基于感知的多视点视频编码宏块模式选择快速算法

多视点视频编码(MVC)采取可变块模式选择技术和 多参考帧技术显著提高了编码的压缩效率,但同时带来了巨大的 编码计算复杂度。为了降低MVC的计算复杂度,提出基于感知的快速MVC宏块模式选择 算法。基于人眼视觉感知的特点,利用视觉恰可察觉失真(JND)的概念建立MVC宏块的最优模 式和JND的联系,并利用该联系确定早期结束最优宏块模式选择过程的阈值,根据当前编码 宏块的JND与阈值的 关系自适应地减少每个编码宏块的模式搜索次数,进而减少MVC的方向搜索和参考帧搜索的 次数,以降 低编码的复杂度,提高MVC速度。实验结果显示,对于不同运动特性、内容、纹理信息、相 机间距和图像 尺寸的测试序列,提出的快速算法在率失真性能几乎不变的情况下平均节约76.00% 编码时间。     

基于相邻宏块率失真代价的JMVC快速算法

为了降低JMVC(Joint Multiview Video Coding联合多视点视频编码)编码复杂度,提出一种根据前一编码宏块参考方向和率失真代价,提前终止JMVC模式选择的算法。该算法首先获取前一宏块的率失真代价和参考方向,随后根据前一宏块参考方向为当前宏块的搜索设定一个率失真代价门限,最后利用此门限实现提前终止。实验结果显示,相比于JMVC原始算法,本文算法的编码质量没有下降,而编码时间节省了34.86%~54.23%。算法可以在保证编码质量的前提下,有效地较低编码复杂度。     

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.     

采用率失真与模式特征的多视点视频编码快速模式选择

现有的多视点视频编码使用了分层B帧（Hierarchical B Picture, HBP）的预测结构,其帧内预测、帧间预测以及视点间预测的模式选择给多视点视频编码带来了庞大的计算复杂度。针对这一问题,我们在分析了JMVC模式分布比例的基础上,提出了一个快速帧间模式选择的算法。这种算法利用率失真代价和预测模式特征之间的关系来及时判定最优模式:如果上一尺寸预测模式的率失真代价小于当前尺寸预测模式的率失真代价则认为上一预测模式为最优模式,跳过检查其他更小尺寸的预测模式;反之,如果上一尺寸的预测模式的率失真代价大于当前尺寸的预测模式的率失真代价,则继续检查其他更小的尺寸。这样,通过提前终止一些不必要的模式选择过程,多视点视频编码的计算量得到大幅的降低。实验结果表明:所提算法能在保持JMVC中全搜索算法的编码效率同时,使计算复杂度减少了81.66%。      

基于转移概率的多视点视频快速模式选择算法

针对多视点视频编码(MVC)中部分大宏块模式(SKI P/DIRECT模式,帧间16×16模式)相对于其它模式的计算复杂 度低,并且在编码所确定的最优模式中占有相当高比重的特点,本文提出一种基于转移概率 的多视点视频 快速模式选择算法。首先根据多视点视频当前编码宏块对应时间和视点间宏块及周围宏块的 位置几何关系, 建立宏块模式参考模型;其次比较参考模型中模式的时间相似度和视点间相似度;最后计算 模式之间的转 移概率,确定提前结束大宏块模式选择过程的阈值。实验结果表明,本文所提出的快速算法 平均节约MVC时间80.93%,编码质量平均下降0.04dB,码率平均增加0.27%。     

H.264快速自适应帧间编码模式选择算法

提出了一种针对H．264标准的帧间编码模式快速自适应选择算法用以减少编码器的复杂度。该算法利用运动补偿后残差宏块的统计信息．将需要计算率失真代价函数的候选模式减少为一个模式组中包含的模式子集。由于该算法采用了重叠划分的模式组以及动态调整的门限．可以最大可能保证宏块的最佳编码模式处于所选择的模式组中，所以可以在编码质量下降很小的情况下，大幅度降低编码复杂度。实验表明，本算法平均可以节省编码时间52％．同时PSNR下降约为-0．05dB,不会影响主观视觉效果。     

基于空间相关性的H.264快速自适应模式选择算法

为了减小H.264编码器的复杂度,提出了一种帧间预测模式快速自适应选择算法。该算法首先利用运动补偿后残差宏块的统计信息,将需要计算率失真代价函数的候选模式减少为一个模式组中包含的模式子集;然后根据相邻的左块和上块的模式,从所选择的模式子集中选出出现概率最高的两种模式来计算并比较率失真代价函数,选出代价最小的模式作为最佳模式。实验表明,本算法平均可以节省编码时间约65%,同时PSNR下降约为?0.24dB,有利于实时应用。     

应用模糊隶属度的H.264帧内预测模式快速选择

H.264中采用的率失真优化技术虽然提高了编码效率,但也使计算复杂度增加,影响编码的实时实现。针对这一问题,通过分析H.264中计算复杂度较高的帧内预测模式选择部分,提出一种新的帧内预测模式选择算法。根据模糊隶属度函数预先判断宏块类型,从Intra_4×4和Intra_16×16两种预测模式中选择一种,并通过判断4×4块的纹理方向,减少候选预测模式的数量。实验结果表明,在保持图像性能和码率基本不变的情况下,该算法能有效提高H.264的编码速度,有利于实时应用。     

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。      

H.264宏块模式的一种快速判决方案

H.264采用了可变块运动估计和率失真优化模式判决,极大地增加了编码器的复杂度.本文利用H.264参考软件对时间/空间相邻宏块模式之间的相关性进行了分析,相应地提出了一种快速算法以降低模式判决的运算复杂度.利用已编码相邻宏块的运动信息和模式类型比率信息预测当前宏块的候选模式类型,然后采用部分率失真优化决定当前宏块的编码模式.如果某些模式不在候选模式之列,就不再对其做运动估计.如果相邻宏块的平均失真超过了预定阈值,当前宏块就采用常规的率失真优化模式判决.实验结果表明,对于A、B类测试图像序列,采用本文方案可以明显降低编码复杂度,而编码质量只有轻微的下降.     

Fast macroblock encoding algorithm based on rate-distortion activity for multiview video coding

Multiview video coding (MVC) is the appendix H of H.264/AVC, and it requires a great amount of time to compress multiple viewpoints׳ video with complex prediction structures. To reduce the whole computational complexity of MVC, this paper proposes a fast macroblock (MB) encoding algorithm based on rate-distortion (RD) activity, and it includes the fast mode decision and the fast motion/disparity estimation. First, the RD activity type of the current MB is calculated by utilizing the Skip/Direct RD cost and the average RD costs of classified MB modes. Then, through utilizing the RD activity type and RD costs of the estimated modes, the selection of candidate modes, the early decision of Skip/Direct mode, and the reduction of Inter8×8 mode estimation are all presented in the fast mode decision. By using the RD activity type and the correlations of vectors, the selection of search center and the prediction of search range are introduced in the fast motion/disparity estimation. In addition, the proposed algorithm can be applied to temporal and inter-view views as well as anchor and non-anchor frames. An experiment with a wide range of video scenes, camera setups and quantization parameters was implemented, and the results confirmed that the proposed algorithm can reduce the encoding time significantly while maintaining a similar RD performance as the original MVC encoder. Compared to the state-of-the-art algorithms, the proposed algorithm also demonstrated better performances in the various test cases.     

Efficient intra-mode skip algorithm using RD costs of SUB8 3 8 and I4MB

H.264/AVC employs a rate-distortion (RD) optimisation technique to determine the best coding mode for each macroblock (MB). An intra-mode skip decision algorithm is presented based on RD costs of the SUB8 times 8 mode and the 14 MB mode to reduce the processing time. Experimental results on test video sequences show that the computational complexity has been reduced by about 20%, with nearly negligible loss of peak signal-to-noise ratio (PSNR) value.     

Efficient multi-view video coding using inter-view information

Multi-view video coding (MVC) has been extended from H.264/AVC to improve the coding efficiency of multi-view video. This paper proposes a fast mode decision algorithm which can make an early decision on the correct mode partition to solve the issue of the enormous computational complexity. The best modes of the reference views are utilized to determine the complexity of the macroblock (MB) in the current view, the mode candidates needed to be calculated can then be obtained according to the complexity. If the complexity is low or medium, the search range can be reduced. The threshold of the rate-distortion cost for the current MB is calculated using the co-located and neighboring MBs in previously coded view and is utilized as the criterion for early termination. The motion vector difference in the reference view is applied to dynamically adjust the search range in the current MB. Experimental results prove that the proposed algorithm achieves a time saving of 81.05% for a fast TZ search and 87.85% for full search, and still maintains quality performance and bitrate.     

Coding statistics based fast mode decision for multi-view video coding

Reduction of high computational complexity of multi-view video coding (MVC) is necessary for realization in consumer electronics. Since mode decision is one of the key computational bottlenecks of multi-view video encoders, this paper proposes a coding statistics based fast mode decision algorithm. First of all, a rate–distortion cost based fast DIRECT mode decision algorithm early terminates the mode decision process if possible. Next, the candidates for Inter modes are reduced by taking the advantage of the correlation between an optimal mode and motion cost. The proper thresholds to reduce the candidates for the above two fast algorithms can be easily derived from exponential functions at run time. Finally, motion vector difference based motion characteristics is referred to further speed up the mode decision process of Inter modes. The experimental results show that the proposed scheme reduces up to 70.82% of encoding time with negligible degradation of RD performance.     

Efficient early direct mode decision for multi-view video coding

Multi-view video coding (MVC) uses various prediction modes and exhaustive mode decision to achieve high coding efficiency. However, the introduced heavy computational complexity becomes the bottleneck of the practical application of MVC. For this, an efficient early Direct mode decision for MVC is proposed in this paper. Based on the observation that the Direct mode is highly possible to be the optimal mode, the proposed method first computes the rate distortion (RD) cost of the Direct mode and compares this RD cost value with an adaptive threshold for providing an early termination chance as follows. If this RD cost value is smaller than the adaptive threshold, the Direct mode will be selected as the optimal mode and the checking process of the remaining modes will be skipped; otherwise, all the modes will be checked to select the one with the minimum RD cost as the optimal mode. Note that the above-mentioned adaptive threshold is determined as the median prediction value of a set of thresholds, which are derived by using the spatial, temporal and inter-view correlations between the current macroblock (MB) and its neighboring MBs, respectively. Experimental results have demonstrated that the proposed method is able to significantly reduce the computational complexity of MVC with negligible loss of coding efficiency, compared with the exhaustive mode decision in MVC.     

A Fast Intra Skip Detection Algorithm for H.264/AVC Video Encoding

A fast intra skip detection algorithm based on the rate‐distortion (RD) cost for an inter frame (P‐slices) is proposed for H.264/AVC video encoding. In the H.264/AVC coding standard, a robust rate‐distortion optimization technique is used to select the best coding mode and reference frame for each macroblock (MB). There are three types of intra predictions according to profiles. These are 16×16 and 4×4 intra predictions for luminance and an 8×8 intra prediction for chroma. For the high profile, an 8×8 intra prediction has been added for luminance. The 4×4 prediction mode has 9 prediction directions with 4 directions for 16×16 and 8×8 luma, and 8×8 chrominance. In addition to the inter mode search procedure, an intra mode search causes a significant increase in the complexity and computational load for an inter frame. To reduce the computational load of the intra mode search at the inter frame, the RD costs of the neighborhood MBs for the current MB are used and we propose an adaptive thresholding scheme for the intra skip extraction. We verified the performance of the proposed scheme through comparative analysis of experimental results using joint model reference software. The overall encoding time was reduced up to 32% for the IPPP sequence type and 35% for the IBBPBBP sequence type.     

H.264的帧间宏块模式选择算法

H.264中定义了7种不同大小的帧间宏块模式,为了提高编码效率,编码时对每一种宏块模式都进行运动搜索,并利用率失真优化(RDO)分别计算编码代价,选择编码代价最小的模式作为帧间编码模式,但是计算量非常大,导致运动估计速度缓慢,很难实现实时编码。本文提出一种选择宏块模式的快速算法,通过宏块模式编码代价的比较,提前确定宏块模式,从而逐步减少不必要的宏块搜索和RDO计算。实验结果表明,此方法与全宏块模式搜索相比较,图像质量和码流只有少量变化,而编码速度有显著提高。     

基于深度图像的H.264快速帧间模式选择算法

H.264编码标准的帧间模式选择算法采用全候选模式搜寻算法,为编码器带来了高运算复杂度。提出一种快速帧间模式选择算法,旨在降低H.264帧间编码的运算复杂度。算法利用深度图像信息从彩色图像中分割出背景区域和运动剧烈的区域,宏块根据所在的区域选择相应的编码策略,从而达到缩小候选模式范围,加快模式选择速度的目的。实验证明,该算法在图像质量基本不变的情况下编码时间平均节省23%以上。     

多视点编码中一种快速的模式选择方法

在多视点视频编码中,多尺寸的运动估计和视点估计被用来选择宏块的最优编码模式。这些技术大大提高了编码效率,但是却带来了庞大的计算复杂度,从而影响了多视点视频编码的广泛应用。提出了一种新的模式选择的快速算法,利用了相邻视点的模式相关性来减少执行不需要的模式。实验表明,所提出的快速模式选择算法在不降低编码效率的同时可以显著降低计算复杂度。