一种基于HEVC的帧内模式快速判决算法

提出了一种HEVC帧内预测优化快速算法。算法在统计总结出当前CU层与其上层CU帧内预测模式、CBF与TU分割深度、相邻CU层之间的色度帧内预测模式之间相关性的基础上,有效地减少了帧内模式的预测,降低了帧内编码计算复杂度。同时,本文根据不同代价函数之间,以及色度与亮度帧内预测模式之间的相关性,分别在亮度和色度帧内预测过程中添加了RMD中cost代价最小的预测模式和最佳亮度预测模式,保证了较低的编码码率和较高的编码图像质量。实验结果表明,本文算法针对各类型、分辨率的视频,在码率和PSNR基本不变的情况下,帧内编码时间平均减少38.2%。     

基于HEVC的帧内模式快速判决算法

提出了一种HEVC帧内预测优化快速算法。算法在统计总结出当前CU层与其上层CU帧内预测模式、CBF与TU分割深度、相邻CU层之间的色度帧内预测模式之间相关性的基础上,有效地减少了帧内模式的预测,降低了帧内编码计算复杂度。同时,根据不同代价函数之间,以及色度与亮度帧内预测模式之间的相关性,分别在亮度和色度帧内预测过程中添加了RMD中cost代价最小的预测模式和最佳亮度预测模式,保证了较低的编码码率和较高的编码图像质量。实验结果表明,该算法针对各类型、分辨率的视频,在码率和PSNR基本不变的情况下,帧内编码时间平均减少38.2%。     

快速帧内预测模式选择新方法

为了提高编码性能,H.264采用了RDO(率失真优化),但与此同时带来的是计算复杂度的增加.本文着重分析了H.264中快速帧内预测模式选择的问题.为了降低帧内预测模式选择的计算复杂度,提出了一种高效的快速帧内预测模式选择算法.首先,对Pan的基于边缘方向直方图的快速算法进行了改进,同时提出了基于参考象素特征的4×4快速帧内预测模式选择算法,并将两者进行了结合.实验结果表明,本文算法和H.264校验模型JM61相比,I帧编码时间降低61%~69%,而PSNR基本保持不变,输出码率仅略有增加;与Pan的基于边缘方向直方图快速算法相比,本文算法的I帧编码时间降低12%~33%,PSNR和输出码率均基本保持不变.     

利用纹理结构的HEVC快速帧内模式选择算法

高性能视频编码（HEVC）是刚确立的最新一代的视频编码标准。对于帧内编码,HEVC最大的特点是采用了从64×64至8×8的编码单元划分和35种帧内预测模式,HEVC通过遍历所有的分块和帧内预测模式,选取最优的预测方式,这种帧内预测方式在提高预测精度的同时也大大增加了编码的计算复杂度。为了降低帧内预测的计算复杂度,HM2.0版以上的HEVC测试软件采用一种基于两步预测的快速帧内模式选择算法。在此基础上本文首先提出了一种基于纹理方向的快速粗选方案,减少参与计算的粗选模式数,进而提出基于结构相关的决策方法,利用同质图像区域的纹理相似性,减少参与率失真代价函数计算的候选模式数量,进一步降低了帧内预测计算复杂度。实验结果表明,本文所提出的快速算法,在保持编码质量基本不变的条件下,可以使基于两步预测的快速帧内模式选择时间缩短25%。      

HEVC帧内彩色边缘检测快速模式选择算法

高效视频编码(High Efficiency Video Coding,HEVC)相较于H.264/AVC,帧内预测模式有35种,编码性能得到提高的同时也引起了算法复杂度的增加,本文提出了一种基于Canny彩色算子的快速帧内预测模式选择算法。该算法基于图像物理边缘的梯度方向提前分析预测块（Prediction Unites,PU）的方向,预先确定帧内预测的模式,避免算法遍历35种帧内预测模式。实验结果表明,该算法能够有效地降低帧内编码的复杂度,算法编码时间平均减少23.36%而仅损失0.69%的BD-Rate,且率失真性能良好。     

一种低复杂度的HEVC帧内快速编码算法

为了降低高效视频编码(HEVC)帧内编码复杂度,提出一种HEVC帧内快速编码算法。根据视频图像的纹理复杂性,提前跳过或者中止部分尺寸的编码单元(CU)的划分,减少CU深度遍历区间;同时,根据粗选过程后预测模式和代价值的统计特性采用阈值法或者梯度模式直方图法进一步筛选掉粗选后可能性较小的预测模式,从而减少最后进行率失真(RD)代价计算的帧内预测模式数量,进一步降低编码复杂度。实验结果表明,本文算法与HEVC原始平台相比,在全I帧编码模式下编码时间平均减少42.20%,码率(BR)上升约1.75%,峰值信噪比(PSNR)降低了0.108dB,有利于实时应用。     

一种HEVC帧内快速编码算法

高效视频编码(HEVC)采用编码单元(CU)四叉树的 分割结构,相比H.264/AVC显著地提升了编码效 率,但却使编码复杂度急剧增加。为此,本文提出一种帧内快速编码算法。首先,根据视 频图像纹理复 杂度,提前判断是否进行最大编码单元(LCU)分割。然后,根据空域相邻CU的深度预测当前C U的深度范围, 跳过不必要的计算;最后,根据预测模式被选为最优预测模式的统计特性,去掉可能性小的 帧内预测模式。本文算法在HM14.0的基础上实现。 仿真结果表明,本文算法在全I帧模式下与HM14.0相比,帧内编码时 间平均减少38%,码率(BR)只增加1.41%,峰值信噪比(PSNR)只降低0.29dB,在保证编码性能和视频质量几乎不变的 情况下,本文算法降低了编码的计算复杂度。     

一种H.264/AVC帧内预测模式的快速选择算法

H.264/AVC帧内预测技术采用率失真优化策略进行最优化编码模式选择,提高了I帧的编码效率,但同时也提高了计算复杂度。本文提出了一种帧内预测模式的快速选择算法,基于亮度块的方向特性,通过一些复杂度不大的计算,选择少数几个可能性较大的预测模式进行率失真代价计算,得到最佳亮度预测模式,并以 计算代替率失真代价计算选择最佳色度预测模式,降低了计算复杂度,提高了编码速度。实验结果表明,本文提出的算法在保证图像质量的同时,编码时间平均降低了48%,而码率增加很小。     

一种基于时域相关性的高性能视频编码快速帧间预测单元模式判决算法

为了降低高性能视频编码(HEVC)的编码计算复杂度,根据视频时域上高度相关性的特点,该文提出一种快速高性能视频编码(HEVC)帧间预测单元(PU)模式判决算法。分析了时域上相邻帧两帧相同位置编码单元(CU)的PU模式之间的相关性;同时,针对视频中可能存在对象运动,还分析了前一帧对应位置CU的周边CU与当前帧中当前CU间PU模式的相关性。根据分析的时域相关性,跳过当前CU中冗余的PU模式,从而降低编码复杂度。实验结果表明,在编码效率和峰值信噪比(PSNR)损失很小的情况下,在目前已有的HEVC快速帧间预测算法的基础上,进一步降低了31.30%的编码时间。     

x265的低复杂度帧内编码快速算法

为了降低x265的帧内编码复杂度,减少编码所需时间,本文针对新一 代高效视频编码标准(HEVC)帧内编码单元(CU)划分以 及预测单元(PU)模式选择的快速算法进行研究。采用经典的差分矩阵计算纹理复杂度,提出 了一种根据当前编码单元子块的纹理复杂 相似度与其编码所需要的总比特数以及量化参数之间的关系作为提前终止CU划分的判决 条件,通过增加SATD的计算进一 步减少PU模式选择的RDO候选列表的个数从而减少率失真代价计算的快速算法。实验结果 表明,与x265的标准算法相比, 该算法在平均峰值信噪比(PSNR)仅减少0.028dB和码率平均增加1.27%的情况下,能够平均减少32.34%的帧内编 码时间。     

Rough mode cost–based fast intra coding for high-efficiency video coding

The quadtree-based coding unit (CU) and transform unit (TU) structure, as well as various prediction units (PUs) of HEVC, considerably increase encoding complexity in intra coding and inter coding. This paper proposes a rough mode cost (RMC)-based algorithm for accelerating CU/TU depth decisions and PU mode decisions in HEVC intra coding. For CU depth decisions, RMC values are used for the fast determination of CU partition. In the case of PU mode decisions, modes with higher RMCs are removed from the candidate list to reduce the number of test modes. For TU depth decisions, the TU partition of the mode with the least RMC is used to determine the TU partitions of remaining modes. The proposed TU partitioning method demonstrates superior performance to the default method in reference software. The proposed algorithm can reduce encoding time by approximately 51% on average, with a 0.69% increase in the Bjøntegaard-Delta (BD) rate.     

A novel fast intra mode decision for versatile video coding

The latest video coding standard Versatile Video Coding (VVC) obtains superior coding efficiency compared to the High Efficiency Video Coding (HEVC), which is achieved by incorporating more effective and complex new coding tools. In this paper, we propose a novel fast intra mode decision algorithm for VVC, including following two strategies: (1) the correlation between the optimal modes of the adjacent blocks and the modes selected in the rough modes decision (RMD) process is analyzed and applied to reduce the modes in the candidate list; (2) modes in the candidate list are sorted in ascending order according to the modes’ cost calculated in the RMD process. An early termination method is proposed for terminating the optimal prediction mode decision process based on this new order early. These two strategies are incorporated into intra coding to reduce the coding complexity. Since these two strategies do not add any additional computational complexity, the proposed fast algorithm can achieve more complexity reduction. The experimental results show that the complexity reduction of the proposed algorithm is up to 44.74% compared to VVC reference software VTM2.0, and averagely 30.59% encoding time saving with 0.86% BDBR increase.     

A Fast Intra‐Prediction Method in HEVC Using Rate‐Distortion Estimation Based on Hadamard Transform

A fast intra‐prediction method is proposed for High Efficiency Video Coding (HEVC) using a fast intra‐mode decision and fast coding unit (CU) size decision. HEVC supports very sophisticated intra modes and a recursive quadtree‐based CU structure. To provide a high coding efficiency, the mode and CU size are selected in a rate‐distortion optimized manner. This causes a high computational complexity in the encoder, and, for practical applications, the complexity should be significantly reduced. In this paper, among the many predefined modes, the intra‐prediction mode is chosen without rate‐distortion optimization processes, instead using the difference between the minimum and second minimum of the rate‐distortion cost estimation based on the Hadamard transform. The experiment results show that the proposed method achieves a 49.04% reduction in the intra‐prediction time and a 32.74% reduction in the total encoding time with a nearly similar coding performance to that of HEVC test model 2.1.     

CU encoding depth prediction,early CU splitting termination and fast mode decision for fast HEVC intra-coding

High Efficiency Video Coding (HEVC) is a new video coding standard achieving about a 50% bit rate reduction compared to the popular H.264/AVC High Profile with the same subjective reproduced video quality. Better coding efficiency is attained, however, at the cost of significantly increased encoding complexity. Therefore, fast encoding algorithms with little loss in coding efficiency is necessary for HEVC to be successfully adopted for real applications. In this paper we propose a fast encoding technique applicable to HEVC all intra encoding. The proposed fast encoding technique consists of coding unit (CU) search depth prediction, early CU splitting termination, and fast mode decision. In CU search depth prediction, the depth of encoded CU in the current coding tree unit (CTU) is limited to predicted range, which is mostly narrower than the full depth range. Early CU splitting skips mode search of its sub-CUs when rate distortion (RD) cost of current CU is below the estimated RD cost at the current CU depth. RD cost and encoded CU depth distribution of the collocated CTU of the previous frame are utilized both to predict the encoding CU depth search range and to estimate the RD cost for CU splitting termination. Fast mode decision reduces the number of candidate modes for full rate distortion optimized quantization on the basis of the low complexity costs computed in the preceding rough mode decision step. When all these three methods are applied, proposed fast HEVC intra encoding technique reduces the encoding time of the reference encoder by 57% on the average, with only 0.6% of coding efficiency loss in terms of Bjontegaard delta (BD) rate increase under the HEVC common test conditions.     

Piecewise DC prediction in HEVC

In this paper, we propose an improved DC prediction method for high-efficiency video coding (HEVC) intra coding. The technique involves the application of pixel-wise predictors rather than block-based predictor in the DC mode. In HEVC, the pixels of neighboring reconstructed blocks are used to support multiple directional spatial prediction modes and reduce spatial redundancy. For lossless coding, pixel-by-pixel differential pulse code modulation (DPCM) is applied to directional predictions. Consequently, residuals are reduced and coding efficiency is improved. Since DC prediction still employs block-based coding, pixel-wise DC prediction is needed for better coding efficiency. When compared to HEVC lossless intra coding, the proposed algorithm reduces the bit rate by 5.95%. Furthermore, with pixel-by-pixel DPCM, the average bit rate reduction is 10.64% when compared to HEVC lossless intra coding.     

基于纹理方向和空域相关的HEVC帧内快速编码算法

为了降低高效视频编码(HEVC)的复杂度,提出了一种基于纹理方向和空域相关性的帧内快速编码算法。一方面,利用相邻编码单元(CU,coding unit)的最佳分割尺寸确定相关性的权重,并根据已编码CU的率失真代价值定义了CU分割尺寸的相关性因子,通过比较该因子提前终止CU分割;另一方面,利用Sobel算子求取预测单元(PU,prediction unit)子块的纹理方向,通过判定其纹理方向显著性确定相应的候选模式集,然后根据PU大小对所得的预测模式修正处理,最后遍历这些候选模式选取最优模式。实验结果表明:本文算法相对于原始HEVC编码方法,在全I帧模式下编码时间平均减少36.84%,BDBR(Bjntegaard delta bit rate)上升约0.81%,BDPSNR(Bjntegaard delta peak signal-to-noise rate)降低了0.047dB。     

Fast prediction unit selection method for HEVC intra prediction based on salient regions

In order to reduce the computational complexity of the high efficiency video coding(HEVC) standard, a new algorithm for HEVC intra prediction, namely, fast prediction unit(PU) size selection method for HEVC based on salient regions is proposed in this paper. We first build a saliency map for each largest coding unit(LCU) to reduce its texture complexity. Secondly, the optimal PU size is determined via a scheme that implements an information entropy comparison among sub-blocks of saliency maps. Finally, we apply the partitioning result of saliency map on the original LCUs, obtaining the optimal partitioning result. Our algorithm can determine the PU size in advance to the angular prediction in intra coding, reducing computational complexity of HEVC. The experimental results show that our algorithm achieves a 37.9% reduction in encoding time, while producing a negligible loss in Bjontegaard delta bit rate(BDBR) of 0.62%.