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.     

基于H.264帧内预测模式的信息隐藏算法

根据H.264标准编码的特点,提出一种较高性能的信息隐藏方案。文章分析H.264中I4×4亮度块的9种帧内预测模式,以及最优模式的选择策略,将I4×4亮度块的9种帧内预测模式作为备选宿主,利用信息嵌入算法将信息嵌入到视频中。这样降低了信息隐藏过程中预测模式调整对视频质量的影响,并能提高嵌入信息数据量。     

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.     

一种低比特率增长的H.264视频信息隐藏算法

提出一种基于预测模式调制的H.264视频信息隐藏算法。在H.264视频的帧内预测过程,通过调制I帧4×4亮度块的帧内预测模式实现隐秘信息的嵌入。调制方法是基于宿主4×4亮度块的边缘强度(DES)划分的映射规则进行的,从而避免了信息隐藏后视频流的比特率的过快增长。同时,通过结合矩阵编码技术使得修改一个预测模式可以隐藏4bit信息。在信息提取过程中,不需要对含密视频进行完全解码,只需获取含密视频的帧内预测模式即能提取秘密信息。实验结果表明,本文算法在提高隐藏容量和保证视频质量的同时,也有效避免了比特率的过快增长。     

一种新的H.264/AVC帧内编码快速算法

针对H.264/AVC帧内编码算法采用率失真优化(RDO)算法提升编码性能导致运算复杂度增加这一问题,提出了一种新的帧内编码快速算法。该算法采用待预测块的纹理方向误差值判断待编码块的纹理特征,结合相邻块的预测模式相关性减少须遍历预测模式的数量,并结合全零块检测的提前终止判定准则加快编码速度。实验结果表明,与标准算法相比,该算法在保证输出码率和图像质量基本不变的情况下能够将帧内编码时间减少约67.2%,显著提高了H.264的帧内编码效率。     

基于多分类的QDCT域大容量H.264/AVC视频信息隐藏算法

提出了一种在开环外的量化离散余弦变换(QDCT )系数上的H.264视频信息隐藏算法。在抑制漂移失真的条件下,对 邻块所需参考像素进行多组分类。其次,充分挖掘帧 内4×4亮度可用QDCT系数对,结合9进制方向调整(EMD)嵌入算法和 矩阵编码,实 现秘密信息的高容量嵌入。同时,通过最多修改一组QDCT系数保证了含密视频的质量。 此外,本文的信息提取算法不需要对含密视频完全解码,只需得到QDCT系数和帧内预测 模式,即可完全提取秘密信息。实验结果表明,本文算法在大幅度提高嵌入容量的同时,对 比特率和视频的质量影响不大。     

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。      

适于航空面阵CCD相机的H.264编码帧内预测算法

为了提高H.264中帧内预测压缩编码效率,提出一种适于航空面阵CCD相机应用的H.264的新的帧内预测模式。其基本思想为:一个块中的每个像素预测值使用周围像素和权重采用一个N阶线性预测器计算得到,而权重值是由重构像素中与待编码像素的邻近块计算得到,可参考的邻近块使用l1范数评估。而权重值并不需要传输到解码器中而耗用大量时间。在H.264参考软件JM17.6上的实验结果表明,本文提出的帧内预测算法具有很好的率失真(RD)性能,与标准H.264帧内预测算法比较,对于图像而言,PSNR增加了0.57~0.17dB,比特率减少了9.71~3.94%;对于CIF格式视频序列,PSNR增加了0.05~0.14dB,比特率减少了1.23~1.52%;对于720p50格式视频序列,PSNR增加了0.01~0.05dB,比特率减少了0.25~0.47%。因此,本文算法非常适于航空面阵CCD相机的应用。     

基于H.264/AVC的视频信息隐藏算法

在H.264/AVC的帧内预测环节,调制H.264/AVC编码中I帧4×4亮度块的帧内预测模式实现信息隐藏.这种调制基于该模式与待隐藏比特之间的映射规则进行.宿主4×4块的具体位置由各块自身特点结合密钥所指定的嵌入位置模板确定.信息的提取过程不需要原始视频内容,也不需完全解码,而只要对码流中的帧内预测模式进行解码即可.     

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.     

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.     

Enhanced Inter Mode Decision Based on Contextual Prediction for P‐Slices in H.264/AVC Video Coding

We propose a fast macroblock mode prediction and decision algorithm based on contextual information for P‐slices in the H.264/AVC video standard, in which the mode prediction part is composed of intra and inter modes. There are nine 4×4 and four 16×16 modes in the intra mode prediction, and seven block types exist for the best coding gain based on rate‐distortion optimization. This scheme gives rise to exhaustive computations (search) in the coding procedure. To overcome this problem, a fast inter mode prediction scheme is applied that uses contextual mode information for P‐slices. We verify the performance of the proposed scheme through a comparative analysis of experimental results. The suggested mode search procedure increased more than 57% in speed compared to a full mode search and more than 20% compared to the other methods.     

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。     

HEVC帧内预测模式和分组码的视频信息隐藏

为了在最新的视频压缩标准－高效视频编码(HEVC) 下实现信息隐藏并在保证隐秘信息嵌入容量的前提下减少对宿 主信息的修改,提出基于帧内预测模式和分组码的HEVC视频信息隐藏方法。首先,利用分组 码的标准阵 列译码方法,建立(4,3)码标准阵列译表;然后,根据译码表与预测模式的映射关系,调 制帧内4×4亮 度块的预测模式嵌入隐秘信息;最后,对调制后的4×4亮度块重新编码,使得在连续4个4× 4帧内亮度 块嵌入3bit隐秘信息,平均修改1.25位预测模式,减小因调制预测模式对视频造成的影响 。实验结果表 明:所提算法的PSNR值下降在0.05 dB以内,码率增长在1%左右 ,算法能很好的保证视频主客观质量,对视频的编码比特率影响很小。     

Gravity direction-based ultra-fast intraprediction algorithm for H.264/AVC video coding

The H.264/AVC video coding standard uses in intraprediction, 9 directional modes for 4 × 4 and 8 × 8 luma blocks, and 4 directional modes for 16 × 16 luma macroblocks, and 8 × 8 chroma blocks. The use of the variable block size and multiple modes in intraprediction makes the intracoding of H.264/AVC very efficient compared with other compression standards; however, computational complexity is increased significantly. In this paper, we propose a fast mode selection algorithm for intracoding. This algorithm is based on the vector of the block’s gravity center whose direction is used to select the best candidate prediction mode for intracoding. On this basis, only a small number of intraprediction modes are chosen for rate distortion optimization (RDO) calculation. Different video sequences are used to test the performance of proposed method. The simulation results show that the proposed algorithm increases significantly the speed of intracoding with negligible loss of peak signal-to-noise ratio quality.     

改进的H.264快速帧内预测选择算法

新一代的视频压缩标准H.264在视频数据压缩技术上取得了重大进展,但其算法复杂度明显提升,编码时间也较长。为降低H.264的计算复杂度和提高压缩效率,本文提出了一种基于变换域特性的变换域立体型（TDST）帧内预测快速选择算法,通过哈德码（Hadamard）变换的变换域特性对预测模式先进行选择,过滤掉大部分的预选模式,利...     

Enhanced SATD-based cost function for mode selection of H.264/AVC intra coding

In H.264/AVC, the concept of rate-distortion optimization (RDO) mode decision has proven to be an important coding tool. However, this mode decision method makes the encoding process extremely complex, especially in the computation of the rate-distortion cost function, which includes the computations of the sum of squared difference (SSD) between the original and reconstructed image blocks and context-based entropy coding of the block. In this paper, we propose an enhanced low-complexity cost function for H.264/AVC intra 4 × 4 and 8 × 8 mode selections. The enhanced cost function uses sum of absolute Hadamard-transformed differences (SATD) and mean absolute deviation of the residual block to estimate distortion part of the cost function. A threshold-based large coefficients count is also used for estimating the bit-rate part. The proposed method improves the rate-distortion performance of conventional fast cost functions while maintaining low complexity requirement. As a result, the encoding process can be significantly accelerated with the use of the proposed cost function. Simulation results confirm that the proposed method reduces about 83.74 % computation of intra encoding of JM 12.4 encoder with negligible rate-distortion performance degradation.     

H.264中帧内编码算法及其快速实现研究

新的视频编码标准H.264使用了帧内预测的编码方式,这与以往的视频编码标准相比在很大程度上提高了帧内编码效率,节省了码流,但同时也增加了编码器的复杂度,因此有必要对H.264帧内编码算法进行快速实现,以满足实时视频通信的要求.首先详细介绍H.264帧内编码的实现过程,然后使用SIMD(单指令多数据流)技术对帧内编码进行快速实现.实验结果表明,与未使用快速算法相比,使用该快速实现算法后,H.264帧内编码速度得到显著提高.     

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.