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.

ZTE IPTV Low Bit Rate High Definition Transcoding Solution Nominated for Global IPTV Industry Award

ZTE Corporation announced on 1 March that its innovative IPTVlowbitrate highdefinition transcoding solution has been nominated for the World＇s Best Component or Enabler Award by the IPTV World Forum. The ZTE solution is on display at the Mobile World Congress 2012 （MWC 2012） in Barcelona.

An Improved SPIHT Algorithm for Image Compression in Low Bit Rate

Aiming at shortage of the SPIHT algorithm, an improved image compression algorithm is proposed, in order to overcome the shortcomings of decoding image quality and coding time, LS9/7 lifting wavelet transform is adopted. According to the characteristics of the human visual system (HVS), the scanning mode and the method to determine the threshold of algorithm are changed to improve the quality of reconstruction image. On the question of repeating scan of SPIHT algorithm, using maximum list thought, greatly reduce the computation and save operating time. The experimental results have proved that the improved algorithm of image decoding time and the quality of reconstruction images are better than the original algorithm , especially in the case of low bit rate.

Study of low bit rate speech codec algorithm in underwater acoustic communication

At medium or long distance （〉 10 kin） underwater acoustic speech communication, information transfer rate is constrained by the complicated, time varying channel and limited bandwidth. The bit rate of speech coding is required to be as low as possible. The time delay of underwater acoustic wave propagation can be used for low bit rate speech coding. After investigating the Mixed Excitation Linear Prediction （MELP） standard and taking account of the auditory perceptual features, a variable and adjustable bit rate speech codec algorithm has been proposed, whose average bit rate is about 600 bps. The average Perceptual Evaluation of Speech Quality Mean Opinion Score （PESQ MOS） of synthesized speeches is about 2.8. It has been proved by the computer simulation and sea trial that the performance of the proposed algorithm is well and robust when bit error rate is no more than 10-3. The synthesized speech is vivid and intelligible, and keeps main individual characteristics of speaker.

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.

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.

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.

基于尺度特征融合的极低比特率三维复杂图像无损压缩

由于三维复杂图像具有高维度和大规模的特点,且极低比特率下容易导致细节丢失和失真增强,使得三维复杂图像的编码较为复杂。因此,提出基于尺度特征融合的极低比特率三维复杂图像无损压缩方法。利用各向异性扩散与垂直扩散处理三维复杂图像,增强图像边缘信息。采用四叉树算法,建立自适应分块机制,按照图像细节复杂程度划分多个图像块。构建残差网络、反卷积网络结构的残差变换模块,融合图像多尺度特征,输出压缩图像。引入高分辨率累加器和计数器,实现压缩图像无损编码,实现完整的三维复杂图像无损压缩。实验结果表明:应用基于尺度特征融合的新型无损压缩方法后,图像压缩重构结果的信息熵达到了30,实现了压缩图像质量的提升。

基于DVB-S2X协议的低轨卫星通信性能仿真分析

介绍了DVB-S2X标准,重点分析了其中高阶调制技术的基本原理和星座映射,在进行星地链路分析的基础上,构建了DVB-S2X标准低轨卫星通信仿真模型,针对DVB-S2X标准中16APSK、32APSK、64APSK调制信号开展仿真试验,以误码率和丢帧率为指标进行通信性能分析。

语义引导的水下带噪语音通信

针对狭窄带宽的多径水声信道和信源噪声干扰导致的退化语音,提出了一种语义引导的水下带噪语音通信系统,实现了噪声环境下高效鲁棒的语音通信。首先,通过引入语音去噪网络降低了信源噪声的影响。系统通过传输语音的语义信息,实现了语音信号的极限压缩。针对信道噪声对数据的损伤,使用语义纠错模块在接收端对退化的语义特征进纠错,从而提高重建语音的可理解性。此外,结合多阶段训练策略的退化知情模型进一步增强所提方法在水声信道中的鲁棒性和泛化性。最后,在语音重建过程中使用多感受野-挤压激励融合模块以捕获语义特征中的全局语义信息,优化重建语音的可理解性。仿真实验结果表明,该方法在极低码率压缩的情况下,在复杂的噪声环境和不同的水声信道条件中,具有良好的重建性能。

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。

基于增强型多尺度残差生成对抗网络的图像压缩

为解决低码率下更符合人类视觉感知的图像压缩,提出一种基于增强型多尺度残差生成对抗网络的有损压缩方法。在网络框架的自动编码器中,使用一种结构上改进的增强型多尺度残差块,其可以扩大感受野,更容易获得图像的全局信息。引入简易注意力模块,帮助网络更加关注图像复杂的部分,减少简单部分的比特。判别器部分采用全新的相对平均判别器,在网络框架中使用LPIPS(learned perceptual image patch similarity)感知损失减轻图像伪影问题。采用两阶段训练的方式解决引入生成对抗网络导致训练不稳定的问题。实验结果表明了在低码率下所提模型的有效性,与之前的工作相比,所提方法在感知失真指标上表现更优,性能提升了65%左右,重建图像更符合人类视觉感知。

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。

基于多特征融合和BiLSTM的语音隐写检测算法

针对传统互联网低比特率编解码器(internet Low Bit Rate Codec,iLBC)语音隐写主要集中在线性频谱频率系数矢量量化、码本搜索矢量量化或增益量化的单个阶段,难以应对多阶段下的联合隐写检测等问题,提出一种基于多特征融合和双向长短时记忆(Bi-Directional Long Short-Term Memory,BiLSTM)网络的iLBC语音隐写检测算法.通过分析隐写对不同阶段参数带来的影响,提取线性频谱频率系数矢量量化、码本搜索矢量量化和增益量化过程中的多种隐写特征,并分别输入到相应的BiLSTM检测网络,最后将各检测网络的结果进行融合,得到最终隐写检测结果 .实验表明,所提算法可以实现多阶段下的联合隐写检测,而且在语音时长较短时,仍能取得优异的检测结果,平均检测准确率达到了90%以上.

信息跳时架构下分层捷变低截获概率通信波形

针对周期信号抗破译性能较差及非周期聚敛性带来的误码性能下降的问题,本文提出一种时宽-信息跳时-调频率分层波形架构。通过构建信息跳时,掩护时宽随机化的模式,解决了误码性能变时宽下降问题,加强了波形的低截获概率特征。本文以数学推导和仿真分析的方法,探究了此分层波形架构下的误码性能、功率谱类噪声性能、二次谱域周期聚敛性及先验信息抗破译性。理论分析和仿真验证表明:时宽-信息跳时-调频率分层波形可以保证与定时宽信号相比,在不降低误码性能的条件下,降低了波形的周期聚敛性,从而提高了波形的截获概率性能。

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%。

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H.264低比特率视频流的半脆弱盲水印算法实现

本文提出一种基于H·264低比特率视频流的半脆弱盲水印方法,通过在H·264特有的的帧内预测和运动向量预测中分别嵌入鲁棒水印和脆弱水印,达到版权保护和内容完整性认证的双重目的.通过在嵌入强度和预测模式选择的拉格朗日乘子中引入H·264量化因子,增强了水印对重量化编码的抵抗力,取得更好的率失真平衡,减小水印嵌入对视频流比特率的影响.该算法可以实现水印的快速嵌入提取,满足视频实时处理的要求,实验结果证明了该算法的有效性.

一种基于基音预测的信息隐藏算法

针对低速率语音编码问题,提出一种基于基音预测的信息隐藏算法。在基音预测编码过程中,采用控制基音闭环搜索的自适应码本搜索范围方法,实现秘密信息的嵌入,在进行语音压缩的同时完成信息隐藏。实验结果证明,该算法具有良好的隐蔽性,且计算复杂度较低。在编码标准G.729a中,秘密比特信息嵌入速率统计平均最高可达374.636 bit/s,PESQ恶化改变率在10.4%以内,检测正确率在66%左右。

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.