VBR视频流多重分形建模

该文在小波域多重分形基础上,研究了基于分布、点集(PM)分布的多重分形小波模型(MWM)的性能,并提出了一种具有更好的逼近性能的混合PM-分布形式;同时,针对VBR视频流的I,P,B帧周期分布特性,充分利用异种帧相关性,建立了考虑帧间相关性的混合多重分形小波VBR视频流量模型CMWM(Composite MWM)。仿真试验表明,与传统的短相关和长相关模型相比,具有多重分形特性的CMWM能更加精确地描述MPEG视频业务的统计特性和排队性能。     

An extended discrete autoregressive model for variable bit rate video traffic encoded by scalable video codec

Designing an effective and high performance network requires accurate characterization and modeling of network traffic. This paper provides a study of the transmission, modeling, and analysis of variable bit rate (VBR) video, which is fundamental for designing protocols and for effective utilization of networks in video transmission. To meet the specified requirements of future networks, the scalable video codec (SVC) was chosen as the video compression standard. The main objective of this work was to propose a statistical model that will allow better coordination between generated SVC video traffic and original video traffic. The performance of the proposed model was evaluated by comparing the model with three existing low‐complex statistical models using graphical and statistical measurements as well as cross‐validation. For all evaluation techniques, the accuracy of the proposed model was evaluated, and the frame size distribution of the modeled traffic was found to match that of the original video traffic better than other existing models. Copyright © 2015 John Wiley & Sons, Ltd.     

Modeling one- and two-layer variable bit rate video

This paper presents a source model for VBR video traffic. A finite-state Markov chain is shown to accurately model one- and two-layer video of all activity levels on a per source basis. Our model captures the source dynamics, including the short-term correlations essential for studying network performance. The modeling technique is shown to be applicable for both H.261 and MPEG2 encoded video of a variety of activity levels. The traffic model is shown in a simulation study to be able to accurately characterize both the single-source buffer occupancy over a wide range of buffer sizes and the multiplexing behavior. The VBR video model is also used to model the enhancement layer of two-layer SNR scalable video. We show that two-layer encoding has significantly better statistical multiplexing gains than one-layer video, particularly when the network admits calls based on a leaky-bucket characterization     

SIMULATION AND MODELLING OF VARIABLE BIT RATE MPEG VIDEO TRANSMISSION OVER ATM NETWORKS

This paper proposes an efficient transmission mechanism based on frame spreading, for variable bit rate (VBR) MPEG compressed video, through an asynchronous transfer mode (ATM) multiplexer, such as a cable head-end. We implement a priority scheme in a software MPEG encoder which produces proportionate traffic in both (i.e. high and low) priority partitions for all three types of video frames used in MPEG, i.e. intraframe (I), predicted (P) and bidirectionally interpolated (B). Furthermore, we simulate an ATM multiplexing scheme with a pushout buffer mechanism providing priority scheduling at the multiplexer for the two video partitions. We load the multiplexer with VBR MPEG traffic and collect performance statistics such as the cell loss ratios for various frame spreading scenarios. In order to study the transmission mechanisms via simulation, we develop two statistical models, using the transform-expand-sample technique (TES) for VBR MPEG video with two levels of priority. The first model is matched with the empirical histogram and autocorrelation function of each frame type (I, P and B). The second model is created with the assumption of a gamma distribution for the number of bits in each frame type. We conduct experiments using both models and compare the results.     

基于小波支持向量机的VBR视频流量预测

：VBR视频流量具有时变性、突发性和非线性等变化特点,为了提高VBR视频流量的预测精度,提出一种小波支持向量机的VBR视频流量预测模型(WSVM)。首先对VBR视频流量时间序列进行相空间重构,然后将其输入到小波支持向量机进行学习,建立VBR视频流量预测模型,最后采用仿真实验对模型性能进行测试,并与支持向量机、小波神经网络进行对比。仿真结果表明,相对于其它预测模型,WSVM模型提高了VBR视频流量预测精度,能够更加准确反映VBR视频流量的复杂变化规律。     

Study of the impact of MPEG-1 correlations on video-sourcesstatistical multiplexing

Variable bit-rate (VBR) video is expected to become increasingly important with the large scale deployment of broadband-integrated services networks (B-ISDNs). While the modeling of VBR video sources has received significant attention, there is no widely accepted model which lends itself to mathematical analysis. Furthermore, new video compression standards are emerging, such as the MPEG family. A detailed statistical analysis of a long sample of a movie encoded with an MPEG-1 algorithm highlights that traffic generated by an MPEG-1 encoder has both a high degree of burstiness (peak/average ratio greater than five) and a strong long-term correlation (positive correlation lasts for ten/twenty minutes). In this paper, we propose and analyze a Markov model which captures both the burstiness and the temporal dependencies of MPEG traffic. Furthermore, we show that our model is a flexible traffic generator which is suitable for studying statistical multiplexing issues. Specifically, we study both the multiplexing of a VBR video source with low priority traffic and the multiplexing of several VBR video sources. The results obtained show that the long-term correlation significantly affects the tail of the delay distribution even for lightly loaded networks. The presence of a long range dependence in the MPEG traffic significantly reduces the gain in terms of network utilization which can be achieved with statistical multiplexing of i.i.d. sources     

Quality-optimised MPEG2 video data rate control using fuzzy logictechniques

Fuzzy logic control has been employed to improve the rate control mechanism for a MPEG2 video encoder. The data rate of compressed video is controlled by video encoders for either variable bit rate (VBR) or constant bit rate (CBR) applications. In VBR video transmission, it is considered to be more efficient to regulate the video rate by the video coder than by network management in order to avoid network congestion and maintain stable video quality. This rationale can also be applied to CBR transmission. Two fuzzy-logic-based rate control techniques are proposed which maintain the buffer occupancy within a specified range. In the proposed technique for VBR applications, a video quality measure is taken as the crucial control parameter. In CBR rate control, the video data rate or the buffer occupancy is also considered as a fuzzy logic variable. Proposed techniques are designed to control either data rate or video quality, depending on the mode of transmission, i.e. CBR or VBR for the MPEG2 encoder. The performance is compared to a typical VBR MPEG video coder with fixed quantiser step sizes for VBR and also to the CBR video coder with MPEG2 TM5 at typical channel rates. Simulation results are presented with peak signal-to-noise ratio, data rate variation and buffer occupancy as the performance measures     

考虑异种帧相关性的VBR MPEG视频源混合回归模型

ＭＰＥＧ作为一种国际动态图像压缩标准,其越来越广泛。为在通信网络上有效地传输和控制ＭＰＥＧ可变经特率（ＶＢＲ）数据流,第一个关键问题就是如何建立它的统计模型,目前已有的视频源模型都没有考虑不同类型帧之间的相关性,并不能很好地模拟ＶＢＲＭＰＥＧ视频源。本文首次提出了一咋处世划种帧相关性的ＶＢＲＭＰＥＧ视频源统计模型,混合回归（ＣＲ）模型,及其参数估计算法,实验结果表明,和传统的自回归（ＡＲ）模型相比     

突发业务流的TES建模方法

高速通信网络存在大量诸如可变速率(VBR)视频这类具有突发性的业务流。突发性,在数学上主要通过业务流的到达时间间隔的边缘概率分布和自相关函数来描述。TES(Transform-Expand-Sample)是一种建模静态随机过程的非参数化技术,能准确匹配边缘概率分布并很好地近似自相关函数。本文简要介绍了TES方法的基本原理,再详细讨论突发业务流的TES建模及其软件实现。对MPEG视频业务的建模的仿真结果表明,TES模型能够很好地表征网络业务流的突发性。     

Deterministic delay bounds for VBR video in packet-switchingnetworks: fundamental limits and practical trade-offs

Compressed digital video is one of the most important traffic types in future integrated services networks. However, a network service that supports delay-sensitive video imposes many problems since compressed video sources are variable bit rate (VBR) with a high degree of burstiness. In this paper, we consider a network service that can provide deterministic guarantees on the minimum throughput and the maximum delay of VBR video traffic. A common belief is that due to the burstiness of VBR traffic, such a service will not be efficient and will necessarily result in low network utilization. We investigate the fundamental limits and trade-offs in providing deterministic performance guarantees to video and use a set of 10 to 30 min. long MPEG-compressed video traces for evaluation. Contrary to conventional wisdom, we are able to show that, in many cases, a deterministic service can be provided to video traffic while maintaining a reasonable level of network utilization. We first consider an ideal network environment that employs the most accurate deterministic, time-invariant video traffic characterizations, the optimal earliest-deadline-first packet schedulers, and exact admission control conditions. The utilization achievable in this situation provides the fundamental limits of a deterministic service. We then investigate the utilization limits in a network environment that takes into account practical constraints, such as the need for simple and efficient policing mechanisms, packet scheduling algorithms, and admission control tests     

Smoothing and transporting video in QoS IP networks

Real‐time traffic such as voice and video, when transported over the Internet, demand stringent quality of service (QoS) requirements. The current Internet as of today is still used as a best effort environment with no quality guarantees. An IP‐based Internet that supports different QoS requirements for different applications has been evolving for the past few years. Video streams are bursty in nature due to the instant variability of the video content being encoded. To help mitigate the transport of bursty video streams with minimal loss of information, rate‐adaptive shapers (RASs) are usually being used to reduce the burstiness and therefore help preserve the desired quality. When transporting video over a QoS IP network, each stream is classified under a specific traffic profile to which it must conform, to avoid packet loss and picture quality degradation. In this paper we study, evaluate and propose RASs for the transport of video over a QoS IP network. We utilize the encoding video parameters for choosing the appropriate configuration needed to support the real‐time transport of Variable Bit Rate (VBR) encoded video streams. The performance evaluation of the different RASs is based on the transport of MPEG‐4 video streams encoded as VBR. The performance is studied based on looking at the effect of various parameters associated with the RASs on the effectiveness of smoothing out the burstiness of video and minimizing the probability of packet loss. Copyright © 2005 John Wiley & Sons, Ltd.     

A new approach to long‐range dependence in variable bit rate video traffic

Recently it has been observed that variable bit rate (VBR) video traffic displays long‐range dependence, which suggests that traditional Markovian models may not be suitable for performance evaluation of telecommunications networks carrying this traffic. Inspection of the bit rate profile of VBR video traffic suggests that shifting level processes might be more appropriate for this task. In this paper we show that a particular class of these processes matches the autocorrelation and bit rate distribution of real VBR video traffic, including exhibiting long‐range dependent behaviour. This revised version was published online in June 2006 with corrections to the Cover Date.     

A bandwidth assignment algorithm on a satellite channel for VBR traffic

Variable bit rate (VBR) video is currently by far the most interesting and challenging real-time application. A VBR encoder attempts to keep the quality of video output constant and at the same time reduces bandwidth requirements, since only a minimum amount of information has to be transferred. On the other hand, as VBR video traffic is both highly variable and delay-sensitive, high-speed networks (e.g. ATM) are generally implemented by assigning peak rate bandwidths to VBR video applications. This approach may, however, be inefficient in a satellite network based on a TDMA scheme. To overcome this problem, we have designed a demand assignment satellite bandwidth allocation algorithm in TDMA, named V2L-DA (VBR 2-Level Demand Assignment), which manages the VBR video traffic according to a dynamic bandwidth allocation algorithm. In this paper we discuss how to tune the proposed algorithm in order to optimize network utilization when MPEG-1 VBR video traffic is being transmitted. Our results indicate that most of the time only 40% of the peak rate bandwidth is needed to satisfy the VBR source, so the remaining 60% of the peak rate bandwidth can be used to transmit the datagram traffic queued in the network stations. © 1997 John Wiley & Sons, Ltd.     

Implementation of SDTV Video Encoder with Real-Time Constant and Variable Bit-Rate Control

The digital standard definition television (SDTV) encoder is a very important part of the digital TV broadcast chain. Most real-time MPEG-2 encoders are designed to perform in a constant bit-rate (CBR) mode. But an even better compressed stream can be created by employing a variable bit-rate (VBR) encoding algorithm. VBR can be exploited as a means of achieving statistical multiplexing for digital broadcast satellites. This paper suggests an implementation procedure of an SDTV video encoder and proposes a novel VBR bit-allocation strategy that could be implemented in this encoder system. First, using a rate-quantization model and rate-quantization perceptual model, a real-time VBR bit-allocation strategy is deduced. In this strategy, more (or fewer) bits are allocated to "difficult-to-encode" (or "easy-to-encode") groups of pictures (GOPs), which are distinguished according to the estimated encoding complexity of the GOPs. After allocating an appropriate number of bits to each GOP by using this VBR bit-allocation strategy, we use a CBR rate control algorithm to allocate a number of bits and select a quantization scaler for each picture of a GOP. Then smooth visual quality is achieved not only in a GOP but also in the whole video sequence. Second, the system implementation of an SDTV video encoder including a video input module, a video encoding module, a system control and rate control module (SCRCM), and a PES packetizing module is described. We also discuss in detail how to implement our real-time VBR bit-allocation strategy in the SCRCM. Finally, experimental results demonstrate that our proposed VBR encoder displays a better performance than the CBR encoder.     

VBR video: tradeoffs and potentials

The authors examine the transport and storage of video compressed with a variable bit rate (VBR). They focus primarily on networked video, although they also briefly consider other applications of VBR video, including satellite transmission (channel sharing), playback of stored video, and wireless transport. Packet video research requires careful integration between the network and the video systems; however, a major stumbling block has resulted because commonly used terms are often interpreted differently by the video and networking communities. The paper then, has two main goals: (i) to clarify the definitions of terms that are often used with different meaning by networking and video-coding researchers and (ii) to explore the tradeoffs entailed by each of the various modalities of VBR transmission (unconstrained, shaped, constrained, and feedback). In particular, they evaluate the tradeoff among the advantages (better video quality, less delay, and more calls) that were identified by early proponents of VBR video transmission. An underlying theme of this paper is that increased interaction between the video and network design has potential for improving overall decoded video quality without changing the network capacity     

Real-time VBR video traffic prediction for dynamic bandwidth allocation

In this paper, we systematically investigate the long-term, online, real-time variable-bit-rate (VBR) video traffic prediction, which is the key and complicated component for advanced predictive dynamic bandwidth control and allocation framework for the future networks and Internet multimedia services. We focus on neural network-based approach for traffic prediction and demonstrate that the prediction performance and robustness of neural network predictors can be significantly improved through multiresolution learning. We show that neural network traffic predictor trained through the multiresolution learning (called multiresolution learning NN traffic predictor) can successfully predict various real-world VBR video traffic up to hundreds of frames in advance, which then lays a solid foundation for predictive dynamic bandwidth control and allocation mechanism. Also, dynamic bandwidth control/allocation based on long-term traffic prediction is discussed in detail.     

支持变速率视频流传输的重协商优化算法

针对变速率视频流在多个时间尺度上突发的性质,本文提出了基于多级整形和多时间尺度带宽分配与准入的重协商优化算法.算法通过视频源与边缘网关的重协商过程,对进入网络的数据流进行包络,提高数据流的控制性和预测性,从而减少突发对网络所造成的破坏;并且对中小规模的数据流复合的情况,可以取得接近VBR流的复用增益.     

Dynamic bandwidth allocation for interactive applications

The transmission of stored video across an ATM network is considered for interactive applications with bounded reaction times. The performance of the services renegotiated VBR (RVBR) and renegotiated CBR (RCBR) is investigated for this class of applications by trace-driven simulations. The goal is to determine the most efficient service for interactive applications. Here we present three basic results. First, for delay sensitive applications smoothing the video stream in advance is much more efficient than adding smoothing buffers to the network switches. Second, services with renegotiation (RCBR, RVBR) are better suited for interactive applications than the static services CBR and VBR. Third, the RVBR service with a deterministic call admission control scheme is the best choice for interactive applications that require small reaction times.     

突发业务下的移动自组织网DSR协议仿真性能分析

移动自组织网络是一组由移动节点组成的无线网络。它的性能已经被广泛的进行了研究,但是这些研究主要是针对节点的移动性和网络的规模来展开的。近年来,移动自组织网在传输视频、音频、数据、图像等多媒体上的应用越来越多,因此自组织网在传输不同业务模型时的性能分析也引起了人们的广泛关注。本文中,我们主要研究分析了移动自组织网DSR协议在传输VBR业务时的性能,并且将仿真结果和传输CBR业务时的结果进行了比较。通过进一步的分析,我们得出与传输VBR业务相比,在传输CBR业务时,移动自组织网DSR协议性能明显提高。