Very Low Bit-Rate Video Coding Based on Wavelet Transform

Two video coding schemes based on wavelet transform achieving very low bit rate are presented in this paper. The first is a hybrid motion compensated wavelet transform(MC WT)system which behaves better at very low bit rates than the block DCT residual coder. The second is a new efficient coding system based on a simple frame differencing wavelet transform(FD WT)which performs well in both PSNR and visual quality with substantially reduced complexity.

3-D Wavelet Transform for Very Low Bit-Rate Video Coding

A new improved Goh's 3 D wavelet transform(WT) coding scheme is presented in this paper. The new scheme has great advantages including a simple code structure, low computation cost and good performance in PSNR, compression ratios and visual quality of reconstructions, when compared to the other existing 3 D WT coding methods and the 2 D WT based coding methods. The new 3 D WT coding scheme is suitable for very low bit rate video coding.

Very Low Bit Rate Video Coding Using Motion Compensated 3 D Wavelet Transform

A new motion compensated 3 D wavelet transform (MC 3DWT) video coding scheme is presented in this paper. The new coding scheme has a good performance in average PSNR, compression ratio and visual quality of reconstructions compared with the existing 3 D wavelet transform (3DWT) coding methods and motion compensated 2 D wavelet transform (MC WT) coding method. The new MC 3DWT coding scheme is suitable for very low bit rate video coding.

Low Bit Rate Underwater Video Image Compression and Coding Method Based on Wavelet Decomposition

In view of the limited bandwidth of underwater video image transmission,a low bit rate underwater video compression coding method is proposed.Based on the preprocessing process of wavelet transform and coefficient down-sampling,the visual redundancy of underwater image is removed and the computational coefficients and coding bits are reduced.At the same time,combined with multi-level wavelet decomposition,inter frame motion compensation,entropy coding and other methods,according to the characteristics of different types of frame image data,reduce the number of calculations and improve the coding efficiency.The experimental results show that the reconstructed image quality can meet the visual requirements,and the average compression ratio of underwater video can meet the requirements of underwater acoustic channel transmission rate.

Variable Bit Rate Fuzzy Control for Low Delay Video Coding

Rate control plays a critical role in achieving perceivable video quality under a variable bit rate,limited buffer sizes and low delay applications.Since a rate control system exhibits non-linear and unpredictable characteristics,it is difficult to establish a very accurate rate-distortion(R-D)model and acquire effective rate control performance.Considering the excellent control ability and low computing complexity of the fuzzy logic in non-linear systems,this paper proposes a bitrate control algorithm based on a fuzzy controller,named the Fuzzy Rate Control Algorithm(FRCA),for All-Intra(AI)and low-delay(LD)video source coding.Contributions of the proposed FRCA mainly consist of four aspects.First,fuzzy logic is adopted to minimize the deviation between the actual and the target buffer size in the hypothetical reference decoder(HRD).Second,a fast lookup table is employed in fuzzy rate control,which reduces computing cost of the control process.Third,an input domain determination scheme is proposed to improve the precision of the fuzzy controller.Fourth,a novel scene change detection is introduced and integrated in the FRCA to adaptively adjust the Group-of-Pictures(GOP)length when the source content fluctuates.The FRCA can be transplanted and implemented in various industry coders.Extensive experiments show that the FRCA has accurate variable bit-rate control ability and maintains a steady buffer size during the encoding processes.Compared with the default configuration encoding under AI and LD,the proposed FRCA can achieve the target bit rates more accurately in various classical encoders.

Frame-layer bit allocation for multi-view video coding based on frame complexity estimation

Current multi-view video coding （MVC） reference model in joint video team （JVT） does not provide efficient rate control schemes. This paper presents a rate control algorithm for MVC by improving the quadratic rate-distortion （R-D） model. We reasonably allocate bit-rate among views based on the correlation analysisl The proposed algorithm consists of three levels to control the rate bits more accurately, of which the frame layer allocates bits according to the frame complexity and the temporal activity. Extensive experiments show that the proposed algorithm can control the bit rate efficiently.

AVariablebitrateVideoCodingSchemeBasedonMorphologicalOperationsforATMNetworks

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A rate control scheme for H.264 video under low bandwidth channel

The dilemma of the quantization parameter (QP) being involved in both rate control and rate-distortion optimization (RDO) prevents using the traditional rate control scheme. Although some rate control schemes are proposed to circumvent the dilemma, the inaccurate prediction model and improper bit allocation deter H.264 application on low bandwidth channel. To resolve this issue, this paper proposes a novel rate control scheme by considering the macroblock (MB) encoding complexity variation and buffer variation and by exploiting the spatio-temporal correlation sufficiently well. Simulations showed that this scheme improves the perceptual quality of the pictures with similar or smaller PSNR deviations when compared to that of rate control in JVT-O016.

A Modified Block Matching Motion Estimation Algorithm for the Very Low Bit-Rate video Coding

Block matching motion estimation techniques have been widely used in video coding applications. However, they also show their deficiency in the coherence of motion vectors and antinoise ability. This paper proposes a modified algorithm which can adopt any one of existing search algorithms and pays more attention to the correlation of neighboring blocks.It will be shown that the proposed algorithm is simple and significantly reduces the computational complexity. Simulation results also show that this algorithm improves the smoothness of the motion field, hence reducing the cost to code the motion vectors while keeping good performance comparable with the conventional block matching motion estimation algorithm.

基于模糊量化和2 bit深度像素的运动估计算法

提出了一种2 bit深度像素的运动估计算法。首先,将像素深度的降采样过程形式化为区间分划和区间映射2个步骤,其中前者为多对一映射,决定着运动估计性能,后者为一一映射;其次,提出一种非均匀量化方法求解区间分划的3个初始阈值,并利用隶属度函数对初始阈值细化,从而克服信号噪声等因素导致的初始阈值周围像素值的误匹配;再次,讨论了适用于2 bit深度像素运动估计的误差度量准则,进而提出了基于模糊量化和2 bit深度像素的运动估计算法;最后,借助信号自相关函数,建立比特深度转换误差—运动向量精度模型来估计该算法所能达到的预测精度。实验结果证明,对于多种类型的视频序列,尤其是场景细节和物体运动比较复杂者,该算法始终能保持较高的估计精度,运动补偿的平均峰值信噪比较之传统2 bit深度像素的运动估计提高0.27 dB。

一种基于混合MELP/CELP的4 kbit/s声码器

利用混合激励线性预测(mixed excitation linear prediction,MELP)算法和码激励线性预测(code excitation linear prediction,CELP)算法的优点,提出了一种混合MELP/CELP语音编码模型。编码端对强浊音帧采用MELP编码,对弱浊音帧和清音帧进行CELP编码。MELP编码器采用相位对齐技术提取强浊音帧的相位参数,解决了合成语音与原始语音在时间上不同步的问题。对实现的4 kbit/s混合MELP/CELP声码器进行客观MOS(mean opinion score)值和主观DRT(diagnostic rhythm test)清晰度测试,结果表明,该声码器的合成语音具有较高的可懂度和清晰度。

无人机航拍视频码率控制算法优化

高效率视频编码(HEVC)在实际应用中很难满足无人机航拍领域的需求。针对此问题,提出一种基于缓冲区状态及视频显著性的码率控制算法。对预处理后的帧进行颜色、纹理特征提取,并采用log-Gabor滤波器对其进行特征滤波,得到当前帧的显著图;计算每帧和每个最小单元(CTU)的显著性权重;以帧的显著性权重和缓冲区状态指导帧层比特分配,以CTU的显著性权重指导CTU层比特分配。实验结果表明,提出的算法可以在缓冲区维持在一个平稳状态的前提下,提高0.61 dB视频显著区域的峰值信噪比,更适用于无人机航拍的场景。

短波通信中的低码率CRC-Polar编译码设计与仿真

针对短波通信中业务传输可靠性高的要求,设计了一种低码率循环冗余校验码(Cyclic Redundancy Check,CRC)级联极化(CRC-Polar)编译码算法。首先给出了基于CRC-Polar编译码的短波通信系统模型及参数,讨论了分段CRC校验、低码率构造与编码算法;其次对打孔、缩短及重复等码率适配方案进行对比分析,并针对性地设计了分段CA-SCL译码算法;最后从不同分段、不同码率适配等角度进行了性能仿真。结果表明,重复码率适配的分段CRC8-Polar码性能最好,优于似然比打孔方案约1dB。此外,在加性高斯白噪声(Additive White Gaussian Noise,AWGN)信道条件下,当数据传输速率为300bit/s、误比特率为10^(-4)时,所需信噪比为-6.4dB,优于美军标188-110C约3.4dB,实现了低信噪比下的可靠传输。

OpenFlow网络中可伸缩视频的自适应传输算法

针对Open Flow网络中的自适应视频传输问题,提出一种可伸缩视频自适应传输算法。在Open Flow网络中,路由器的控制面被分离,由控制器观测可以得到网络的带宽变化。采用自回归模型,根据前一段时间的网络状况预测网络带宽在未来一段时间内的变化情况,控制器根据预测结果决策并告知客户端动态改变请求的视频层数。实验结果表明,该算法在保证较低中断的同时,能够准确地预测网络变化,提高视频播放质量。

More efficient ground truth ROI image coding technique: implementation and wavelet based application analysis

In this paper, more efficient, low-complexity and reliable region of interest （ROI） image codec for compressing smooth low texture remote sensing images is proposed. We explore the efficiency of the modified RO! codec with respect to the selected set of convenient wavelet filters, which is a novel method. Such ROI coding experiment analysis representing low bit rate lossy to high quality lossless reconstruction with timing analysis is useful for improving remote sensing ground truth surveillance efficiency in terms of time and quality. The subjective [i.e. fair, five observer （HVS） evaluations using enhanced 3D picture view Hyper memory display technology] and the objective results revealed that for faster ground truth ROI coding applications, the Symlet-4 adaptation performs better than Biorthogonal 4.4 and Biorthogonal 6.8. However, the discrete Meyer wavelet adaptation is the best solution for delayed ROI image reconstructions.

Edge Oriented Compression Coding on Image Sequence

An edge oriented image sequence coding scheme is presented. On the basis of edge detecting, an image could be divided into the sensitized region and the smooth region. In this scheme, the architecture of sensitized region is approximated with linear type of segments. Then a rectangle belt is constructed for each segment. Finally, the gray value distribution in the region is fitted by normal forms polynomials. The model matching and motion analysis are also based on the architecture of sensitized region. For the smooth region we use the run length scanning and linear approximating. By means of normal forms polynomial fitting and motion prediction by matching, the images are compressed. It is shown through the simulations that the subjective quality of reconstructed picture is excellent at 0.0075 bit per pel.

Study of adaptive modulation and LDPC coding in multicarrier systems

An adaptive modulation （AM） algorithm is proposed and the application of the adapting algorithm together with low-density parity-check （LDPC） codes in multicarrier systems is investigated. The AM algorithm is based on minimizing the average bit error rate （BER） of systems, the combination of AM algorithm and LDPC codes with different code rates （half and three-fourths） are studied. The proposed AM algorithm with that of Fischer et al is compared. Simulation results show that the performance of the proposed AM algorithm is better than that of the Fischer＇s algorithm. The results also show that application of the proposed AM algorithm together with LDPC codes can greatly improve the performance of multicarrier systems. Results also show that the performance of the proposed algorithm is degraded with an increase in code rate when code length is the same.

优化编码树单元级比特分配算法

新一代视频编码标准H.266/VVC(Versatile Video Coding)的码率控制算法采用编码参数相互独立的率失真优化技术。然而,同一帧内的编码树单元(CTU)间在空域上相互影响,且存在全局编码参数;同时,CTU级比特分配公式采用近似的编码参数分配比特,进而降低了码率控制精度和编码性能。针对上述问题,提出空域全局优化CTU级比特分配算法RTE_RC(Rate Control with Recursive Taylor Expansion),并通过递归算法逼近全局编码参数。首先,建立空域全局优化比特分配模型;其次,应用递归算法求解CTU级比特分配模型中的全局拉格朗日乘子;最后,优化编码单元的比特分配并对编码单位进行编码。实验结果表明,在低延时P(Prediction)帧(LDP)配置下,与码率控制算法VTM_RC相比,所提算法的码率控制误差由0.46%下降至0.02%,码率节省了2.48个百分点,编码时间下降了3.52%,显著提升了码率控制精度和率失真性能。

基于对象的水下视频低码率编码算法

由于水下声波信道带宽窄,难以采用高效视频编码(High Efficiency Video Coding,HEVC)实现水下视频低码率传输。提出了一种基于对象的水下视频低码率编码算法。首先对水下对象视频进行时空域下采样以降低其数据量,再采用低延时模式编码少量视频帧作为参考帧。然后,提取水下对象视频非参考帧的特征点,并对特征点和对象掩膜进行编码。在解码端用特征点和掩膜进行对象的粗糙重建,获得对象的初步轮廓和颜色信息。最后,根据粗糙重建对象和参考帧对象的映射关系,采用基于在线学习的方法实现对象的精细重建。实验结果表明,与HEVC相比,所提算法的BDBR-SSIM(Bjontegarrd Delta Bit Rate and Structural Similarity)降低了14.88%。

低码率视频编码的优化方法

采用的低码率视频编码方法是以全局运动补偿和局部运动补偿为核心的混合编码方法.主要针对MPEG-4中原有算法计算量大、复杂度高的特点进行了编码系统优化,将这一编码方法实用化.该优化方法是针对占编码系统70%计算量的全局运动估计进行的,采用了基于运动特征的运动估计方法和鲁棒的目标函数,并在优化方法中引入了三级金字塔的分层计算.从对比实验结果来看,优化方法对不同运动类别视频的编码都是有效的,系统编码速度提高了3倍以上.目前,这项优化方法已经被MPEG-4视频编码优化小组采用.