Seamless switching of scalable video bitstreams for efficient streaming

Efficient adaptation to channel bandwidth is broadly required for effective streaming video over the Internet. To address this requirement, a novel seamless switching scheme among scalable video bitstreams is proposed in this paper. It can significantly improve the performance of video streaming over a broad range of bit rates by fully taking advantage of both the high coding efficiency of nonscalable bitstreams and the flexibility of scalable bitstreams, where small channel bandwidth fluctuations are accommodated by the scalability of a single scalable bitstream, whereas large channel bandwidth fluctuations are tolerated by flexible switching between different scalable bitstreams. Two main techniques for switching between video bitstreams are proposed. Firstly, a novel coding scheme is proposed to enable drift-free switching at any frame from the current scalable bitstream to one operated at lower rates without sending any overhead bits. Secondly, a switching-frame coding scheme is proposed to greatly reduce the number of extra bits needed for switching from the current scalable bitstream to one operated at higher rates. Compared with existing approaches, such as switching between nonscalable bitstreams and streaming with a single scalable bitstream, our experimental results clearly show that the proposed scheme brings higher efficiency and more flexibility in video streaming.     

Distributed video coding based on part intracoding and soft side information estimation

Recently, distributed source coding (DSC) has been proposed to implement source compression by exploiting source statistics at the decoder only, which enables low-complexity video coding. However, to date, the video codecs based on DSC have been unable to compress as efficiently as traditional predictive video codecs, such as H.264. So, new techniques have to be investigated to improve the performance of the distributed video coding scheme for practical applications. In this paper, I propose a novel distributed video coding scheme based on part intracoding and soft side information estimation. Firstly, at the encoder side, to improve the compression performance of distributed video coding system, we divide the video data into strongly correlative data encoded by Slepian–Wolf codec and weakly correlative data encoded by Intracoding codec. Secondly, at the decoder side, to improve the accuracy of side information estimation, a soft side information estimation method is proposed, which is more suitable for video coding due to the non-stationary feature of video data. Our experimental results show that the performance of our coding system is better than that of the traditional distributed video coding system while keeping the simple encoding property. Also the concept of soft side information is a new idea in distributed video coding and will significantly influence the side information estimation method.

H．264／AVC解码器优化的研究

视频编码新标准H．264／AVC与先前的标准如MPEG2、H．263、MPEG4第2部分相比，虽具有更高的编码效率和差错鲁棒性，但是这些编码效率的提高是以增加编码器和解码器的复杂度为代价的。研究表明，由于H．264／AVC编解码器的计算复杂度比其他视频压缩标准高出几倍甚至十几倍，因此实现实时编解码器需要寻找高效的优化方法。为了对解码器进行优化，从软件和硬件平台的角度提出了一种解码器的优化方法，最后进行了实验，实验结果显示，优化后的软件解码器能够达到实时解码。     

Hybrid linear weighted prediction and intra block copy based light field image coding

Light field imaging can capture both spatial and angular information of a 3D scene and is considered as a prospective acquisition and display solution to supply a more natural and fatigue-free 3D visualization. However, one problem that occupies an important position to deal with the light field data is the sheer size of data volume. In this context, efficient coding schemes for this particular type of image are needed. In this paper, we propose a hybrid linear weighted prediction and intra block copy based light field image codec architecture based on high efficiency video coding screen content coding extensions (HEVC SCC) standard to effectively compress the light field image data. In order to improve the prediction accuracy, a linear weighted prediction method is integrated into HEVC SCC standard, where a locally correction weighted based method is used to derive the weight coefficient vector. However, for the non-homogenous texture area, a best match in linear weighted prediction method does not necessarily lead to a good prediction of the coding block. In order to alleviate such shortcoming, the proposed hybrid codec architecture explores the idea of using the intra block copy scheme to find the best prediction of the coding block based on rate-distortion optimization. For the reason that the used “try all then select best” intra mode decision method is time-consuming, we further propose a fast mode decision scheme for the hybrid codec architecture to reduce the computation complexity. Experimental results demonstrate the advantage of the proposed hybrid codec architecture in terms of different quality metrics as well as the visual quality of views rendered from decompressed light field content, compared to the HEVC intra-prediction method and several other prediction methods in this field.     

A pretreatment to improve the quality metrics performance for encoding H264/AVC

The study of the human visual system is very interesting to quantify the quality of an image or to predict perceived information. The contrast sensitivity function is one of the main ways to incorporate the human visual system properties in an imaging system. It characterizes its sensitivity to spatial frequencies. In this paper, we are interested in establishing a pretreatment for existing metrics with full reference (“peak signal‐to‐noise ratio”, “digital video quality”) for the H.264/MPEG‐4 (Motion Picture Expert Group) advanced video coding standard. We realize in our algorithm the FFT transformation to apply the contrast sensitivity function. Our method is applicable to any size of image and video sequence by increasing its size at powers of two. This increase is achieved by adding “mirror image.” We evaluate the performance of the proposed pretreatment by using subjective “LIVE” video databases. The performance metrics, that is, Pearson (PLCC), Spearman correlation coefficients (SROCC) and root mean square prediction error (RMSE) indicate that the proposed method gives a good performance in H264 codec distortions.     

基于DCT频域条件帧间补偿法的视频编码方案及其实现

运动图象的压缩是实现多媒体通信的关键技术之一。本文提出一种基于离散余弦变换系数的条件帧间补偿法及其视频编码方案。该算法利用DCT变换特点和人眼视觉特性，快速高效地对运动图象进行编码。     

基于 DCT 频域条件帧间补偿法的视频编码方案及其实现

运动图象的压缩是实现多媒体通信的关键技术之一。本文提出一种基于离散余弦变换（ＤＣＴ）系数的条件帧间补偿法及其视频编码方案。该算法利用ＤＣＴ变换的特点和人眼视觉特性，快速高效地对运动图象进行编码。由于运算量低，该算法可以在ＰＣ机上用软件实时实现，适用于基于ＰＣ平台的可视电话、会议电视和可视多媒体通信系统。     

Efficient MPEG compressed video analysis using macroblock typeinformation

Efficient indexing methods are required to handle the rapidly increasing amount of visual information within video databases. Video analysis that partitions the video into clips or extracts interesting frames is an important preprocessing step for video indexing. We develop a novel method for video analysis using the macroblock (MB) type information of MPEG compressed video bitstreams. This method exploits the comparison operations performed in the motion estimation procedure, which results in specific characteristics of the MB type information when scene changes occur or some special effects are applied. Only a simple analysis on MB types of frames is needed to achieve very fast scene change, gradual transition, flashlight, and caption detection. The advantages of this novel approach are its direct extraction from the MPEG bitstreams after VLC decoding, very low complexity analysis, frame-based detection accuracy and high sensitivity     

MPEG音频现状及其发展研究

多媒体应用需求的增长使得MPEG标难的发展已超越了过去单一视听媒体编码的范畴．根据音频信息的应用特点分析了MPEG音频标难，从特征表示、内容描述到互操作应用框架形成的技术发展过程，介绍了不同阶段制定的MPEG音频标难的主要技术和应用特点，并说明在新应用需求和新目标出现的同时，更高效的编码方法和更精确的描述手段仍然是当前考虑的重点．提出和讨论了对MPEG音频做进一步研究中需要解决的若干技术问题及今后的研究方向。     

基于分布式编码的多描述视频编解码器

为了解决多描述视频编码器在丢包信道下的漂移问题,本文提出了一种新的基于分布式视频算法的多描述视频编码方案。实验结果表明,借助于分布式编码的稳健性,这一新方案能有效地避免漂移问题。为了解决多描述视频编码器在丢包信道下的漂移问题,提出了一种新的基于分布式视频算法的多描述视频编码方案。实验结果表明,借助于分布式编码的稳健性,这一新方案能有效地避免漂移问题。     

数据驱动的并行视频编码器的设计和实现(英文)

通用视频编码系统一般基于标准视频压缩算法, 比如 MPEG4 和 H.264。但这些标准算法包括如离散余弦变换和运动估计等高复杂度的计算,所以为了实现实时通信,编码系统通常采用以硬件为基础的实现方法。然而以硬件为基础的视频编码系统具有实施周期长、成本高、灵活性差等不足。文章介绍了一种基于低计算复杂度自适应块截短编码方案的数据驱动并行视频编码系统,实验结果验证了编码系统的有效性。     

Content-based scalable H.263 video coding for road traffic monitoring

For sending video data through very low bit-rate mobile channels, video codec with high compression rate is the pre-requisite. Although the H.263 video codec is recommended as one of the candidates due to its simplicity and efficiency, it is generally believed that its compression efficiency can be further improved if the content-based scalable video coding technique can be applied. In this paper, we propose a modified H.263 encoder which supports real-time content-based scalable video coding. The proposed technique is applied to real-time video surveillance systems for road traffic monitoring. For the proposed approach, the moving objects, i.e. cars, are first extracted from the steady background. Their activities are then further classified as fast or slow by assessing the regularity of their motion. The information is then passed to a modified H.263 encoder to reduce the temporal and spatial redundancies in the video. As compared with the conventional H.263 encoder using for the same application, the proposed system has a 20% increase in compression rate with negligible visual distortion. The proposed system fully complies with the ITU H.263 standard hence the encoded bit stream is completely comprehensible to the conventional H.263 decoder.     

基于OMAP的视频监控系统关键技术研究

随着监控技术的不断发展,嵌入式视频监控系统以其占用资源少、构建灵活以及很强的扩展性得到了越来越多的应用。文中以实现实时视频监控为目的,研究了视频传输中的几项关键技术。基于TI的OMAP4430平台,充分利用其多核特性,介绍了一种基于H.264的远程视频监控系统设计方案,采用H.264的视频编解码方法比MPEG系列能够提供更高的压缩率,在很大程度上增大了带宽的利用率。在此基础上,分析了RTP/RTCP协议在视频传输中的关键参数、RTP封装等几项关键技术,并最终实现了视频的实时传输。实验结果表明该方案传输性能良好,有较高的可靠性。     

MPEG Video Encryption Algorithms

Multimedia data security is important for multimedia commerce. Previous cryptography studies have focused on text data. The encryption algorithms developed to secure text data may not be suitable to multimedia applications because of the large data size and real time constraint. For multimedia applications, light weight encryption algorithms are attractive.We present four fast MPEG video encryption algorithms. These algorithms use a secret key to randomly change the sign bits of Discrete Cosine Transform (DCT) coefficients and/or the sign bits of motion vectors. The encryption is accomplished by the inverse DCT (IDCT) during the MPEG video decompression processing. These algorithms add a small overhead to MPEG codec. Software implementations are fast enough to meet the real time requirement of MPEG video applications. The experimental results show that these algorithms achieve satisfactory results. They can be used to secure video-on-demand, video conferencing, and video email applications.     

A reduced reference video quality assessment of H.264 and mpeg2 codec based on sharpness metric

In this paper, we propose a new perceptually significant video quality metric for the H.264/Motion Picture Expert Group (MPEG)‐4 Advanced Video Coding (AVC) and MPEG2 standard. Our method operates in the spatial domain by using the Sobel filter. The proposed approach does not require a high computational complexity and can be suitable for real‐time evaluation. We evaluate the performance of the proposed method by using three Common Intermediate Format sequences at different compression rates. The comparison of the obtained results is made with some video quality models using “LIVE”, “IVP” and “IRCCyN/IVC 1080i” databases. The performance metrics, i.e. Pearson and Spearman correlation coefficients, indicate that the proposed method gives a good performance in H264 and MPEG2 codec distortions with the three databases comparing with other models.     

Motion Flow-Based Video Retrieval

In this paper, we propose the use of motion vectors embedded in MPEG bitstreams to generate so-called ldquomotion flowsrdquo, which are applied to perform video retrieval. By using the motion vectors directly, we do not need to consider the shape of a moving object and its corresponding trajectory. Instead, we simply ldquolinkrdquo the local motion vectors across consecutive video frames to form motion flows, which are then recorded and stored in a video database. In the video retrieval phase, we propose a new matching strategy to execute the video retrieval task. Motions that do not belong to the mainstream motion flows are filtered out by our proposed algorithm. The retrieval process can be triggered by query-by-sketch or query-by-example. The experiment results show that our method is indeed superb in the video retrieval process.     

A region-based H.263+ codec and its rate control for low VBR video

This paper presents a region-based video codec, which is compatible with the H.263+ standard, and its associated rate control algorithm for low variable-bit-rate (VBR) video. The proposed region-based coding scheme is a hybrid method that incorporates traditional block DCT coding as well as object-based coding. To achieve this, we adopt H.263+ as the platform, and develop a fast macroblock-based segmentation method to implement the new region-based codec. The associated rate control solution includes rate control in three levels: encoding frame selection, frame-layer rate control and macroblock-layer rate control. The goal is to improve human visual perceptual quality at low bit rates. The efficiency of the proposed rate control algorithm applied to the region-based H.263+ codec is demonstrated via several typical test sequences.     

基于多DSP的MPEG 2高速视频压缩系统设计与实现

介绍了一种高速视频采集压缩系统的实现.该方案能够采集camera link 摄像机视频信号或制式为PAL的视频信号;对采样后的数字视频数据用四个DSP(TI C6416)进行实时压缩处理并存储记录.数据压缩采用视频压缩标准MPEG-2;处理速度达到75 fps(720×576灰度图像).     

MPEG格式视频流的倒序播放技术与实现

简要讨论了当前流行的MPEG视频数据的编码方式。根据MPEG视频流的帧重建技术的思想,使用Windows系统中与显示设备内存属性相同的系统内存缓冲区进行帧图像的重建,成功地实现了MPEG视频流以任意速度进行倒序播放。实验结果 表明了该方法的有效性。