Improving Turbo Codec Integration In Pixel-Domain Distributed Video Coding

The field of distributed video coding (DVC) theory has received a lot of attention in recent years and effective encoding techniques have been proposed. In the present work the framework of pixel domain Wyner-Ziv coding of video frames is considered, following the scheme proposed in A. Aaron et al. (2002). Some key frames are supposed to be available at the decoder while other frames are Wyner-Ziv encoded using turbo codes; at the decoder motion compensated interpolation between the key frames is performed in order to construct the side information for the Wyner-Ziv frame decoding. In this paper an improved model for the correlation noise between the side information frame and the original one is proposed. It is shown that modeling the nonstationary nature of the noise leads to substantial gain in the rate-distortion performance. Furthermore, by considering the memory of the noise, we show that some further gain can be obtained by placing an interleaver before the turbo codec so as to spread the correlation noise all over the fram

Improved Wyner-Ziv video coding efficiency using bit plane prediction

The research work is partially funded by STEPS-Malta and partially by the European Union - ESF 1.25.Distributed Video Coding (DVC) is a coding paradigm where video statistics are exploited, partially or totally, at the decoder. The performance of such a codec depends on the accuracy of the soft-input information estimated at the decoder, which is affected by the quality of the side information (SI) and the dependency model. This paper studies the discrepancies between the bit planes of the Wyner-Ziv (WZ) frames and the corresponding bit planes of the SI. The relationship between these discrepancies is then exploited to predict the locations where the bit plane of the SI is expected to differ from that of the original WZ frame. This information is then used to derive more accurate soft-input values that achieve better compression efficiencies. Simulation results demonstrate that a WZ bit-rate reduction of 9.4% is achieved for a given video quality.peer-reviewe

Improving decoding speed for parallel distributed video coding architectures

The research work disclosed in this publication is partially funded by the Strategic Educational Pathways Scholarship Scheme (Malta). The scholarship is part-financed by the European Union – European Social Fund. (ESF 1.25).The Distributed Video Coding (DVC) paradigm is suitable for devices which have limited encoding capabilities. However, it is characterized by excessive decoding delays which compromise their application for time constrained services. This limitation can be mitigated by adopting parallel DVC architectures. Yet, the traditional Gray-code or binary-code representations have a non-uniform distribution of mismatch across bit-planes, resulting in uneven decoding times which hinder parallel decoding. This work proposes an alternative indexing scheme, where mismatch is distributed more uniformly amongst bit-planes and thus comparable decoding delays are expected, facilitating parallel implementations. This method reduces decoding time by up to 32% compared to architectures using simple parallel techniques, with a slight loss of 0.06dB in RD performance.peer-reviewe

THE VISNET II DVC CODEC: ARCHITECTURE, TOOLS AND PERFORMANCE

ABSTRACT This paper introduces the VISNET II DVC codec. This codec achieves very high RD performance thanks to the efficient combination of many state-of-the-art coding tools into INTRODUCTION With the wide deployment of mobile and wireless networks, a growing number of emerging applications, such as lowpower sensor networks, video surveillance cameras and mobile communications, rely on an up-link model rather than the typical down-link communication model. Typically, these applications are characterized by many senders transmitting data to a central receiver. In this context, light encoding or a flexible distribution of the codec complexity, robustness to packet losses, high compression efficiency and low latency/delay are important requirements. To address the needs of these up-link applications, the usual predictive video coding paradigm has been revisited based on Information Theory theorems from the 70s. The Slepian-Wolf (SW) theorem [1] establishes lower bounds on the achievable rates for the lossless coding of two or more correlated sources. More specifically, considering two statistically dependent random signals X and Y, it is well-known that the lower bound for the rate is given by the joint entropy H(X,Y) when these two signals are jointly encoded (as in conventional predictive coding). Conversely, when these two signals are independently encoded but jointly decoded (distributed coding), the SW theorem states that the minimum rate is still H(X,Y) with a residual error probability which tends towards 0 for long sequences. Later, Wyner and Ziv (WZ) have extended the SW theorem and showed that the result holds for the lossy coding case under the assumptions that the sources are jointly Gaussian and a mean square error distortion measure is used [2]. Subsequently, it was shown that this result remains valid as long as the difference between X and Y is Gaussian. Video coding schemes based on these theorems are referred to as Distributed Video Coding (DVC) solutions. Since the new coding paradigm is based on a statistical framework and does not rely on joint encoding, DVC architectures may provide several functional benefits which are rather important for many emerging applications: i) flexible allocation of the global video codec complexity; ii) improved error resilience; iii) codec independent scalability; and iv) exploitation of multiview correlation. Based on these theoretical results, practical implementations of DVC have been proposed since 2002. The PRISM (Power-efficient, Robust, hIgh compression Syndrome-based Multimedia coding) [3] solution works at the block level and performs motion estimation at the decoder. Based on the amount of temporal correlation, estimated using a zeromotion block difference, each block can either be conventionally (intra) coded, skipped or coded using distributed coding principles. Another DVC architecture working at frame level has been proposed in In this paper, the DVC codec developed within the European Network of Excellence VISNET II project [5] is described. This codec is based on the early architecture in VISNET II CODEC ARCHITECTURE AND TOOLS This section provides a description of the VISNET II DVC codec architecture and tools illustrated i

Advanced distributed video coding techniques

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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