228 research outputs found
Enabling error-resilient internet broadcasting using motion compensated spatial partitioning and packet FEC for the dirac video codec
Video transmission over the wireless or wired
network require protection from channel errors since compressed video bitstreams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, a simple, low complexity and patent free error-resilient coding is proposed. It is based upon the idea of using spatial partitioning on the motion compensated residual frame without employing the transform coefficient coding. The proposed scheme is intended for open source Dirac video codec in order to enable the codec to be used for Internet
broadcasting. By partitioning the wavelet transform coefficients of the motion compensated residual frame into groups and independently processing each group using arithmetic coding and Forward Error Correction (FEC), robustness to transmission errors over the packet erasure
wired network could be achieved. Using the Rate
Compatibles Punctured Code (RCPC) and Turbo Code
(TC) as the FEC, the proposed technique provides
gracefully decreasing perceptual quality over packet loss rates up to 30%. The PSNR performance is much better when compared with the conventional data partitioning only methods. Simulation results show that the use of multiple
partitioning of wavelet coefficient in Dirac can achieve up to 8 dB PSNR gain over its existing un-partitioned method
Error-resilient performance of Dirac video codec over packet-erasure channel
Video transmission over the wireless or wired network requires error-resilient mechanism since compressed video bitstreams are sensitive to transmission errors because of the use of predictive coding and variable length coding. This paper investigates the performance of a simple and low complexity error-resilient coding scheme which combines source and channel coding to protect compressed bitstream of wavelet-based Dirac video codec in the packet-erasure channel. By partitioning the wavelet transform coefficients of the motion-compensated residual frame into groups and independently processing each group using arithmetic and Forward Error Correction (FEC) coding, Dirac could achieves the robustness to transmission errors by giving the video quality which is gracefully decreasing over a range of packet loss rates up to 30% when compared with conventional FEC only methods. Simulation results also show that the proposed scheme using multiple partitions can achieve up to 10 dB PSNR gain over its existing un-partitioned format. This paper also investigates the error-resilient performance of the proposed scheme in comparison with H.264 over packet-erasure channel
Research and developments of distributed video coding
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The recent developed Distributed Video Coding (DVC) is typically suitable for the applications such as wireless/wired video sensor network, mobile camera etc. where the traditional video coding standard is not feasible due to the constrained computation at the encoder. With DVC, the computational burden is moved from encoder to decoder. The compression efficiency is achieved via joint decoding at the decoder. The practical application of DVC is referred to Wyner-Ziv video coding (WZ) where the side information is available at the decoder to perform joint decoding. This join decoding inevitably causes a very complex decoder. In current WZ video coding issues, many of them emphasise how to improve the system coding performance but neglect the huge complexity caused at the decoder. The complexity of the decoder has direct influence to the system output. The beginning period of this research targets to optimise the decoder in pixel domain WZ video coding (PDWZ), while still achieves similar compression performance. More specifically, four issues are raised to optimise the input block size, the side information generation, the side information refinement process and the feedback channel respectively.
The transform domain WZ video coding (TDWZ) has distinct superior performance to the normal PDWZ due to the exploitation in spatial direction during the encoding. However, since there is no motion estimation at the encoder in WZ video coding, the temporal correlation is not exploited at all at the encoder in all current WZ video coding issues. In the middle period of this research, the 3D DCT is adopted in the TDWZ to remove redundancy in both spatial and temporal direction thus to provide even higher coding performance. In the next step of this research, the performance of transform domain Distributed Multiview Video Coding (DMVC) is also investigated. Particularly, three types transform domain DMVC frameworks which are transform domain DMVC using TDWZ based 2D DCT, transform domain DMVC using TDWZ based on 3D DCT and transform domain residual DMVC using TDWZ based on 3D DCT are investigated respectively.
One of the important applications of WZ coding principle is error-resilience. There have been several attempts to apply WZ error-resilient coding for current video coding standard e.g. H.264/AVC or MEPG 2. The final stage of this research is the design of WZ error-resilient
scheme for wavelet based video codec. To balance the trade-off between error resilience ability and bandwidth consumption, the proposed scheme emphasises the protection of the Region of Interest (ROI) area. The efficiency of bandwidth utilisation is achieved by mutual efforts of WZ coding and sacrificing the quality of unimportant area. In summary, this research work contributed to achieves several advances in WZ video coding. First of all, it is targeting to build an efficient PDWZ with optimised decoder. Secondly, it aims to build an advanced TDWZ based on 3D DCT, which then is applied into multiview video coding to realise advanced transform domain DMVC. Finally, it aims to design an efficient error-resilient scheme for wavelet video codec, with which the trade-off between bandwidth consumption and error-resilience can be better balanced
Resilient Digital Video Transmission over Wireless Channels using Pixel-Level Artefact Detection Mechanisms
Recent advances in communications and video coding technology have brought multimedia communications into everyday life, where a variety of services and applications are being integrated within different devices such that multimedia content is provided everywhere and on any device. H.264/AVC provides a major advance on preceding video coding standards obtaining as much as twice the coding efficiency over these standards (Richardson I.E.G., 2003, Wiegand T. & Sullivan G.J., 2007). Furthermore, this new codec inserts video related information within network abstraction layer units (NALUs), which facilitates the transmission of H.264/AVC coded sequences over a variety of network environments (Stockhammer, T. & Hannuksela M.M., 2005) making it applicable for a broad range of applications such as TV broadcasting, mobile TV, video-on-demand, digital media storage, high definition TV, multimedia streaming and conversational applications. Real-time wireless conversational and broadcast applications are particularly challenging as, in general, reliable delivery cannot be guaranteed (Stockhammer, T. & Hannuksela M.M., 2005). The H.264/AVC standard specifies several error resilient strategies to minimise the effect of transmission errors on the perceptual quality of the reconstructed video sequences. However, these methods assume a packet-loss scenario where the receiver discards and conceals all the video information contained within a corrupted NALU packet. This implies that the error resilient methods adopted by the standard operate at a lower bound since not all the information contained within a corrupted NALU packet is un-utilizable (Stockhammer, T. et al., 2003).peer-reviewe
A testbed of erasure coding on video streaming system over lossy networks
As one of the most challenging aspects of streaming video over lossy networks, the technology for controlling packet losses has attracted more and more attention. Erasure coding is one of the ideal choices to deal with this problem. In most cases, the researchers need an effective method or tool to validate the erasure codes used for dealing with different packet loss patterns. Although some previous work has been done on employing erasure codes in video streaming system, few actual buildups and experiments which involve implementation of erasure codes against real packet loss in streaming systems have been reported. In this paper, we focus on constructing a testbed that integrates loss pattern generation and erasure coding implementation into video streaming services over lossy networks. With this approach, we are able to assess the capability of erasure coding in packet loss control and compare the performances of the video streaming systems with and without erasure coding. As an example, we have implemented the Reed-Solomon (7, 5) code for protecting MPEG streaming data under random packet losses. Experiment results show that the replay quality can be improved significantly by using erasure coding in video streaming systems, and that the testbed can suggest appropriate erasure code parameters for different loss environments
Enabling error-resilient internet broadcasting using motion compensated spatial partitioning and packet FEC for the Dirac Video Codec
Video transmission over the wireless or wired network require protection from channel errors since compressed video bitstreams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, a simple, low complexity and patent free error-resilient coding is proposed. It is based upon the idea of using spatial partitioning on the motion compensated residual frame without employing the transform coefficient coding. The proposed scheme is intended for open source Dirac video codec in order to enable the codec to be used for Internet broadcasting. By partitioning the wavelet transform coefficients of the motion compensated residual frame into groups and independently processing each group using arithmetic coding and Forward Error Correction (FEC), robustness to transmission errors over the packet erasure wired network could be achieved. Using the Rate Compatibles Punctured Code (RCPC) and Turbo Code (TC) as the FEC, the proposed technique provides gracefully decreasing perceptual quality over packet loss rates up to 30%. The PSNR performance is much better when compared with the conventional data partitioning only methods. Simulation results show that the use of multiple partitioning of wavelet coefficient in Dirac can achieve up to 8 dB PSNR gain over its existing un-partitioned method
Network coding meets multimedia: a review
While every network node only relays messages in a traditional communication system, the recent network coding (NC) paradigm proposes to implement simple in-network processing with packet combinations in the nodes. NC extends the concept of "encoding" a message beyond source coding (for compression) and channel coding (for protection against errors and losses). It has been shown to increase network throughput compared to traditional networks implementation, to reduce delay and to provide robustness to transmission errors and network dynamics. These features are so appealing for multimedia applications that they have spurred a large research effort towards the development of multimedia-specific NC techniques. This paper reviews the recent work in NC for multimedia applications and focuses on the techniques that fill the gap between NC theory and practical applications. It outlines the benefits of NC and presents the open challenges in this area. The paper initially focuses on multimedia-specific aspects of network coding, in particular delay, in-network error control, and mediaspecific error control. These aspects permit to handle varying network conditions as well as client heterogeneity, which are critical to the design and deployment of multimedia systems. After introducing these general concepts, the paper reviews in detail two applications that lend themselves naturally to NC via the cooperation and broadcast models, namely peer-to-peer multimedia streaming and wireless networkin
Error resilient stereoscopic video streaming using model-based fountain codes
Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 2009.Thesis (Ph.D.) -- Bilkent University, 2009.Includes bibliographical references leaves 101-110.Error resilient digital video streaming has been a challenging problem since
the introduction and deployment of early packet switched networks. One of
the most recent advances in video coding is observed on multi-view video coding
which suggests methods for the compression of correlated multiple image
sequences. The existing multi-view compression techniques increase the loss sensitivity
and necessitate the use of efficient loss recovery schemes. Forward Error
Correction (FEC) is an efficient, powerful and practical tool for the recovery of
lost data. A novel class of FEC codes is Fountain codes which are suitable to be
used with recent video codecs, such as H.264/AVC, and LT and Raptor codes are
practical examples of this class. Although there are many studies on monoscopic
video, transmission of multi-view video through lossy channels with FEC have
not been explored yet. Aiming at this deficiency, an H.264-based multi-view
video codec and a model-based Fountain code are combined to generate an effi-
cient error resilient stereoscopic streaming system. Three layers of stereoscopic
video with unequal importance are defined in order to exploit the benefits of Unequal
Error Protection (UEP) with FEC. Simply, these layers correspond to intra frames of left view, predicted frames of left view and predicted frames of right
view. The Rate-Distortion (RD) characteristics of these dependent layers are de-
fined by extending the RD characteristics of monoscopic video. The parameters
of the models are obtained with curve fitting using the RD samples of the video,
and satisfactory results are achieved where the average difference between the
analytical models and RD samples is between 1.00% and 9.19%. An heuristic
analytical model of the performance of Raptor codes is used to obtain the residual
number of lost packets for given channel bit rate, loss rate, and protection
rate. This residual number is multiplied with the estimated average distortion
of the loss of a single Network Abstraction Layer (NAL) unit to obtain the total
transmission distortion. All these models are combined to minimize the end-toend
distortion and obtain optimal encoder bit rates and UEP rates. When the
proposed system is used, the simulation results demonstrate up to 2dB increase
in quality compared to equal error protection and only left view error protection.
Furthermore, Fountain codes are analyzed in the finite length region, and
iterative performance models are derived without any assumptions or asymptotical
approximations. The performance model of the belief-propagation (BP)
decoder approximates either the behavior of a single simulation results or their
average depending on the parameters of the LT code. The performance model of
the maximum likelihood decoder approximates the average of simulation results
more accurately compared to the model of the BP decoder. Raptor codes are
modeled heuristically based on the exponential decay observed on the simulation
results, and the model parameters are obtained by line of best fit. The analytical
models of systematic and non-systematic Raptor codes accurately approximate
the experimental average performance.Tan, A SerdarPh.D
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