Wyner-Ziv Frame Research Articles

Multi-View Distributed Video Coding Based on Discrete Cosine

To investigate the allocation scheme of the multi-view distributed video coding (DVC), the corresponding improvements are proposed correspondingly for traditional multi-view DVC. Traditional multi-view DVC (Wyner-Ziv DVC) encodes for all areas of Wyner-Ziv frame indiscriminately based on Turbo or LDPC. In this kind of encoding process, with regard to violent motor area, decoder can't decode violent motor area accurately and also send more solicited message to feedback channel, which lowers the code efficiency and decodes inaccurately for violent motor area, it causes a part of area distortion in the image. In this paper, a distributed video encryption algorithm is proposed which based on discrete cosine transform (DCT). The algorithm combines decision criteria of ROI to get violent motor area and non-violent motor area. For violent motor area, to extract low frequency coefficient of DCT as DCT-R algorithm to assist decoder end to decode, decoder utilizes low frequency coefficient of DCT which has already been decoded to carry on bi-directional movement evaluation. Simulation experiment tests and verifies the improved algorithm effectiveness of proposed multi-view DVC in this paper.

Re-estimation of Motion and Reconstruction for Distributed Video Coding

Transform domain Wyner-Ziv (TDWZ) video coding is an efficient approach to distributed video coding (DVC), which provides low complexity encoding by exploiting the source statistics at the decoder side. The DVC coding efficiency depends mainly on side information and noise modeling. This paper proposes a motion re-estimation technique based on optical flow to improve side information and noise residual frames by taking partially decoded information into account. To improve noise modeling, a noise residual motion re-estimation technique is proposed. Residual motion compensation with motion updating is used to estimate a current residue based on previously decoded frames and correlation between estimated side information frames. In addition, a generalized reconstruction algorithm to optimize a multihypothesis reconstruction is proposed. The proposed techniques using motion and reconstruction re-estimation (MORE) are integrated in the SING TDWZ codec, which uses side information and noise learning. For Wyner-Ziv frames using GOP size 2, the MORE codec significantly improves the TDWZ coding efficiency with an average (Bjøntegaard) PSNR improvement of 2.5 dB and up to 6 dB improvement compared with DISCOVER.

Side Information Generation for Distributed Video Coding Using Spatiotemporal Joint Bilinear Upsampling

Distributed video coding presents a viable solution for power-constrained multimedia communication. However, its relatively low coding efficiency compared to the conventional video coding schemes remains a challenging issue. The rate-distortion performance of distributed video coding is highly dependent on the quality of side information generated at the decoder and various techniques have been proposed to improve the side information quality in block-based and frame-based distributed video coding architectures. In this paper, a robust spatiotemporal joint bilateral upsampling based side information generation method is proposed. The proposed side information generation method is based on a block-based low-complexity distributed video coding architecture with adaptive block coding mode classification. A partially reconstructed Wyner-Ziv (WZ) frame with skip and key blocks is downsampled and spatiotemporal error concealment and joint bilateral upsampling are used to generate the side information. Simulation results show that the proposed method improves the quality of side information significantly while keeping low computational complexity.

Multiple descriptions Wyner–Ziv video coding

This paper proposes a multiple descriptions Wyner–Ziv video coding (MDWZVC) architecture, which combines the merits of multiple descriptions coding (MDC) and Wyner–Ziv video coding (WZVC). All of the Wyner–Ziv frames (WZFs) are sub-sampled into four low resolution parallel phases to generate four descriptions, which are encoded and transmitted to the decoder independently. In addition, a successive refined side information (SI) algorithm, which is suitable for the video coding architecture is proposed to exploit both temporal and spatial correlations of the video frames. The simulation results show the SI quality, the peak signal to noise ratio (PSNR) and the rate-distortion (R-D) performance improved with the increasing numbers of received descriptions. By updating the SI quality and reconstruction results of the already decoded descriptions, the R-D performance improved further more. When all of the four descriptions correctly received, the R-D performance improvement of the proposed MDWZVC architecture over DISCOVER codec can be up to 1.8dB, which indicates the effectiveness of the proposed architecture.

Spatial correlation-based side information refinement for distributed video coding

Distributed video coding (DVC) architecture designs, based on distributed source coding principles, have benefitted from significant progresses lately, notably in terms of achievable rate-distortion performances. However, a significant performance gap still remains when compared to prediction-based video coding schemes such as H.264/AVC. This is mainly due to the non-ideal exploitation of the video sequence temporal correlation properties during the generation of side information (SI). In fact, the decoder side motion estimation provides only an approximation of the true motion. In this paper, a progressive DVC architecture is proposed, which exploits the spatial correlation of the video frames to improve the motion-compensated temporal interpolation (MCTI). Specifically, Wyner-Ziv (WZ) frames are divided into several spatially correlated groups that are then sent progressively to the receiver. SI refinement (SIR) is performed as long as these groups are being decoded, thus providing more accurate SI for the next groups. It is shown that the proposed progressive SIR method leads to significant improvements over the Discover DVC codec as well as other SIR schemes recently introduced in the literature.

Distributed Video Coding Based on Multiple-source Correlation Model

Distributed Video Coding (DVC) is a new video coding paradigm which has the ability to shift coding complexity from encoder to decoder. State-of-art DVC schemes are mainly based on two-source correlation model and only one correlation channel between side information and wyner-ziv frame is considered. In this paper, multiple-source correlation model is introduced into a famous DVC scheme, namely Transform Domain Wyner-Ziv video coder (TDWZ). A soft-input computing algorithm based on multiple-source correlation model is firstly proposed. The correlations a mong multiple side information are separately exploited. Then a new reconstruction function based on multiple source correlation model is also proposed to improve reconstructed image's quality. Experimental results show that the proposed algorithms can effectively improve the coding performance of systems.

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.

Fusion of Global and Local Motion Estimation for Distributed Video Coding

The quality of side information plays a key role in distributed video coding. In this paper, we propose a new approach that consists of combining global and local motion compensation at the decoder side. The parameters of the global motion are estimated at the encoder using scale invariant feature transform features. Those estimated parameters are sent to the decoder in order to generate a globally motion compensated side information. Conversely, a locally motion compensated side information is generated at the decoder based on motion-compensated temporal interpolation of neighboring reference frames. Moreover, an improved fusion of global and local side information during the decoding process is achieved using the partially decoded Wyner-Ziv frame and decoded reference frames. The proposed technique improves significantly the quality of the side information, especially for sequences containing high global motion. Experimental results show that, as far as the rate-distortion performance is concerned, the proposed approach can achieve a PSNR improvement of up to 1.9 dB for a Group of Pictures (GOP) size of 2, and up to 4.65 dB for larger GOP sizes, with respect to the reference DISCOVER codec.

Efficient Distributed Video Coding System without Feedback Channel

In distributed video coding (DVC) systems, the complexity of encoders is greatly reduced by removing the motion estimation operations in encoders, since the correlation between frames is utilized in decoders. The transmission of parity bits is requested through the feedback channel, until the related errors are corrected to decode the Wyner-Ziv frames. The requirement to use the feedback channel limits the application of DVC systems. In this paper, we propose an efficient method to remove the feedback channel in DVC systems. First, a simple side information generation method is proposed to calculate the amount of parity bits in the encoder, and it is shown that the proposed method yields good performance with low complexity. Then, by calibrating the theoretical entropy with three parameters, we can calculate the amount of parity bits in the encoder and remove the feedback channel. Moreover, an adaptive method to determine quantization parameters for key frames is proposed. Extensive computer simulations show that the proposed method yields better performance than conventional methods.

분산 동영상 부호화 시스템을 위한 전송률 및 왜곡 제어 방법

간단한 부호기를 사용하는 분산 동영상 부호화 시스템은 복호기에서 생성한 부가정보와 원 Wyner-Ziv (WZ) 프레임간의 차이를 채널부호를 이용해 정정하게 되는데 오류정정이 제대로 이루어지지 않으면 복호기에서 피드백 채널을 통해 추가 패리티 비트를 요청하게 된다. 특히 이동통신 등과 같이 제한된 환경에서 분산 동영상 부호화 시스템을 사용하기 위해서는 전송률 및 부호화 왜곡을 효율적으로 제어할 수 있어야 한다. 본 논문에서는 부호기에서 비트 전송률을 제한함으로써 통신환경에 맞도록 비트 전송률을 일정하게 제어하는 방법을 제안한다. 제안하는 방법은 전송률을 적절히 제어할 뿐 만 아니라 부호화 성능도 일정하게 유지하는 장점이 있다. In the distributed video coding (DVC) system, the difference between the side information and the original Wyner-Ziv frame is corrected using channel codes and the additional parity bits are requested through feedback channel if the error is not corrected. The efficient bit rate control is important to use the DVC system in the band-limited channel, such as mobile communication environments. In this paper, the constant bit rate control method in the encoder of the DVC system is proposed. The coding performance as well as the bit rate is efficiently controlled by the proposed method.

Efficient bit rate control method for distributed video coding system

An efficient bit rate control method for the transform domain distributed video coding (DVC) system is proposed. In order to decide quantization levels of each transform coefficient in the proposed distributed video decoder, a new bitplanewise zigzag scanning method is used. The bit rate can be controlled precisely in the proposed system, since the number of available bit rates is equal to the number of bitplanes. On the other hand, the bit rate is controlled by changing fixed quantization tables in conventional methods. In the proposed DVC system, Wyner-Ziv frames can be efficiently reconstructed by refining the side information with transmitted parity bits. If there is no transmitted parity bit, the side information is not refined and it is considered to be a decoded Wyner-Ziv frame. The side information is refined more precisely, as the amount of transmitted parity bits increases. The proposed DVC system provides superior coding performance with a precise bit rate control compared to conventional methods.

Rate-distortion optimised quantisation for direct current coefficients of Wyner–Ziv frame in unidirectional distributed video coding

This study presents a rate-distortion (RD) optimised quantisation algorithm for direct current (DC) coefficients of the Wyner–Ziv (WZ) frames in unidirectional distributed video coding. As the side information (SI) could be viewed as a ‘corrupted’ version of the original WZ frame, the correlation noise (WZ-SI) can be interpreted as a virtual channel with an error pattern. In this study, the distortion caused by virtual channel errors, besides quantisation errors, is analysed emphatically for unidirectional WZ video coding. In their presented quantisation algorithm, a novel RD model is developed to find out the optimal quantisation step size, in which the quantisation distortion and virtual channel error distortion together with the encoding rate are formulated using the quantisation step size without feedback channels. Then the RD optimal step size for DC coefficients can be solved through minimising the RD cost. In simulations, the comparison of RD performance between their proposed algorithm and the quantisation method used in distributed coding for video services (DISCOVER) is presented. Experimental results show that the proposed RD optimised quantisation for DC coefficients can improve the average peak signal-to-noise ratio of WZ frames by 0.4–1.2 dB for quarter common intermediate format (QCIF) sequences and 0.2–0.4 dB for common intermediate format (CIF), at the expense of increasing the encoding complexity slightly.

Distributed Video Coding With Feedback Channel Constraints

Many of the distributed video coding (DVC) systems described in the literature make use of a feedback channel from the decoder to the encoder to determine the rate. However, the number of requests through the feedback channel is often high, and as a result the overall delay of the system could be unacceptable in practical applications. As a solution, feedback-free DVC systems have been proposed, but the problem with these solutions is that they incorporate a difficult trade-off between encoder complexity and compression performance. Recognizing that a limited form of feedback may be supported in many video-streaming scenarios, in this paper we propose a method for constraining the number of feedback requests to a fixed maximum number of N requests for an entire Wyner-Ziv (WZ) frame. The proposed technique estimates the WZ rate at the decoder using information obtained from previously decoded WZ frames and defines the N requests by minimizing the expected rate overhead. Tests on eight sequences show that the rate penalty is less than 5% when only five requests are allowed per WZ frame (for a group of pictures of size four). Furthermore, due to improvements from previous work, the system is able to perform better than or similar to DISCOVER even when up to two requests per WZ frame are allowed. The practical usefulness of the proposed approach is studied by estimating end-to-end delay and encoder buffer requirements, indicating that DVC with constrained feedback can be an important solution in the context of video-streaming scenarios.

A Wyner-Ziv Video Coding method utilizing mixture correlation noise model

In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the performance of the video coder directly. A mixture correlation noise model in Discrete Cosine Transform (DCT) domain for WZ video coding is established in this paper. Different correlation noise estimation method is used for direct current and alternating current coefficients. Parameter estimation method based on expectation maximization algorithm is used to estimate the Laplace distribution center of direct current frequency band and Mixture Laplace-Uniform Distribution Model (MLUDM) is established for alternating current coefficients. Experimental results suggest that the proposed mixture correlation noise model can describe the heavy tail and sudden change of the noise accurately at high rate and make significant improvement on the coding efficiency compared with the noise model presented by DIStributed COding for Video sERvices (DISCOVER).

Flexible Complexity Control Solution for Transform Domain Wyner-Ziv Video Coding

Most Wyner-Ziv (WZ) video coding solutions in the literature focus on improving the coding efficiency. Recently, a few papers have addressed problems related to the complexity distribution of WZ video coding by sharing the motion estimation process between the encoder and decoder. However, these methods turn out to significantly increase the computational complexity of the encoding process, due to the presence of motion estimation at the encoder, which is less appealing in WZ coding applications, since their primary requirement is a low-encoding complexity. To address this problem, we propose a different approach to complexity control based on the adaptive selection between WZ and intra coding in the WZ frames. This solution is more flexible than the previous ones in that it can be implemented either at the encoder or decoder. The proposed intra mode selection algorithm exploits the spatial and temporal coherency in the transform domain Wyner-Ziv video coding (TDWZ), in order to achieve complexity control between the WZ encoder and decoder. The experimental results illustrate that the proposed algorithm not only effectively distributes the computational complexity over the encoder and decoder, but also retains the low-complexity feature at the encoder. This should make it attractive for a large number of real video applications of the WZ video coding paradigm. Moreover, the coding efficiency of the conventional TDWZ codec without intra mode decision is improved by up to 2 dB by the proposed intra mode selection algorithm.

A Multiple Description Video Codec With Adaptive Residual Distributed Coding

Multiple description coding (MDC) decomposes one single media into several descriptions and transmits them over different channels for error resilience. Each description contributes to improving the reconstructed media quality when decoded. Distributed video coding (DVC) encodes multiple correlated images and utilizes error correction codes to shift the codec complexity to a joint decoder. Combining MDC with DVC (MDVC) yields a stable codec for mobile encoders. In this paper, to improve the MDVC codec performance, image correlations among the MDVC processing modules were exploited to improve reconstructed video quality and enhance transmission robustness. At the side encoder, a DVC-based adaptive differential pulse code modulation was designed to remove interframe redundancy to enhance rate-distortion performances. For the MDVC central decoding, intradescription and interdescription correlations were utilized to dynamically select the best reconstructed frames from two descriptions, instead of selecting just one description or all key-frames from two descriptions. Experiments showed that, as compared to previous methods, the proposed MDVC control method yielded 1-2 dB higher in image PSNRs for Wyner-Ziv reconstructed frames at the side decoder when encoding low-to-medium complexity videos. For high-complexity videos, it effectively prevents error correction of Wyner-Ziv frames from malfunctioning and yields about 3 dB higher in PSNR. The proposed MDVC central decoder control yields 1-4 dB higher PSNRs, as compared to side decoders. Under lossy transmission, it demonstrates 27-64% smaller PSNR variations, as compared to that of combining key-frames as the decoded video. The proposed MDVC system and control not only improve the DVC reconstructed video quality, but also reduce the quality fluctuation artifacts of MDC coded video for mobile coders.

Combining distributed video coding with super-resolution to achieve H.264/AVC performance

Distributed video coding (DVC) is an emerging video coding paradigm for systems that require low-complexity encoders that are supported by high-complexity decoders as required, for example, in real-time video capture and streaming from one mobile phone to another. Under the assumption of an error-free transmission channel, the coding efficiency of current DVC systems is still below that of the latest video codecs, such as H.264/AVC. In order to increase the coding efficiency, we propose that every Wyner-Ziv frame be downsampled by a factor of two prior to encoding and the subsequent transmission. However, this would necessitate upsampling in conjunction with interpolation at the decoder. Simple interpolation (e.g., a bilinear or bicubic filter) would be insufficient because the high-frequency (HF) spatial image content would be missing. Instead, we propose the incorporation of a super-resolution (SR) technique based upon the example-based scene-specific method to allow this HF content to be recovered. The SR technique will add computational complexity to the decoder side of the DVC system, which is allowable within the DVC framework. Rate-distortion curves show that this novel combination of SR and DVC improves the system's peak signal-to-noise ratio (PSNR) performance by up to several decibels and can actually exceed the performance of the H.264/AVC codec when GOP = IP for some video sequences.

Adaptive Correlation Noise Model for DC Coefficients in Wyner-Ziv Video Coding

An adaptive correlation noise model (CNM) construction algorithm is proposed in this paper to increase the efficiency of parity bits for correcting errors of the side information in transform domain Wyner-Ziv (WZ) video coding. The proposed algorithm introduces two techniques to improve the accuracy of the CNM. First, it calculates the mean of direct current (DC) coefficients of the original WZ frame at the encoder and uses it to assist the decoder to calculate the CNM parameters. Second, by considering the statistical property of the transform domain correlation noise and the motion characteristic of the frame, the algorithm adaptively models the DC coefficients of the correlation noise with the Gaussian distribution for the low motion frames and the Laplacian distribution for the high motion frames, respectively. With these techniques, the proposed algorithm is able to make a more accurate approximation to the real distribution of the correlation noise at the expense of a very slight increment to the coding complexity. The simulation results show that the proposed algorithm can improve the average peak signal-to-noise ratio of the decoded WZ frames by 0.5 dB to 1.5 dB.

분산 동영상 부호화 시스템을 위한 LDPC 부호 설계 및 성능 평가

LDPC(low density parity check) 부호는 낮은 복잡성과 Shannon의 한계에 근접하는 오류 정정 능력을 보이기 때문에 turbo 부호와 함께 많은 응용 분야에 적용되고 있다. 최근에는 분산 동영상 부호화(distributed video coding: DVC) 시스템의 Wyner-Ziv 프레임 복호를 위해서도 LDPC 부호가 많이 사용되고 있다. 본 논문에서는 DVC 시스템을 위한 LDPC 부호를 설계하기 위해 패리티 체크 행렬 H를 설계하고 부호율 적응적인(rate adaptive) 특성을 만족하기 위해 H 행렬의 패리티 점검 노드를 효율적으로 병합하는 방법을 제안한다. 이를 위해 cycle의 연결성을 고려한 ACE(approximation cycles EMD) 알고리즘을 기반으로 효율적인 LDPC 부호를 설계하고 부호율 적응적인 특성을 갖도록 하기 위해 H 행렬의 크기와 압축율을 고려하여 병합 범위를 지정하고 지정된 범위에 따라 패리티 점검 노드를 병합한다. 그리고 ACE 알고리즘의 계수와 차수 분포를 변화시키면서 설계한 LDPC 부호의 성능을 해석한다. Low density parity check (LDPC) code is widely used, since it shows superior performance close to Shannon limit and its decoding complexity is lower than turbo code. Recently, it is used as a channel code to decode Wyner-Ziv frames in distributed video coding (DVC) system. In this paper, we propose an efficient method to design the parity check matrix H of LDPC codes. In order to apply LDPC code to DVC system, the LDPC code should have rate compatibility. Thus, we also propose a method to merge check nodes of LDPC code to attain the rate compatibility. LDPC code is designed using ACE algorithm and check nodes are merged for a given code rate to maximize the error correction capability. The performance of the designed LDPC code is analyzed extensively by computer simulations.

Key frame quantisation error reduction in distributed video coding

Proposed is a post-processing scheme to reduce the quantisation noise of the key frames by using the decoded neighbour Wyner-Ziv frames in a distributed video coding framework. The proposed scheme results in a quality gain of up to 2 dB for the key frames and improves the overall rate-distortion performance of the codec without adding any additional complexity at the encoder.