可分级视频编码空域增强层的快速帧间模式选择算法

针对可分级视频编码(SVC)技术中层间残差预测(ILRP)大大增加了编码复杂度的问题,提出一种快速算法。带残差的帧间预测和不带残差的帧间预测都采用全搜索的预测算法,编码复杂度很大,所提算法分析了增强层带残差的帧间预测和不带残差的帧间预测之间的率失真代价(RDCost)差异,动态判定增强层是否需要采用层间残差预测以减少层间残差预测过程;同时依据层间预测模式相关性,利用基本层最优帧间预测模式指导增强层最优帧间预测模式的选择过程,进一步节省编码时间。实验结果表明,与参考模型JSVM中的算法相比,改进的快速算法在编码质量降低小于0.01dB,码率提高不大于3%的前提下,可节省平均编码时间50%左右,有效地降低了编码复杂度,对于编码器的优化方面有理论参考价值和实际应用意义。     

残差分布式视频压缩感知*

压缩感知(CS)是一种能同时进行数据采集和压缩的新理论,为简化编码算法提供了依据,同时,分布式视频编码(DVC)为低复杂度的视频编码提供了思路。因此,通过整合DVC和CS各自的特性以构建编码简单的视频编码框架,并采用残差技术来提高系统性能,最终提出了一种残差分布式视频压缩感知(RDCVS)算法:对关键帧进行传统的帧内编、解码;而对非关键帧,编码端采用一种基于残差联合稀疏模型的随机观测,解码端利用边信息和改进的梯度投影重建(GPSR)算法进行优化重构。由于将运动估计和变换编码等复杂度较高的运算转移到解码端进行,因而RDCVS保持了低复杂度的编码特性。实验结果表明,RDCVS算法比参考方案的恢复质量提高了2～3 dB。     

精细可伸缩视频编码中的增强层编码方法研究

提出了一种新的子带编码方法来对精细可伸缩视频编码中的增强层进行编码。在这种编码方法中,首先通过重排DCT残差系数形成子带,然后利用同一子带相邻系数的相关性来消除数据冗余。实验结果表明文章提出的增强层编码方法比原来的FGS增强层编码方法具有更高的编码效率。     

一种密集相机阵列的低复杂度视频压缩方法

为了降低多视点视频压缩的复杂度，根据密集相机阵列系统与Wyner—Ziv编码的特点，提出了基于Wyner—Ziv编码的密集相机阵列低复杂度视频压缩算法。该算法首先在各相机之间相互独立地采用基于感兴趣区提取的低复杂度来进行Wyner—ziv编码，然后在中心解码端利用各视点间的相关性进行联合解码。该算法是通过对DCT量化系数进行相似性判断来提取感兴趣区，以有效地避免对背景和平坦等区域进行编码，从而降低了编码复杂度。实验证明，该算法具有极低的编码复杂度特性和良好的率失真性能，编码复杂度仅为H．264帧间预测编码的1／22。     

改进的多视点立体视频FGS可分级方案

针对现有多视点立体视频FGS（Fine-Granular-Scalability）可分级方案编码效率低的问题进行改进,充分利用相邻视点之间的相似性,适应解码端质量优先或视点优先的不同需求,提出一种折衷方案,其中分I、P、B帧三种情况,以中间视点作为基本层进行编码,其他视点均预测自相邻视点部分恢复的FGS增强层,以此为基础产生当前视点的FGS增强层。实验证明,该方案具有更为灵活、广泛的可分级性能,更能适应用户对视点图像质量和立体观感的需求。     

基于内容统计分析的高清视频SVC快速模式选择算法

可伸缩编码(SVC)极大地增强了视频传输和解码的灵活性,而同时也极大地增加了编码的复杂度,使得实时应用变得更为困难。为此,本文提出了一个快速模式选择算法以加快编码器的速度。本算法首先统计增强层宏块的模式分布情况,然后估计视频序列的复杂度,并以此为根据为帧间最佳模式设置率失真代价门限。算法使用4个分辨率层(1080p,720p,VGA and QVGA),4个时域层,以及两个质量层进行测试,结果表明本算法能够在保持现有编码效率基本不变的情况下有效提高编码速度。     

基于统计的SVC层间编码快速模式决策算法

可分级视频编码提供了较为灵活的编码方式,但层间模式决策算法增加了编码器的计算复杂度。该文分析了基本层和增强层间模式分布的相关性,设计一种层间编码快速模式决策算法。实验结果表明,在PSNR平均仅降低0.04 dB、码率减少0.096%的前提下,该优化算法能使编码时间平均减少50.34%。     

H．264可分级扩展技术的介绍和分析

H．264可分级扩展是ISO／IEC组织和国际电信联盟最新的联合标准制订工作。目前，H．264扩展标准仍处于制订过程中，但其主体框架已基本确定。为了使人们对正在制定的H．264扩展标准有一概略了解。该文首先对扩展标准的主体框架作了简要介绍，并阐述了实现空域、时域和质量可分级的机制，然后对其中的层间编码和精细质量可分级编码包含的关键技术进行了较为详细的分析，并利用最新的参考软件JSVM5．7进行了性能以及复杂度的比较和测试，结果表明，该项技术在具有良好的支持分级能力的同时，可保持较高的编码效率。     

基于纹理区域分割的SVC快速模式决策算法

为降低可分级视频编码(SVC)模式决策的计算量,提出一种快速模式决策算法.利用INTRA模式率失真代价及其在层间的相关性,对增强层的图像纹理区域进行分割,使用提前终止阈值在SKIP模式、BLPRED模式中选择最佳模式,以INTRA模式率失真代价计算宏块的纹理区域类型,根据该区域类型以及运动活跃性,动态调整INTER模式...     

重用运动矢量和预测残差的MPEG-2/H.264空间分辨率转码

本文提出一种新的MPEG-2到H.264的视频转码算法.它通过充分利用MPEG-2解码过程中得到的运动矢量和宏块编码残差等信息,可显著减少H.264编码过程中宏码编码模式确定和运动估计过程的计算复杂度,并得到最终的H.264视频流.几种典型视频测试序列的仿真实验结果表明,本算法对视频质量的损失较小,有稳定的率失真性能,有利于实时转码的实现.     

H.264/SVC mode decision based on mode correlation and desired mode list

Design of video encoders involves implementation of fast mode decision (FMD) algorithm to reduce computation complexity while maintaining the performance of the coding. Although H.264/scalable video coding (SVC) achieves high scalability and coding efficiency, it also has high complexity in implementing its exhaustive computation. In this paper, a novel algorithm is proposed to reduce the redundant candidate modes by making use of the correlation among layers. A desired mode list is created based on the probability to be the best mode for each block in base layer and a candidate mode selection in the enhancement layer by the correlations of modes among reference frame and current frame. Our algorithm is implemented in joint scalable video model (JSVM) 9.19.15 reference software and the performance is evaluated based on the average encoding time, peak signal to noise ration (PSNR) and bit rate. The experimental results show 41.89% improvement in encoding time with minimal loss of 0.02 dB in PSNR and 0.05% increase in bit rate.     

Spatially scalable video coding with an efficient two-layered architecture

In this paper, an efficient spatially scalable video coding scheme with a two-layered architecture is proposed. In this architecture, two spatial layers are referred to as a base layer and an enhancement layer. The base layer is coded to be compatible to H.264 standard, and when coding the enhancement layer, a new inter layer intra coding method (ILICM) is used to improve the coding efficiency. ILICM intends to use a few specific pixels in the up-sampled and decoded base layer block to predict the corresponding block in enhancement layer, when those original predictors are not available. Besides, in order to interpolate the base layer data, a graceful component-based up-sampling method (CUSM) is also introduced in this paper. Based on the human vision system, CUSM assigns a much simpler up-sampling filter for the chroma component due to its lower sensitivity for human eyes. Generally, proposed schemes including ILICM and CUSM are expected to increase the coding performance of enhancement layer and reduce the computing complexity of the decoder, respectively. Experimental results show that, the PSNR values of luma component of encoded frames are increased with no additional cost on coded bit-rate for ILICM method, while CUSM method can also maintain the coding performance under the theoretically significant reduction of computational complexity.     

SPC: Fast and Efficient Scalable Predictive Coding of Animated Meshes

Animated meshes are often represented by a sequence of static meshes with constant connectivity. Due to their frame-based representation they usually occupy a vast amount of bandwidth or disk space. We present a fast and efficient scalable predictive coding (SPC) scheme for frame-based representations of animated meshes. SPC decomposes animated meshes in spatial and temporal layers which are efficiently encoded in one pass through the animation. Coding is performed in a streamable and scalable fashion. Dependencies between neighbouring spatial and temporal layers are predictively exploited using the already encoded spatio-temporal neighbourhood. Prediction is performed in the space of rotation-invariant coordinates compensating local rigid motion. SPC supports spatial and temporal scalability, and it enables efficient compression as well as fast encoding and decoding. Parts of SPC were adopted in the MPEG-4 FAMC standard. However, SPC significantly outperforms the streaming mode of FAMC with coding gains of over 33%, while in comparison to the scalable FAMC, SPC achieves coding gains of up to 15%. SPC has the additional advantage over FAMC of achieving real-time encoding and decoding rates while having only low memory requirements. Compared to some other non-scalable state-of-the-art approaches, SPC shows superior compression performance with gains of over 16% in bit-rate.     

基于MPEG-4的FGS视频压缩技术的研究

精细可伸缩性视频编码FGS(Fine Granular Scalable)是MPEG-4标准的视频化框架中的关键性的编码技术。FGS编码方法生成两个视频流：基本层码流和增强层码流。基本层码流是必须传输的，并且码率低；增强层码流则根据带宽的实际情况来决定传多少，甚至不传，这种分级性的编码方式和传输方式使视频流有较好的鲁棒性。     

H.264/AVC中基于决策树的P帧快速模式选择

目的 H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。为此提出一种针对P帧的基于决策树的快速候选模式选择算法。方法在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的变换域系数绝对值之和(SATD)值,采用决策树分类方法对其余宏块选择候选模式。结果由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间的节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

A flexible side information generation framework for distributed video coding

One of the most efficient approaches to generate the side information (SI) in distributed video codecs is through motion compensated frame interpolation where the current frame is estimated based on past and future reference frames. However, this approach leads to significant spatial and temporal variations in the correlation noise between the source at the encoder and the SI at the decoder. In such scenario, it would be useful to design an architecture where the SI can be more robustly generated at the block level, avoiding the creation of SI frame regions with lower correlation, largely responsible for some coding efficiency losses. In this paper, a flexible framework to generate SI at the block level in two modes is presented: while the first mode corresponds to a motion compensated interpolation (MCI) technique, the second mode corresponds to a motion compensated quality enhancement (MCQE) technique where a low quality Intra block sent by the encoder is used to generate the SI by doing motion estimation with the help of the reference frames. The novel MCQE mode can be overall advantageous from the rate-distortion point of view, even if some rate has to be invested in the low quality Intra coding blocks, for blocks where the MCI produces SI with lower correlation. The overall solution is evaluated in terms of RD performance with improvements up to 2 dB, especially for high motion video sequences and long Group of Pictures (GOP) sizes.     

H.264/AVC中基于决策树的P帧快速模式选择（HHME2013第61号论文）

目的：H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。本文提出了一种针对P帧的基于决策树的快速选择候选模式算法。方法：在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的SATD值,采用决策树分类方法对其余宏块选择候选模式。结果：由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论：本文提出了一种新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

无损自适应分布式算术编码的研究及应用

目前分布式算术编码研究都是基于先验概率已知的有损压缩,为了实现概率自适应的无损压缩,研究了采用结束字符和概率自适应的编码方式来实现编码,提出了无损自适应分布式算术编码。实验结果表明,该算法拥有更好的压缩效果和更低的解码复杂度,并且在实际应用中,编解码可以同时进行。由于无损自适应分布式算术编码具有编码简单、压缩效果好的优点,故将它和比特面编码结合实现超光谱图像压缩,并将仿真结果与3D-SPECK算法比较,结果表明了该方法可以使信噪比提高0.13-0.37dB。     

一种高效的CABAC解码器硬件结构设计

相对于其他熵编码而言,基于上下文的自适应二进制算术熵编码（CABAC）具有更大的数据压缩率,但由于其运算复杂,访问存储设备频繁,导致编／解码率较低。针对影响CABAC解码速度的“瓶颈”问题,提出了一种高效的CABAC解码器硬件结构,包括新的存储访问方式、优化的解码核心单元结构以及子解码器级联的方式。实验结果表明,该硬件结构可显著提高CABAC的解码效率。