基于双向运动补偿的三维小波变换方法

提出了基于双向运动补偿的三维小波变换方法,与以往的三维小波变换方法相比较,该方法在三维小波视频编码方法中应用了双向的运动估计/补偿,进而实现了两种时域可扩展方式的组合,提高了视频编码的可扩展性。     

Fuzzy quantization based bit transform for low bit-resolution motion estimation

This study proposes a novel fuzzy quantization based bit transform for low bit-resolution motion estimation. We formalize the procedure of bit resolution reduction by two successive steps, namely interval partitioning and interval mapping. The former is a many-to-one mapping which determines motion estimation performance, while the latter is a one-to-one mapping. To gain a reasonable interval partitioning, we propose a non-uniform quantization method to compute coarse thresholds. They are then refined by using a membership function to solve the mismatch of pixel values near threshold caused by camera noise, coding distortion, etc. Afterwards, we discuss that the sum of absolute difference (SAD) is one of the fast matching metrics suitable for low bit-resolution motion estimation in the sense of mean squared errors. A fuzzy quantization based low bit-resolution motion estimation algorithm is consequently proposed. Our algorithm not only can be directly employed in video codecs, but also be applied to other fast or complexity scalable motion estimation algorithms. Extensive experimental results show that the proposed algorithm can always achieve good motion estimation performances for video sequences with various characteristics. Compared with one-bit transform, multi-thresholding two-bit transform, and adaptive quantization based two-bit transform, our bit transform separately gains 0.98 dB, 0.42 dB, and 0.24 dB improvement in terms of average peak signal-to-noise ratio, with less computational cost as well.     

3D Color Set Partitioning in Hierarchical Trees

This paper introduces the 3D color set partitioning in hierarchical trees (3D-CSPIHT) low bit rate embedded video coding scheme. The codec exploits the correlation between temporal and spatial wavelet coefficients and the interdependency between luminance and chrominance components to code color video sequences without the need for explicit bit allocation. Besides offering rate scalability, the new codec also produces multi-resolution scalable code streams. The hierarchical variable size block matching motion estimation technique is also integrated to demonstrate the motion estimation option with 3D-CSPIHT. The coding results show that 3D-CSPIHT produces better performance and visual quality compared to 3D-SPIHT.     

Video coding scheme using DCT-pyramid vector quantization

A new and effective video coding scheme for contribution quality is proposed. The CMTT/2, a joint committee of CCIR and CCITT, has proposed a video coding scheme (already approved at European level by ETS) working at 34-45 Mbit/s. Basically this proposal includes a DCT transform for spatial correlation removal and motion compensation for temporal correlation removal. The individual transform coefficients are then scalar quantized with a non uniform bit assignment. Starting from the CMTT/2 proposal, the study presents a new video coding scheme designed using a vector quantizer solution instead of the scalar one. Specifically, the pyramid vector quantization (PVQ) has been chosen as the vector quantization method as it is able to reduce the DCT coefficients Laplacian distribution. Simulation results show that the proposed video coding scheme gives the same contribution quality at 22 Mbit/s as the one obtained with the CMTT/2 proposal at 45 Mbit/s.     

一种新的小波可视电话编码算法

针对极低比特率应用提出一种新的结合H.263与SLCCA的混合小波视频编码算法。在提出的算法中,首先,用基于H.263的微调运动估计减小时间冗余,用无遗漏覆盖块运动补偿保证运动补偿误差帧的连续性;第二,对运动补偿误差帧进行小波变换得到全局能量压缩;第三,用SLCCA组织和表示小波变换后的数据,最后,运动向量的水平和垂直分量分别用自适应算法编码,算法在A级测试序列Akiyo和B级测试序列Foreman（QFIF）上测试取得了良好效果。     

Lifting-based invertible motion adaptive transform (LIMAT) framework for highly scalable video compression

We propose a new framework for highly scalable video compression, using a lifting-based invertible motion adaptive transform (LIMAT). We use motion-compensated lifting steps to implement the temporal wavelet transform, which preserves invertibility, regardless of the motion model. By contrast, the invertibility requirement has restricted previous approaches to either block-based or global motion compensation. We show that the proposed framework effectively applies the temporal wavelet transform along a set of motion trajectories. An implementation demonstrates high coding gain from a finely embedded, scalable compressed bit-stream. Results also demonstrate the effectiveness of temporal wavelet kernels other than the simple Haar, and the benefits of complex motion modeling, using a deformable triangular mesh. These advances are either incompatible or difficult to achieve with previously proposed strategies for scalable video compression. Video sequences reconstructed at reduced frame-rates, from subsets of the compressed bit-stream, demonstrate the visually pleasing properties expected from low-pass filtering along the motion trajectories. The paper also describes a compact representation for the motion parameters, having motion overhead comparable to that of motion-compensated predictive coders. Our experimental results compare favorably to others reported in the literature, however, our principal objective is to motivate a new framework for highly scalable video compression.     

Hybrid picture coding with wavelet transform and overlappedmotion-compensated interframe prediction coding

A novel video coding scheme using an orthonormal wavelet transform is proposed. The wavelet transform is used in a motion compensated interframe coder in which a blockless motion compensation technique is employed to increase efficiency of wavelet transform coding. A new scanning method for wavelet coefficients is also proposed which is rather different from subband coding. Simulation work is carried out to evaluate the proposed coding method. Significant improvement in subjective quality is obtained over that obtained with conventional hybrid coding methods that use blockwise motion compensation and DCT. Some improvement has also been realized in the signal to noise ratio. Although wavelet coding is still in its early stages of development, it appears to hold great promise for motion picture coding     

Highly scalable video compression with scalable motion coding

A scalable video coder cannot be equally efficient over a wide range of bit rates unless both the video data and the motion information are scalable. We propose a wavelet-based, highly scalable video compression scheme with rate-scalable motion coding. The proposed method involves the construction of quality layers for the coded sample data and a separate set of quality layers for the coded motion parameters. When the motion layers are truncated, the decoder receives a quantized version of the motion parameters used to code the sample data. The effect of motion parameter quantization on the reconstructed video distortion is described by a linear model. The optimal tradeoff between the motion and subband bit rates is determined after compression. We propose two methods to determine the optimal tradeoff, one of which explicitly utilizes the linear model. This method performs comparably to a brute force search method, reinforcing the validity of the linear model itself. Experimental results indicate that the cost of scalability is small. In addition, considerable performance improvements are observed at low bit rates, relative to lossless coding of the motion information.     

A progressive transmission image coder using linear phase uniformfilterbanks as block transforms

This paper presents a novel image coding scheme using M-channel linear phase perfect reconstruction filterbanks (LPPRFBs) in the embedded zerotree wavelet (EZW) framework introduced by Shapiro (1993). The innovation here is to replace the EZWs dyadic wavelet transform by M-channel uniform-band maximally decimated LPPRFBs, which offer finer frequency spectrum partitioning and higher energy compaction. The transform stage can now be implemented as a block transform which supports parallel processing and facilitates region-of-interest coding/decoding. For hardware implementation, the transform boasts efficient lattice structures, which employ a minimal number of delay elements and are robust under the quantization of lattice coefficients. The resulting compression algorithm also retains all the attractive properties of the EZW coder and its variations such as progressive image transmission, embedded quantization, exact bit rate control, and idempotency. Despite its simplicity, our new coder outperforms some of the best image coders published previously in the literature, for almost all test images (especially natural, hard-to-code ones) at almost all bit rates.     

Scalable video compression via overcomplete motion compensated wavelet coding

Recently, there have been a flurry of works on overcomplete motion compensated wavelet coding (OMCWC). In this paper, we address the importance of phase and focus on the design of scalable video coding algorithms within the OMCWC framework. Specifically, our new contributions consist of the following three components: (1) efficient block motion estimation techniques in the wavelet domain including hierarchical and fractional-pel block matching, (2) extend overcomplete motion compensated prediction (MCP) into overcomplete motion compensated temporal filtering (MCTF) to achieve temporal scalability (3) context modeling strategies for embedded quantization and entropy coding of 3D wavelet coefficients. Experiment results are used to demonstrate that the class of overomplete MCP/MCTF coders are capable of achieving comparable performance to other competing interframe wavelet coders.     

Motion-compensated wavelet transform coder for very low bit-rate visual telephony

This paper proposes a new motion-compensated wavelet transform video coder for very low bit-rate visual telephony. The proposed coder sequentially employs: (1) selective motion estimation on the wavelet transform domain, (2) motion-compensated prediction (MCP) of wavelet coefficients, and (3) selective entropy-constrained vector quantization (ECVQ) of the resultant MCP errors. The selective schemes in motion estimation and in quantization, which efficiently exploit the characteristic of image sequences in a visual telephony, considerably reduce the computational burden. The coder also employs a tree structure encoding to represent efficiently which blocks were encoded. In addition, in order to reduce the number of ECVQ codebooks and the image dependency of their performance, we introduce a preprocessing of signals which normalizes input vectors of ECVQ. Simulation results show that our video coder provides good PSNR (peak-to-peak signal-to-noise ratio) performance and efficient rate control.     

Low bit-rate video coding using wavelet vector quantisation

A method for low bit-rate video coding based on wavelet vector quantisation is proposed. Motion estimation/compensation using overlapped block matching (OBM) is employed to eliminate the blocking effects in the prediction error introduced by conventional block matching. It is shown that OBM significantly increases the efficiency of the wavelet transform coder. The motion-compensated interframe prediction error is decomposed using a wavelet transform and a method is employed for the efficient coding of the wavelet coefficients. In this technique, the coefficients are coded with a zero-tree multistage lattice vector quantiser. Simulation results are provided to evaluate the coding performance of the described coding scheme for low bit-rate video coding. It provides constant bit rate, obviating the need for buffer, with just small fluctuations in PSNR. Moreover, comparison with the RM8 implementation of the standard H261 video coder shows that the presented codec provides improvements in both peak signal-to-noise ratio and picture quality     

Drift controlled scalable wavelet based video coding in the overcomplete discrete wavelet transform domain

Traditional video coders use the previous frame to perform motion estimation and compensation. Though they are less complex and have minimum coding delays, these coders lose their efficiency when subjected to scalability requirements. Recent 3D wavelet coders using lifting schemes offer high compression efficiency and scalability without significant loss in performance. The main drawback of 3D coders is that they process several frames at a time. This introduces additional delay, which makes them less suitable for real time applications.In this work, we propose a novel scheme to minimize drift in scalable wavelet based video coding, which gives a balanced performance between compression efficiency and reconstructed quality with less drift. Our drift control mechanism maintains two frame buffers in the encoder and decoder; one that is based on the base layer and one that is based on the base plus enhancement layers. Drift control is achieved by switching between these two buffers for motion estimation and compensation. Our prediction is initially based on the base plus enhancement layers buffer, which inherently introduces drift in the system if a part of the enhancement layer is not available at the receiver. A measure of drift is computed based on the channel information and a threshold is set. When the measure exceeds the threshold, i.e., when drift becomes significant, we switch the prediction to be based on the base layer buffer, which is always available to the receiver. We also developed an adaptive scheme with additional computation overhead at the encoder to decide the switching instance. The performance of the threshold case that needs fewer computations is comparable with the adaptive scheme. Our coder offers high compression efficiency and sustained video quality for variable bit rate wireless channels. This proves that we need not completely eliminate drift and decrease compression efficiency to get better received video quality.     

Motion compensated image interpolation

Field skipping is a variable technique for reducing drastically the bit rate necessary to transmit a television signal. All fields have to be reconstructed at the receiver end, but nearest-neighbor or linear interpolations give poor performances when significant scene activity is present; therefore, some motion compensation scheme is mandatory. Although any of the algorithms proposed for motion estimation can be used for motion compensated interpolation, in this paper only the pel-recursive algorithm is considered. Past experience is briefly summarized and, based on criticism, improvements to the basic algorithm are proposed that seem to lead to an estimated motion field that is accurate enough. Multiple recursions and appropriate selection rules are proposed to counteract streaking effects of the recursive algorithm when it crosses image boundaries. The estimation of a forward and a backward motion field is used to identify image areas where occlusion effects are present. Experimental results are presented that seem to indicate that the proposed interpolation scheme has good performance     

基于BWT和FVQ的极低比特率图像编码算法

该文提出了一种基于双正交小波变换(BWT)和模糊矢量量化(FVQ)的极低比特率图像编码算法。该算法通过构造符合图像小波变换系数特征的跨频带矢量,充分利用了不同频带小波系数之间的相关性,有效地提高了图像的编码效率和重构质量。该算法采用非线性插补矢量量化(NLIVQ)的思想,从大维数矢量中提取小维数的特征矢量,并提出了一种新的模糊矢量量化方法一渐进构造模糊聚类(PCFC)算法用于特征矢量的量化,从而大大提高了矢量量化的速度和码书质量。实验结果证明,该算法在比特率为0．172bpp的条件下仍能获得PSNR＞30dB的高质量重构图像。     

一个优化小波块量化矩阵的算法

小波变换以其良好的空间－频率局部特性,在图像编码标准JPEG2000和MPEG4中占据了重要位置.本文选用正交小波基对图像做小波变换,然后重新组织小波系数成小波块,最后提出了一个构造小波块量化矩阵以产生最优比特分配的算法.本算法用一种新的方式统计小波系数分布,并结合人体视觉系统的特点,采用动态策略在很大的比特率范围内产生最优的小波块量化矩阵.     

自适应分区DCT/DWT低码率视频编码算法

为了降低低码率视频编码算法的块效应与环效应，提出了一种基于自适应分区余弦变换／子波变换和重叠运动补偿的视频编码算法，首先给了一种空－是相关自适应运动估计算法，有效降低运算复杂性，然后通过过层游动窗块区域形成算法检测现帧间预测误差场的高能量区域，对大区域进行了子波变换和量化，对零散区域进行余弦变换和量化，根据人类视觉系统（ＨＶＳ）的空－频和时－频特性，给出基于ＨＶＳ的量化模型，以期在信噪比约束下获得     

Perceptual feedback in multigrid motion estimation using animproved DCT quantization

In this paper, a multigrid motion compensation video coder based on the current human visual system (HVS) contrast discrimination models is proposed. A novel procedure for the encoding of the prediction errors has been used. This procedure restricts the maximum perceptual distortion in each transform coefficient. This subjective redundancy removal procedure includes the amplitude nonlinearities and some temporal features of human perception. A perceptually weighted control of the adaptive motion estimation algorithm has also been derived from this model. Perceptual feedback in motion estimation ensures a perceptual balance between the motion estimation effort and the redundancy removal process. The results show that this feedback induces a scale-dependent refinement strategy that gives rise to more robust and meaningful motion estimation, which may facilitate higher level sequence interpretation. Perceptually meaningful distortion measures and the reconstructed frames show the subjective improvements of the proposed scheme versus an H.263 scheme with unweighted motion estimation and MPEG-like quantization.     

Flexible three-band motion-compensated temporal filtering for scalable video coding

A novel scheme for scalable video coding using three-band lifting-based motion-compensated transform is presented in this article. A series of flexible three-band motion-compensated lifting steps are used to implement the temporal wavelet transform, which provide improved compression performance by selecting specific motion model according to real video sequences, and offer higher temporal scalability flexibility by using three-band lifting steps. The experimental results compared with motion picture expert group (MPEG)-4 codec concerning standard video sequences demonstrate the effectiveness of the method.     

An effective mesh-based motion compensation technique for video coding

The block-matching algorithm is the most popular motion compensation technique in video coding. However, it cannot provide acceptable quality at very low bit rate. In this paper, a new mesh-based motion compensation method is proposed to attack the problem. First, a regular non-uniform mesh, which has regular structure with variable patch size, is presented. The patch size is varied according to motion activity of a video sequence. Next, a weighted interpolation block matching is developed to improve the estimate accuracy of displacements of grid points. It utilizes the motion correlation between a grid point and its associated patches. Finally, based on the new mesh and motion estimation scheme, an efficient motion compensation algorithm is developed. When compared to the conventional motion compensation techniques, the proposed method improves performance significantly with lower computational complexity and overhead information bits.