Real-time and rate–distortion optimized video streaming with TCP

In this paper we explore the use of a new rate–distortion metric for optimizing real-time Internet video streaming with the transmission control protocol (TCP). We lay out the groundwork by developing a simple model that characterizes the expected latency for packets send with TCP-Reno. Subsequently, we develop an analytical model of the expected video distortion at the decoder with respect to the expected latency for TCP, the packetization mechanism, and the error-concealment method used at the decoder. Characterizing the duo protocol/channel more accurately, we obtain a better estimate of the expected distortion and the available channel rate. This better knowledge is exploited with the design of a new algorithm for rate–distortion optimized encoding mode selection for video streaming with TCP. Experimental results for real-time video streaming depict improvement in PSNR in the range of 2 dB over metrics that do not consider the behavior of the transport protocol.     

Perceptual feature guided rate distortion optimization for high efficiency video coding

With the advances in understanding perceptual properties of the human visual system, perceptual video coding, which aims to incorporate human perceptual mechanisms into video coding for maximizing the perceptual coding efficiency, becomes an essential research topic. Since the newest video coding standard—high efficiency video coding (HEVC) does not fully consider the perceptual characteristic of the input video, a perceptual feature guided rate distortion optimization (RDO) method is presented to improve its perceptual coding performance in this paper. In the proposed method, for each coding tree unit, the spatial perceptual feature (i.e., gradient magnitude ratio) and the temporal perceptual feature (i.e., gradient magnitude similarity deviation ratio) are extracted by considering the spatial and temporal perceptual correlations. These perceptual features are then utilized to guide the RDO process by perceptually adjusting the corresponding Lagrangian multiplier. By incorporating the proposed method into the HEVC, extensive simulation results have demonstrated that the proposed approach can significantly improve the perceptual coding performance and obtain better visual quality of the reconstructed video, compared with the original RDO in HEVC.     

AVS插值算法的一种高效的硬件结构设计与实现

提出了AVS解码系统中帧间运动补偿插值算法的一种面向FPGA/ASIC的硬件结构设计.阐述了插值过程的各功能单元的结构,给出了仿真结果及硬件规模.结果表明本文提出的结构设计支持720×576,4:2:0,30FPS的视频在54MHz最低工作频率下的实时解码,是一种适合于集成的高效并行VLSI结构设计.     

机载高清视频处理模块的设计与实现

现代飞机中各种信息传感器的使用越来越广泛,座舱显示系统需要处理的数据也越来越多。为了使飞行员能够认读更多更清晰地视频信息,研究了机载高清视频处理模块的硬件设计和逻辑软件算法。在座舱显示系统中实现了高清视频的显示,包括高清视频的缩放和叠加。满足系统对高清视频处理的要求。     

A two-pass rate control algorithm for H.264/AVC high definition video coding

In this paper, we propose a novel two-pass rate control algorithm to achieve constant quality for H.264/AVC high definition video coding. With the first-pass collected rate and distortion information and the built model of scene complexity, the encoder can determine the expected distortion which could be achieved in the second-pass encoding under the target bit rate. According to the built linear distortion-quantizer (D-Q) model, before encoding one frame, the quantization parameter can be solved to realize constant quality encoding. After encoding one frame, the model parameters will be updated with linear regression method to ensure the prediction accuracy of the quantization parameter of next encoded frame with the same coding type. In order to obtain the expected distortion of each frame under the target bit rate, a GOP-level bit allocation scheme is also designed to adjust the target bit rate of each GOP based on the scene complexity of the GOP in the second-pass encoding. In addition, the effect of scene change on the updating of D-Q model is considered. The model will be re-initialized at the scene change to minimize modeling error. The experimental results show that compared with the latest two-pass rate control algorithm, our proposed algorithm can significantly improve the bit control accuracy at comparable coding performance in terms of constant quality and average PSNR. On average, the improvement of bit control accuracy achieved about 90%.     

A rate-distortion analysis on motion prediction efficiency and mode decision for scalable wavelet video coding

A rate-distortion model for describing the motion prediction efficiency in interframe wavelet video coding is proposed in this paper. Different from the non-scalable video coding, the scalable wavelet video coding needs to operate under multiple bitrate conditions and it has an open-loop structure. The conventional Lagrangian multiplier, which is widely used to solve the rate-distortion optimization problems in video coding, does not fit well into the scalable wavelet structure. In order to find the rate-distortion trade-off due to different bits allocated to motion and textual information, we suggest a motion information gain (MIG) metric to measure the motion prediction efficiency. Based on this metric, a new cost function for mode decision is proposed. Compared with the conventional Lagrangian method, our experiments show that the proposed method is less extraction-bitrate dependent and generally improves both the PSNR performance and the visual quality for the scalability cases.     

SSA optimized digital pre-distorter for compensating non-linear distortion in high power amplifier

Telecommunication Systems - We applied the stochastic salp swarm algorithm (SSA) to design high power amplifier (PA) and digital pre-distorter (DPD) using generalized memory polynomial model. This...     

Algorithm analysis and architecture design for HDTV applications - a look at the H.264/AVC video compressor system

In this article, we suggest some techniques to design the H.264/AVC video coding system for HDTV applications. The design exploration is made according to software profiling. The design considerations of system scheduling and pipelining are discussed followed by the architecture optimization of the significant modules. The efficient H.264/AVC video coding system is achieved by combining these techniques.     

基于Hi3518E的高清网络视频监控系统设计与实现

采用了海思Hi3518E+ OV9712方案,设计并实现了无线网络高清实时监控系统.基于B/S架构,通过移植轻量级网络服务器Boa,实现了客户端Web访问.为了达到实时监控的目的,利用了流媒体技术,在服务器端移植了开源RTP库oRTP,然后利用RTP协议把摄像头采集并且经过编码压缩的H.264码流通过WiFi模块传输到网络上,供客户端实时接收.实验证明,效果理想可靠,完全达到了实时高清监控的要求,对于无线网络监控系统设计具有很大参考价值.     

Efficient FPGA architecture of optimized Haar wavelet transform for image and video processing applications

Multidimensional Systems and Signal Processing - Discrete Wavelet Transform (DWT) is widely used in digital image and video processing due to its various advantages over other similar transform...     

Fast CU size and prediction mode decision method for HEVC encoder based on spatial features

In the high-efficiency video coding (HEVC) standard, intra prediction has higher computational complexity compared with H.264/AVC (advanced video coding) because of increasing the number of intra prediction modes and also higher number of coding unit (CU) sizes. The HEVC encoder evaluates 35 prediction modes on five possible prediction unit (PU) sizes to find the one with the minimum rate–distortion cost. Although this approach improves coding efficiency, it is very time-consuming. In this paper, we propose a fast intra prediction method to reduce the complexity of I-frame coding. The proposed method consists of three stages which is based on smoothness spatial feature. In the first stage, a measure is introduced to estimate CU smoothness by using sum of absolute differences (SAD) among CU pixels in four directions. By considering that a smooth region can be predicted with larger CUs, when the measured smoothness parameter is lower than a predefined threshold, only the prediction modes in the current CU are evaluated. In the second stage, the number of intra prediction modes is reduced based on the calculated SADs in the previous stage. In the last stage, if the first three candidate modes resulted from rough mode decision stage in the previous PU and the current PU are similar, then the best mode prediction of the previous PU is selected as the best candidate mode. Experimental results indicate that the proposed method can reduce the coding time on average to 43 % and maintain coding video quality, whereas bitrate increases negligibly (0.5 %).     

Prediction of transmission distortion for wireless video communication: Algorithm and application

In this paper, we develop algorithms for estimating transmission distortion in wireless video communication systems. By leveraging the analytical results obtained in our previous works, we design low complexity algorithms that are capable of estimating transmission distortion accurately. We also extend our algorithm for pixel-level transmission distortion estimation to pixel-level end-to-end distortion estimation. Furthermore, we apply our pixel-level end-to-end distortion estimation algorithm to prediction mode decision in H.264 encoder. Experimental results show that (1) our transmission distortion estimation algorithm is more accurate and more robust against inaccurate channel estimation than existing distortion estimation algorithms; (2) our mode decision algorithm achieves remarkable PSNR gain over the existing algorithms for prediction mode decision in H.264 encoder, e.g., an average PSNR gain of 1.44 dB for ‘foreman’ sequence when Packet Error Probability (PEP) equals 5%.     

Accelerating QTMT-based CU partition and intra mode decision for versatile video coding

The H.266/VVC achieves about 50% bitrate saving compared to its predecessor H.265/HEVC at the expense of exponentially increased computational complexity. The most efficient but complex technique for H.266/VVC intra frame coding is the QuadTree with a nested Multi-type Tree encoding structure (QTMT), which usually requires traversing the Rate-Distortion (R-D) cost of each partition and each mode for the best option. To alleviate such computational burden while preserving the coding efficiency as much as possible, this paper develops a multi-feature guided Fast CU Partition (FCP) and Laplacian guided Fast Mode Selection (FMS) to accelerate the intra QTMT decision together. For FCP, we regard the CU partition as a classification problem and adopt the Support Vector Machine (SVM) for its low-complexity implementation; after evaluating the contribution of a set of features, three representative features of video textures are selected and used to train the SVM model. Additionally, an advanced technique is applied by adopting a soft decision in SVM for a more flexible trade-off between the complexity and R-D performance. For FMS, we utilize the Laplace operator to determine the most probable directions of the current CU and skip half of the candidate modes for runtime saving. Experimental results demonstrate that the proposed FCP reduces the encoding time of H.266/VVC by 51.03% with 1.65% Bjøntegaard Delta Bit-Rate (BDBR) increase; the proposed FMS reduces the encoding time by 12.68% with 0.09% BDBR loss. Their direct combination and advanced combination finally lead to 54.84% encoding time reduction with 1.74% BDBR increase and 40.39% encoding time reduction with 1.33% BDBR increase, respectively, outperforming state-of-the-art approaches significantly.     

高速高清晰数字摄像机接口原理及应用

在基本的实时数字图像处理方案中,通常是基于数学摄像机,适配卡,PC机平台和操作处理程序组成的固定方式,为实现外加图像处理设备与数字摄像机的连接,解决高速大容量衅像数据直接传输问题,介绍了一种实用方案。     

非压缩高清视频传输系统的部署实现与性能分析

实现了一个非压缩高清视频传输系统,介绍了将此系统部署在中韩国际链路上传输非压缩高清视频的实验情况,测量与分析了系统运行的多种参数,给出了系统性能的评价,并且指出了此系统的应用前景和科研平台价值.     

高清晰低畸变轻小型投影式头盔物镜设计

根据现代化头盔显示系统在像质、畸变和轻小型化方面的高要求,设计了一个视场为62°、出瞳距离为30 mm、出瞳直径为8 mm、采用2.794 cm(1.1")微显示器的折/衍混杂投影式头盔的物镜系统。设计结果表明,系统满足高清晰的XGA的显示模式,其畸变仅为± 0.66%。其质量也仅为62 g,是传统头盔光学系统的1/6,实现了轻小型化。结合投影式头盔显示的其他特点,如物体的正确“闭塞”、深度可感知、多用户的互不干扰等,本设计系统在可视化培训、交互环境、掌中电脑、数字化个兵等领域有重要的应用。     

A rate and distortion analysis of chain codes for line drawings

The performance of chain codes for line drawings in the framework of source coding with a fidelity criterion is investigated. A formal characterization is given for a broad class of chain codes that includes the generalized chain codes of Freeman and the convex quantizers of Koplowitz. Measures of distortion (fidelity) and rate (efficiency) are introduced. The distortion and rate are calculated for several types of chain codes applied to straight and slowly curving lines. Several statistical models for straight lines are introduced and the average performance of chain codes for these models is investigated.     

Exploiting temporal information and adaptive thresholding for fast mode decision in the H264 video coding standard

A new algorithm for fast mode decision in the H264 video coding standard is presented in this paper. The algorithm exploits temporal information and adaptive thresholding and can provide significant computational savings with similar or even better Rate Distortion performance as compared to accepted standard contributions and other techniques found in the literature.     

An improved fast mode decision algorithm for intraprediction in H.264/AVC video coding

In this article, an improved version of one of the most cited intra mode decision algorithms in H.264/AVC video coding is proposed with the aim to improve its efficiency and performance. The reference algorithm determines the interpolation/extrapolation spatial direction (mode) for achieving the best intra prediction using the Sobel gradient calculation. The proposed algorithm suggests reducing the number of gradients calculated and changing the Sobel operator to that of Roberts. In addition to this, it also proposes including the previously encoded neighboring block modes among the evaluated modes. Experimental results show that the proposed algorithm reduces the computational load of the original algorithm and substantially improves its rate-distortion performance.     

可见光通信中高功率效率和低非线性失真算法

实现高功率效率和低非线性失真是无线可见光通信系统中的关键技术之一。近年来正交频分复用(OFDM)调制技术作为一种新型的高速率传输技术被学者广泛而深入的研究。然而,OFDM系统有其固有的缺点,即高PAPR(峰均比),非线性失真和由射频损伤引起的ICI(信道干扰)。在无线可见光通信系统中可见光信号的输出功率是由LED的驱动电流产生的,驱动电流的非线性会导致传输信号存在非线性失真。文中提出一种新的降低PAPR和非线性失真的方法,还提出一种通过自适应信道估计提高SNR(信噪比)进而提高接收端性能的方法。