H.264视频编码帧间与帧内预测模式算法的改进

H.264是目前应用最广泛的视频编码标准,相比于以前的标准,H.264在编码效率上得到了很大的提高.但是相应的计算复杂度也是成倍增加.在此提出一种改进的预测算法,通过时域相关性系数和空域相关性系数排除帧内预测或帧外预测的一些模式,初步减少编码复杂度,再针对分析结果利用已有的快速选择算法对帧内帧外预测模式的最优预测模式组进行预测,进一步加快编码速度.实验结果表明,改进的快速算法在不影响编码质量的同时能够有效地减少计算复杂度和提高编码速度.     

H.264帧内模式快速选择算法研究

在对校验模型帧内预测算法分析的基础上,提出了一种帧内模式快速选择算法:在帧内编码中采用亮色分离方案对模式进行选择,在帧间编码中利用最佳帧间模式信息对帧内预测模式进行选择.实验证明,与原校验模型JM72相比,平均编码速度提高约29%,亮度PSNR平均下降在0.01 dB之内,平均比特率上升约0.34%.     

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。     

一种快速HEVC帧内算法

为了提高HEVC帧内预测的编码速度,本文提出了一种快速帧内预测算法。该算法充分利用视频序列的时间相关性,利用相邻帧CU的大小相关性在CU（Code Unit）层提前判定CU的最佳编码尺寸以及利用相邻帧在PU层减少预测方向数目来加速帧内预测的过程。实验结果表明：本文提出的算法与HEVC已有快速算法相比,峰值信噪比（PSNR）平均下降0.06dB,输出码率平均减少0.09%,而帧内预测时间平均减少了约49.81%。     

一种快速HEVC帧内预测算法

为了提高HEVC帧内预测的编码速度,提出了一种快速帧内预测算法。该算法充分利用视频序列的时间相关性,利用相邻帧CU的大小相关性在CU(Code Unit)层提前判定CU的最佳编码尺寸以及利用相邻帧在PU层减少预测方向数目来加速帧内预测的过程。实验结果表明:提出的算法与HEVC已有快速算法相比,峰值信噪比(PSNR)平均下降0.06 dB,输出码率平均减少0.09%,而帧内预测时间平均减少了约49.81%。     

DCT域HEVC帧内预测模式映射算法研究

高效视频编码(HEVC)算法支持的帧内预测模式扩展到了35种,使之可实现更精准的预测,从而取得更高的压缩率。通过分析图像数据DCT系数的特性,研究了DCT系数与帧内预测模式的映射关系,提出了一种DCT系数的分布特征与帧内预测模式间的映射方法,该方法可用于提高HEVC的编码速度。     

面向AVS2的快速帧间预测算法北大核心

新一代具有自主知识产权的视频编码标准AVS2正在制定当中,其相对于上一代标准而言具有更高的编码效率,但由于使用了多划分模式、多参考帧等技术,其编码复杂度也大幅增加。为了提高AVS2帧间编码速度,提出了一种快速帧间预测算法,在使用非对称运动划分(Asymmetric Motion Partitions,AMP)快速决策算法的基础上,深度挖掘同一编码单元下相邻预测单元之间的相关性,利用邻近预测单元来预测当前块的参考帧,通过判断预测单元的运动矢量残差的曼哈顿距离,以确定最佳参考帧,从而减小参与计算的参考帧数目。实验结果表明,该算法在图像质量和比特率基本保持不变的情况下,有效地提高了AVS2的编码速度。     

面向AVS2的快速帧间预测算法

新一代具有自主知识产权的视频编码标准AVS2正在制定当中,其相对于上一代标准而言具有更高的编码效率,但由于使用了多划分模式、多参考帧等技术,其编码复杂度也大幅增加。为了提高AVS2帧间编码速度,提出了一种快速帧间预测算法,在使用非对称运动划分(Asymmetric Motion Partitions,AMP)快速决策算法的基础上,深度挖掘同一编码单元下相邻预测单元之间的相关性,利用邻近预测单元来预测当前块的参考帧,通过判断预测单元的运动矢量残差的曼哈顿距离,以确定最佳参考帧,从而减小参与计算的参考帧数目。实验结果表明,该算法在图像质量和比特率基本保持不变的情况下,有效地提高了AVS2的编码速度。     

一种图像DCT数据与HEVC帧内预测模式之间的映射方法

【】高效视频编码(HEVC)算法支持的帧内预测模式扩展到了35种,使之可实现更精准的预测,从而取得更高的压缩率。本文通过分析图像数据DCT系数的特性,研究了DCT系数与帧内预测模式的映射关系,提出了一种DCT系数的分布特征与帧内预测模式间的映射方法,该方法可用于提高HEVC的编码速度。     

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。     

一种基于自相关法的H.264/AVC高效帧内预测算法

H.264/AVC是最新的视频压缩标准,具有极高的压缩率,但由于编码时间较长,无法达到实时应用的要求.本文提出了一种新的基于自相关法的高效帧内预测算法.该算法在进行帧内预测之前先对宏块预判,从两种预测模式中选择一种,从而减少了算法的复杂度.实验结果表明,本文提出的算法在码率只有少许增加的情况下,速度平均提高了26.9%,SNR值基本维持不变.     

融合宏块平坦度和时空相关性的预测模式选择算法

H.264/AVC以巨大编码复杂度为代价,在获得更高压缩率的同时,编码实时性也随之降低。针对视频编码中重要且耗时的帧间预测技术,分析了宏块平坦度和时空相关性,提出了一种快速的预测模式选择算法。仿真实验结果表明,本文提出算法与H.264/AVC(JM12.2)标准算法相比,在保持重建视频图像质量和输出码流结构的前提下,平均节省约70%的编码时间,并继承了H.264/AVC低码率的编码优势。     

Mode-Dependent Templates and Scan Order for H.264/AVC-Based Intra Lossless Coding

In H.264/advanced video coding (AVC), lossless coding and lossy coding share the same entropy coding module. However, the entropy coders in the H.264/AVC standard were original designed for lossy video coding and do not yield adequate performance for lossless video coding. In this paper, we analyze the problem with the current lossless coding scheme and propose a mode-dependent template (MD-template) based method for intra lossless coding. By exploring the statistical redundancy of the prediction residual in the H.264/AVC intra prediction modes, more zero coefficients are generated. By designing a new scan order for each MD-template, the scanned coefficients sequence fits the H.264/AVC entropy coders better. A fast implementation algorithm is also designed. With little computation increase, experimental results confirm that the proposed fast algorithm achieves about 7.2% bit saving compared with the current H.264/AVC fidelity range extensions high profile.     

VLC table prediction for CAVLC in H.264/AVC using correlation,statistics, and structural characteristics of mode information

The H.264/AVC video coding standard adopted context-based adaptive variable length coding (CAVLC) as an entropy coding tool. By combining adaptive variable length coding (VLC) with context modeling, we can achieve a high coding performance. However, CAVLC in H.264/AVC has the problem that VLC table prediction is not always accurate. In this paper, we propose a new VLC table prediction algorithm using the correlation between coding modes of the current and neighboring sub-blocks and the statistics of mode distribution in both intra and inter frames. In addition, we can further increase correctness of VLC table prediction considering the structural characteristics of mode information in inter frames. Experimental results show that the proposed algorithm increases correctness of VLC table prediction by 10.07% and reduces the bit rate by 1.21% on average without significant increment of encoding time.     

一种基于H.264/AVC压缩域的GOP级视频场景转换检测算法

本文提出了一种基于H.264/AVC压缩域的GOP(Group of Pictures)级视频场景转换检测算法.该算法利用H.264/AVC基本档次码流中的帧内预测模式、运动矢量和宏块编码类型等可用信息,提出了基于子块的色度模式差异、累积运动值和累积帧内宏块数等三个判决准则,然后综合利用这三个判决准则,提出了一种GOP级的视频场景转换检测算法.实验结果表明,与现有的一个COP级场景检测算法对比,本文提出的GOP级视频场景转换检测算法可以获得更好的检测性能.     

Fast block mode decision algorithm in H.264/AVC video coding

The recent video coding standard H.264/AVC show extremely higher coding efficiency compare to any other previous standards. H.264/AVC can achieve over 50% of bit rate saving with same quality using the rate–distortion process, but it brings high computational complexity. In this paper, we propose an algorithm that can reduce the complexity of the codec by reducing the block mode decision process adaptively. Block mode decision process in H.264/AVC consists of inter mode decision process and intra mode decision process. We deal with reduction method for inter and intra mode decision. In this paper an efficient method is proposed to reduce the inter mode decision complexity using the direct prediction methods based on block correlation and adaptive rate distortion cost threshold for early stopping. The fast intra mode reduction algorithm based on inter mode information is also proposed to reduce the computational complexity. The experimental results show that the proposed algorithm can achieve up to 63.34–77.39% speed up ratio with a little PSNR loss. Increment in bit requirement is also not much noticeable.     

General Architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC Intra Frame Transcoding

The latest international video-coding standard H.264/AVC significantly achieves better coding performance compared to prior video coding standards such as MPEG-2 and H.263, which have been widely used in today’s digital video applications. To provide the interoperability between different coding standards, this paper proposes an efficient architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC intra frame transcoding, using the original information such as discrete cosine transform (DCT) coefficients and coded mode type. Low-frequency components of DCT coefficients and a novel rate distortion cost function are used to select a set of candidate modes for rate distortion optimization (RDO) decision. For H.263 and H.264/AVC, a mode refinement scheme is utilized to eliminate unlikely modes before RDO mode decision, based on coded mode information. The experimental results, conducted on JM12.2 with fast C8MB mode decision, reveal that average 58%, 59% and 60% of computation (re-encoding) time can be saved for MPEG-2, H.263, H.264/AVC to H.264/AVC intra frame transcodings respectively, while preserving good coding performance when compared with complex cascaded pixel domain transcoding (CCPDT); or average 88% (a speed up factor of 8) when compared with CCPDT without considering fast C8MB. The proposed algorithm for H.264/AVC homogeneous transcoding is also compared to the simple cascaded pixel domain transcoding (with original mode reuse). The results of this comparison indicate that the proposed algorithm significantly outperforms the mode reuse algorithm in coding performance, with only slightly higher computation.     

H．264／AVC帧内预测模式不同快速算法的分析

快速帧内预测模式选择是一项提高H.264/AVC压缩性能的关键技术。H.264/AVC通过采用RDO(率失真优化)模式获得编码的性能提高,但这是以高计算复杂度为代价的。为了解决这个问题,首先对H.264/AVC的帧内预测算法进行研究,随后对不同快速算法进行分析,证明其都以不同方式大幅度提高了H.264/AVC帧内预测的速度,同时保持了较高的预测精度和主观图像质量。     

Fast Interframe mode decision algorithm based on mode mapping and MB activity for MPEG-2 to H.264/AVC transcoding

Recently the latest video coding standard H.264/AVC is widely used for the mobile and low bitrate video codec in the various multimedia terminals. On the other hand, the MPEG-2 MP@HL codec has become the center of digital video contents since it is the standard codec for the Digital TV (DTV). To provide the bridge between the contents in MPEG-2 and mobile terminals, the transcoding of MPEG-2 contents into H.264/AVC format is an inevitable technology in the digital video market. The main bottleneck in the process lies in the computational complexity. In H.264/AVC, the variable block size (VBS) mode decision (MD) is used in the Interframe for the improved performance in the motion compensated prediction. For the macroblock (MB) which cannot be accurately predicted with one motion vector (MV), it is partitioned into smaller blocks and predicted with different MVs. In addition, SKIP and Intra modes are also permitted in the Interframe MD of H.264/AVC to further ameliorate the encoding performance. With the VBS MD technology, the Inter prediction accuracy can be improved significantly. However, the incidental side-effect is the high computational complexity. In this paper, we propose a fast Interframe MD algorithm for MPEG-2 to H.264/AVC transcoding. The relationships between SKIP and Intra modes are detected at first to map these two kinds of modes directly from MPEG-2 to H.264/AVC. And then the MB activity will be scaled by the residual DCT energy obtained from the MPEG-2 decoding process to estimate the block sizes of the MB mode for H.264/AVC Interframe MD. In our proposed method, the original redundant candidate modes can be eliminated effectively, resulting in the reduction of the computational complexity. It can reduce about 85% Rate-to-Distortion Cost (RDCost) computing and 45% entire processing time compared with the well-known cascaded transcoder while maintaining the video quality.     

Efficient 45nm ASIC Architecture for Full-Search Free Intra Prediction in Real-Time H.264/AVC Decoder

The standard H.264/AVC Intra frame encoding process has several data dependent and computational intensive coding methodologies that limit the overall encoding speed. It causes not only a high degree of computational complexity but also an unacceptable delay especially for the real-time video applications. Based on DCT properties and spatial activity analysis, low power hardware architecture for high throughput Full-Search Free (FSF) Intra mode selection and direction prediction algorithm is proposed. The FSF Intra prediction Algorithm significantly reduces the computational complexity and the processing run-time required for the H.264/AVC Intra frame prediction process. The ASIC implementation for the proposed architecture is carried out and synthesizing results are obtained. The heavily tested 45nm ASIC design is able to achieve an operating frequency of 140 MHz while limiting the overall power consumption to 9.01 mW, which nominates our proposed FSF Intra prediction architecture for interactive real-time H.264/AVC mobile video decoders.