Wyner-Ziv Codec Research Articles

Robust distributed video coding for wireless multimedia sensor networks

Coding complexity and error-resilience are the two key factors for video streaming in Wireless Multimedia Sensor Networks (WMSNs). Towards this objective, this paper proposes a Robust Distributed Video Coding (RDVC) framework to optimize the quality of video transmission for WMSNs. A new error-resilient Key frame coding scheme is proposed based on the protection of Wyner-Ziv Coding (WZC), in which additional Wyner-Ziv bits play a significant role for better error resilience and better Rate/Distortion (RD) performance. In addition, following the theoretical background of Distributed Joint Source Channel Coding (DJSCC), a novel distributed source channel codec based on Group Puncture Rate Adaptive IRA code (GPRA-IRA) is proposed, upon which the error-resilient Wyner-Ziv codec is designed. These experimental results show that the proposed RDVC scheme outperforms the relevant coding in terms of RD performance, notably by up to 1-3 dB, while achieving a lower encoding complexity.

Band-Level Correlation Noise Modeling for Wyner–Ziv Video Coding with Gaussian Mixture Models

As one of the most adopted distributed video coding approaches in the literature, Wyner---Ziv (WZ) video coding is not yet on par with the motion-compensated predictive coding solutions with respect to rate---distortion (RD) performance. One of the essential reasons lies in the absence of reliable knowledge of the correlation statistics between source and side information. Most of the existing works assume a probability distribution of the statistical dependency to be Laplacian, which is not accurate but computationally cheap. In this paper, a correlation estimation based on Gaussian mixture model is proposed for the band-level correlation noise of discrete cosine transform domain Wyner---Ziv codec. The statistics of the correlation noise between WZ frame and corresponding side information is analyzed by considering the temporal correlation and quantization distortion. Accordingly, the model parameters for correlation noise are estimated offline and utilized online in consequent decoding. The simulation results of Kullback---Leibler divergence show that the proposed model has higher accuracy than the Laplacian one. Experimental results demonstrate that the WZ codec incorporated with the proposed model can achieve very competitive RD performance, especially for the sequence with high motion contents and large group of picture (GOP) size.

Progressively refined wyner-ziv video coding for visual sensors

Wyner-Ziv video coding constitutes an alluring paradigm for visual sensor networks, offering efficient video compression with low complexity encoding characteristics. This work presents a novel hash-driven Wyner-Ziv video coding architecture for visual sensors, implementing the principles of successively refined Wyner-Ziv coding. To this end, so-called side-information refinement levels are constructed for a number of grouped frequency bands of the discrete cosine transform. The proposed codec creates side-information by means of an original overlapped block motion estimation and pixel-based multihypothesis prediction technique, specifically built around the pursued refinement strategy. The quality of the side-information generated at every refinement level is successively improved, leading to gradually enhanced Wyner-Ziv coding performance. Additionally, this work explores several temporal prediction structures, including a new hierarchical unidirectional prediction structure, providing both temporal scalability and low delay coding. Experimental results include a thorough evaluation of our novel Wyner-Ziv codec, assessing the impact of the proposed successive refinement scheme and the supported temporal prediction structures for a wide range of hash configurations and group of pictures sizes. The results report significant compression gains with respect to benchmark systems in Wyner-Ziv video coding (e.g., up to 42.03% over DISCOVER) as well as versus alternative state-of-the-art schemes refining the side-information.

Distributed video coding with video analytics information for video surveillance application

A lightweight distributed video coding scheme is presented for video surveillance applications. Background frames and foreground maps are generated using a video analytics module on the decoder side. Only sub-frames containing foreground blocks are encoded using a transform-domain Wyner-Ziv codec. A decoded frame is synthesised with the reconstructed sub-frames and the background frame. Through a simulation, the proposed scheme is shown to achieve better than state-of-the-art coding efficiency while reducing coding complexity greatly both at the encoder and the decoder.

Side Information Extrapolation Using Motion-aligned Auto Regressive Model for Compressed Sensing based Wyner-Ziv Codec

In this paper, we propose a compressed sensing (CS) based Wyner-Ziv (WZ) codec using motion-aligned auto regressive model (MAAR) based side information (SI) extrapolation to improve the compression performance of low-delay distributed video coding (DVC). In the CS based WZ codec, the WZ frame is divided into small blocks and CS measurements of each block are acquired at the encoder, and a specific CS reconstruction algorithm is proposed to correct errors in the SI using CS measurements at the decoder. In order to generate high quality SI, a MAAR model is introduced to improve the inaccurate motion field in auto regressive (AR) model, and the Tikhonov regularization on MAAR coefficients and overlapped block based interpolation are performed to reduce block effects and errors from over-fitting. Simulation experiments show that our proposed CS based WZ codec associated with MAAR based SI generation achieves better results compared to other SI extrapolation methods.

Error Protection of Wavelet Scalable Video Streaming Using Wyner-Ziv Technique over a Lossy Network

Abstract This paper presents a novel error resilience scheme for wavelet scalable video coding. We use Wyner-Ziv codec to produce extra bits protecting the important parts of the embedded video streaming. At the same time these bits also as the second description of important parts are transmitted over auxiliary channel to the receiver for error resilience. The errors in the embedded video streaming can be corrected by Wyner-Ziv description which regards the decoded frame as side information. Moreover, Wyner-Ziv decoder utilizes a coarse estimated version of the corrupted parts exploiting frame correlation in wavelet video decoder to generate a refine version. Simulation results show that our proposed method can achieve much better performance compared with Forward Error Correction code. Meanwhile, this error resilient algorithm can achieve 2-3 dB PSNR gains over the motion compensation error concealment.

An Error Resilient Video Coding Scheme Using Embedded Wyner–Ziv Description With Decoder Side Non-Stationary Distortion Modeling

In this paper, we propose a generic error resilient video coding (ERVC) scheme using embedded Wyner-Ziv (WZ) description. At the encoder side, a joint source-channel R-D optimized mode selection (JSC-RDO-MS) algorithm with WZ-coded anchor frames is statistically studied and developed. Given a stationary first-order Markov Gaussian source, the proposed mode optimization is justified by an analysis of the RD impact on the WZ bit-rate. JSC-RDO-MS involves in the estimation of expected rate and distortion of WZ coding with the unavailable side information, and the WZ bit-rate of each coding mode is determined based on the error correction capability of the specific WZ codec. At the decoder side, an online correlation noise model between the source and the side-information is proposed with a mixture of Laplacians whose parameters are attained to reflect the coherence of the motion field of successive frames and the energy of prediction residual. Each mixture component represents the statistical distribution of prediction residuals, and the mixing coefficients represent the amount of errors in motion compensation. The proposed scheme achieves the so-called classification gain by exploiting the spatially non-stationary characteristics of the motion field and texture. Extensive experimental results show that the proposed WZ-ERVC scheme achieves a better overall RD performance than existing ERVC schemes, and the proposed modeling algorithm also significantly outperforms the conventional Laplacian model by up to 2 dB.

Distributed Estimation and Coding: A Sequential Framework Based on a Side-Informed Decomposition

We propose a sequential framework for the distributed multiple-sensor estimation and coding problem that decomposes the problem into a series of side-informed source coding problems and enables construction of good codecs. Our construction relies on a separation result for the simplified scenario where information from one sensor is to be sent to the CP that already has information regarding the desired signal. We show that the optimal encoder decoder combination, in this setting, can be decomposed, without loss in performance, into two steps: A first preprocessing step to extract relevant information from the indirect observation with consideration of the side information, followed by a second step of side-informed encoding of the preprocessed output. A recursive exploit of the decomposition coupled with side-informed transform coding allows us to construct encoders by reusing scalar Wyner-Ziv codecs. We develop a numerical procedure for obtaining bounds delineating the best achievable performance for the proposed sequential framework and construct and demonstrate a practical codec in the proposed framework that achieves empirical performance close to the bound. Furthermore, we also compare the bounds for the sequential scheme against bounds for a number of alternate schemes-for some of which codec constructions are obvious and others for which codec constructions are inobvious. Our results show that, in most cases, our codec exceeds the performance bound of schemes offering obvious constructions. The achievable bound for our sequential framework is also shown to be close to a general nonconstructive distributed bound that does not impose the sequential constraint indicating that the sequential approach may not cause a significant performance compromise.

화소 영역 Wyner-Ziv코덱에서 적응적 예측을 통한 보조정보 생성 방식과 성능 비교

DVC (Distributed Video Coding) allows us to explore the video statistics at the decoder side, resulting in a less complex encoder and more complex decoder. In this approach, it is important to generate a good prediction to the current Wyner-Ziv frame, called side information, which plays a crucial role in the overall performance of a DVC system. Conventional MCFI (motion compensated frame interpolation) techniques, which explore temporal correlations between neighbor frames of the current frame, preform the block-based or object-based motion estimation, but, they do not include the basis frame for the Wyner-Ziv frame. This paper proposes an efficient way to get better side information, by finding the average frame between neighbor frames and by comparing adaptively the candidate blocks. Through computer simulations, it is shown that the proposed method can improve the performance up to 0.4dB and provide better subjective and objective visual qualities in Wyner-Ziv CODEC.

A Wyner-Ziv Video Transcoder

Wyner-Ziv (WZ) coding of video utilizes simple encoders and highly complex decoders. A transcoder from a WZ codec to a traditional codec can potentially increase the range of applications for WZ codecs. We present a transcoder scheme from the most popular WZ codec architecture to a differential pulse code modulation/discrete cosine transform codec. As a proof of concept, we implemented this transcoder using a simple pixel-domain WZ codec and the standard H.263+. The transcoder design aims at reducing complexity as a large amount of computation is saved by reusing the motion estimation, calculated at the side information generation process, and the l-frame streams. New approaches are used to generate side information and to map motion vectors for the transcoder. Results are presented to demonstrate the transcoder performance.

Side-Information Generation for Temporally and Spatially Scalable Wyner-Ziv Codecs

The distributed video coding paradigm enables video codecs to operate with reversed complexity, in which the complexity is shifted from the encoder toward the decoder. Its performance is heavily dependent on the quality of the side information generated by motio estimation at the decoder. We compare the rate-distortion performance of different side-information estimators, for both temporally and spatially scalable Wyner-Ziv codecs. For the temporally scalable codec we compared an established method with a new algorithm that uses a linear-motion model to produce side-information. As a continuation of previous works, in this paper, we propose to use a super-resolution method to upsample the nonkey frame, for the spatial scalable codec, using the key frames as reference. We verify the performance of the spatial scalable WZ coding using the state-of-the-art video coding standard H.264/AVC.

Wyner–Ziv Switching Scheme for Multiple Bit-Rate Video Streaming

This paper proposes a Wyner-Ziv (WZ) switching scheme for multiple bit-rate (MBR) video streaming over networks. Identical video content is encoded into a set of normal streams, which are generated by conventional hybrid video coding with multiple bit rates, so that streaming can dynamically switch among these normal streams according to available bandwidth. At encoder side, the WZ codec generates a switching stream by compressing the reconstructed frames of a certain normal stream that will be switched to, no matter which normal stream it switches from. At decoder side, for switching to the same frame, the same WZ switching stream is used to reconstruct the switching-to frame by taking the switching-from frame as the side information. The number of required WZ bits depends on the inherent mutual correlation between two frames switching to and from. Since the WZ switching streams are generated independently of the normal switching-from streams, given normal streams that can switch from any one to another, the proposed scheme reduces the number of switching streams from to . Furthermore, switching streams do not deteriorate the coding efficiency of normal streams when no switching occurs. However a big problem here, similar to requesting bits in distributed video coding, is how many WZ bits should be transmitted when a switching happens because the streaming scenario does not tolerate too much extra delay caused by the requests back and forth. Therefore, a Laplacian model, which is proved in the simplified case, is proposed to characterize the correlation between switching-to and switching-from frames. It can be used to accurately estimate the number of WZ bits at the server side.

An efficient hybrid distributed video coding

An efficient hybrid distributed video coding (HDVC) scheme combining residual coding, SW-SPIHT coding and intra-mode decision technology is proposed to offer good rate-distortion performance and low-complexity encoding. The scheme adopts the wavelet-domain Wyner-Ziv codec to compress the residual frame between the current frame and its reference frame. An intra-mode decision based on the temporal and spatial correlation is made to determine whether a wavelet block is better coded or not. When the estimated correlation is weak, we use intra-SPIHT coding; otherwise SW-SPIHT(Slepian-Wolf SPIHT) coding is adopted. Experimental results indicate the proposed HDVC achieves evident improvement than the referenced.