2种块尺寸的帧内预测模式,其校验模型仅给出一种复杂的全搜索方法来确定最佳模式。本文提出一种快速模式判决算法,将全部模式进行分类,通过判别MB的一致性和比较MB的空时相关性逐类型比较,可有效减少判决的模式数量。实验结果表明,这种方法能够在保持视频质量的同时,节省约35%的编码时间。     

H.264/AVC中的SP/SI帧技术

SP/SI帧是最新的视频压缩标准ITU-T H.264(也称ISO/IEC MPEG-4/Part 10-AVC)中定义的两种新类型帧.探讨了SP帧技术的主要特性,即使使用不同的预测参考帧也能解码恢复出相同的SP帧;介绍了一般与SP帧联合使用的SI帧技术;分析了SP帧在流间切换、拼接和随机接入等应用中取代I帧的原理.通过仿真结果表明,在提供相同功能时SP帧的编码效率远远高于I帧.     

H.264/AVC中快速1/4像素运动估计算法

提出了一种快速1/4像素的运动估计算法.该算法基于运动补偿预测误差模型,与传统的1/4像素的分层运动估计算法不同,仅通过一步计算就能直接得到1/4像素精度的运动矢量,而且完全避免了运算量很大的分数像素内插运算和整像素搜索完成后的分数像素搜索.实验结果表明,该算法在保持图像质量的前提下极大地减少了1/4像素运动估计的运算量.     

A Multi-core Architecture Based Parallel Framework for H.264/AVC Deblocking Filters

Deblocking filter is one of the most time consuming modules in the H.264/AVC decoder as indicated in many studies. Therefore, accelerating deblocking filter is critical for improving the overall decoding performance. This paper proposes a novel parallel algorithm for H.264/AVC deblocking filter to speed the H.264/AVC decoder up. We exploit pixel-level data parallelism among filtering steps, and observe that results of each filtering step only affect a limited region of pixels. We call this “the limited propagation effect”. Based on this observation, the proposed algorithm could partition a frame into multiple independent rectangles with arbitrary granularity. The proposed parallel deblocking filter algorithm requires very little synchronization overhead, and provides good scalability. Experimental results show that applying the proposed parallelization method to a SIMD optimized sequential deblocking filter achieves up to 95.31% and 224.07% speedup on a two-core and four-core processor, respectively. We have also observed a significant speedup for H.264/AVC decoding, 21% and 34% on a two-core and four-core processor, respectively.

H．264／AVC率失真优化（RDO）策略研究

本文对H.264/AVC中所运用的率失真优化策略进行了深入研究。首先介绍了率失真理论及率失真优化模型,然后参照JM 8.4代码详细分析了H.264/AVC各模块的代价函数,并重点研究了其编码过程中率失真代价函数的运用策略。最后通过对JM 8.4代码的测试,得出率失真优化的性能,并对其优缺点进行了分析,提出进一步改进和优化的方向。