Video Coding Technique Research Articles

확장 가능한 영상 부호화에서 전 확장성을 고려한 품질 메트릭

다양한 멀티미디어 영상 서비스 환경에 최적의 서비스 품질(Quality of Service, QoS)을 제공하는 것은 중요 이슈 중 하나이다. 이를 위해서 다양한 서비스 환경에 따라 쉽게 확장 가능한 영상 부호화 기술과 영상의 품질을 계량적으로 표현하는 기술이 필요하다. 본 논문에서는 확장 가능한 영상 부호화(Scalable Video Coding, SVC)에 기반한 영상에 대해 영상의 내용 특징 정보와 전 확장성, 즉 시간적, 공간적, 품질적 확장을 고려한 새로운 품질 메트릭을 제안한다. 실험 결과, 제안된 품질 메트릭은 측정된 주관적 점수와의 상관계수(correlation coefficient)가 평균 0.9이상으로 우수한 성능을 증명하였다. 본 논문에서 제안한 메트릭은 영상의 다양한 프레임 율, 화질, 공간 해상도, 그리고 모션 특성과 같은 부호화 조건에 따른 품질측정이 가능하여 최적의 부호화 조건을 결정할 수 있다. Currently, the efficient adaptive video streaming services and coding techniques are required to ensure quality of service (QoS) in diverse multimedia environments. To maintain optimal video quality in these environments, it is required to support scalable video coding (SVC) technique and proper QoS metric methods. In this paper, we propose a new quality metric that takes in to the temporal, the SNR, the spatial scalability on SVC. Experimental results shows that proposed method has a higher correlation with the subjective quality. We expect that the proposed metric plays an important role in deciding the coding parameter to optimize the quality of the SVC based video.

Block Motion Estimation Based on Immune Clonal Selection

Motion estimation is a key technique in video compress and coding. Based on the analysis of the character of motion vector, a novel block motion estimation based on immune clonal selection (BMEICS) is proposed in this paper with some strategies like prediction of initial search point, Gray encoding and effective stop criteria. BMEICS synthesizes the character of block motion estimation and that of global search, diversity, and no prone to premature in immune clonal selection. It speeds up the process of motion estimation while maintaining the average with little loss. Experimental results show that BMEICS obtains almost the same as the full search algorithm with fewer search points, and outperforms the existing fast block-matching algorithms for most sequences in terms of speed and quality. Furthermore, BMEICS is applicable to all types of video sequences in spite of the degree of motion.

Recent advances in rate control for video coding

In this paper, we review the recent advances in rate control techniques for video coding. The rate control algorithms recommended in the video coding standards are briefly described and analyzed. Recent advances, such as new concepts in rate-distortion modelling and quality constrained control, are presented. With these techniques, the rate control performance can be improved. The paper not only summarizes these recent rate control techniques but also provides explicit directions for future rate control algorithm design.

A context adaptive bit-plane coder with maximum-likelihood-based stochastic bit-reshuffling technique for scalable video coding

In this paper, we propose a context adaptive bit-plane coding (CABIC) with a stochastic bit reshuffling (SBR) scheme to deliver higher coding efficiency and better subjective quality for fine granular scalable (FGS) video coding. Traditional bit-plane coding in FGS algorithm suffers from poor coding efficiency and subjective quality. To improve coding efficiency, our CABIC constructs context models based on both the energy distribution in a block and the spatial correlations in the adjacent blocks. Moreover, it exploits the context across bit-planes to save side information. To improve subjective quality, our SBR reorders the coefficient bits by their estimated rate-distortion performance. Particularly, we model transform coefficients with Laplacian distributions and incorporate them into the context probability models for content-aware parameter estimation. Moreover, our SBR is implemented with a dynamic priority management that uses a low-complexity dynamic memory organization. Experimental results show that our CABIC improves the PSNR by 0.5~1.0 dB at medium and high bit rates. While maintaining similar or even higher coding efficiency, our SBR improves the subjective quality

A Novel Adaptive Reception Scheme for Satellite-DMB Systems

The paper proposes an adaptive reception (AR) scheme for S-DMB systems. Layered streams are generated by adopting scalable video coding (SVC) technique to transmit video data hierarchically over broadcasting channel(s). Depending on the terminal's type, the minimum amount of data frames are adoptively received by employing a frame selection control at the receiver. We quantitatively investigate the benefits in terms of power consumption and available viewing time with a case of S-DMB phones.

Multipoint videoconferencing with scalable video coding

We describe a system for multipoint videoconferencing that offers extremely low end-to-end delay, low cost and complexity, and high scalability, alongside standard features associated with high-end solutions such as rate matching and per- sonal video layout. The system accommodates heterogeneous receivers and networks based on the Internet Protocol and relies on scalable video coding to provide a coded representation of a source video signal at multiple temporal and spatial resolutions as well as quality levels. These are represented by distinct bitstream components which are created at each end-user encoder. Depending on the specific conferencing environment, some or all of these components are transmitted to a Scalable Video Conferencing Server (SVCS). The SVCS redirects these components to one or more recipients depending on, e.g., the available network con- ditions and user preferences. The scalable aspect of the video coding technique allows the system to adapt to different network conditions, and also accommodates different end-user requirements (e.g., a user may elect to view another user at a high or low spatial resolution). Performance results concerning flexibility, video quality and delay of the system are presented using the Joint Scalable Video Model (JSVM) of the forthcoming SVC (H.264 Annex G) standard, demonstrating that scalable coding outper- forms existing state-of-the-art systems and offers the right platform for building next-generation multipoint videoconferencing systems.

A quadratic prediction based fractional-pixel motion estimation algorithm for H.264

Motion estimation (ME) and compensation is the most important technique in video coding. In H.264, the motion vector (MV) of a variable size block is determined by performing the ME search procedure on integer-pixel positions, followed by fractional-pixel refinement. For fast integer-pixel ME algorithms, on the average, ME can be done by examining less than 5 search positions. Considering the conventional fractional-pixel ME algorithm, 8, 16, and 24 fractional-pixel search positions are required to be examined for the best MV at 1/2-, 1/4-, and 1/8-pixel accuracy, respectively. That is, the computational complexity of fractional-pixel ME becomes comparable to that of fast integer-pixel ME. Therefore, to develop an efficient fractional-pixel ME algorithm is greatly desirable. In this study, a fast fractional-pixel ME algorithm is proposed. In this study, a “degenerate” quadratic function is used to precisely determine the “best” quantized predictive motion vector (PMV) at 1/4-pixel accuracy for a variable size block. Based on the partial probability distributions of the sum of absolute component differences between the best MV at 1/4-pixel accuracy determined by the conventional 2-stage full search ME search algorithm and the “best” quantized PMV determined by the proposed algorithm, the search range of local fraction-pixel ME can be well determined. If the best quantized PMV determined by the proposed algorithm and that determined by the center biased fractional-pixel search algorithm are identically (0, 0), then (0, 0) is directly determined as the MV at 1/4-pixel accuracy for the variable size block, without applying the small diamond search pattern (SDSP). Otherwise, the SDSP at 1/4-pixel accuracy is used to determine the final result and the SDSP will be applied at most three times. Based on the experimental results obtained in this study, the four ME performance measures of the proposed algorithm are better than that of four comparison approaches, with slight degradations in average PSNR and bit rate.

Layered Video Coding Based on Displaced Frame Difference Prediction and Multiresolution Block Matching

This paper presents a new video-coding technique based on displaced frame difference (DFD) prediction and multiresolution block matching for layered transmission. Starting from the base layer, the algorithm encodes one layer at a time until the design of the top layer is completed. For the encoding of each layer, the DFD prediction and multistage motion-vector quantization (MSMVQ) techniques are employed so that the results of DFD encoding and block matching at previous layers can be used to enhance the coding efficiency at that layer. Numerical results show that the algorithm is effective for the applications where high rate-distortion performance and low computational complexity for layered video transmission are required.

An Integrated Source and Channel Rate Allocation Scheme for Robust Video Coding and Transmission over Wireless Channels

A new integrated framework for source and channel rate allocation is presented for video coding and transmission over wireless channels without feedback channels available. For a fixed total channel bit rate and a finite number of channel coding rates, the proposed scheme can obtain the near-optimal source and channel coding pair, and corresponding robust video coding scheme such that the expected end-to-end distortion of video signals can be minimized. With the assumption that the encoder has the stochastic information such as average SNR and Doppler frequency of the wireless channel, the proposed scheme takes into account robust video coding, channel coding, packetization, and error concealment techniques altogether. An improved method is proposed to recursively estimate the end-to-end distortion of video coding for transmission over error-prone channels. The proposed estimation is about 1-3 dB more accurate compared to the existing integer-pel based method. Rate-distortion optimized video coding is employed for the trade-off between coding efficiency and robustness to transmission errors.

An Experimental Study on the Quality-of-Service of Video Encoded Sequences Over an Emulated Rain-Faded Satellite Channel

Video-coding techniques that are widely used in videoconferencing and streaming applications over the Internet may face degradation in performance when traversing satellite channels. The aim of the present paper is to provide objective measurements of the quality of video-encoded sequences for two of the most popular video coders in this setting [namely, H.261 and moving picture experts group (MPEG)-2], after transmission over faded satellite channels. In particular, the emphasis is on the Ka band, which is becoming an attractive alternative for commercial applications but is more prone to quality degradation than the currently widely used Ku band. In order to test the behavior of the coders in repeatable experimental conditions and over different data link platforms, two transmission chains have been implemented in the laboratory by careful emulation of the required environment. The data link layer has been based on HDLC-like and direct video broadcasting protocols, respectively. The experiments have been performed in the presence of additive white Gaussian noise (AWGN) and by using fading patterns derived by real-world data. The results obtained highlight some often neglected aspects in the behavior of the coders under examination, both in relation to their comparative performance and to their adaptability to different underlying data link protocols.

An effective mesh-based motion compensation technique for video coding

The block-matching algorithm is the most popular motion compensation technique in video coding. However, it cannot provide acceptable quality at very low bit rate. In this paper, a new mesh-based motion compensation method is proposed to attack the problem. First, a regular non-uniform mesh, which has regular structure with variable patch size, is presented. The patch size is varied according to motion activity of a video sequence. Next, a weighted interpolation block matching is developed to improve the estimate accuracy of displacements of grid points. It utilizes the motion correlation between a grid point and its associated patches. Finally, based on the new mesh and motion estimation scheme, an efficient motion compensation algorithm is developed. When compared to the conventional motion compensation techniques, the proposed method improves performance significantly with lower computational complexity and overhead information bits.

Advanced video coding

Advanced video coding techniques will allow broadcasters to improve the efficiency offered by MPEG-2 digital TV systems by up to 75%. The opportunity for significant improvements in MPEG-2 performance is now very limited. MPEG-2 solutions are likely to become more dense, lower power and inexpensive, but they are not going to produce much lower bit rates. It is fortunate that, also during the last ten years, Moore's Law - which states that semiconductor/computer processing power increases by a factor of two every eighteen months - has also progressed relentlessly. More processing power at a lower price has enabled a whole new generation of compression technology. Both set-top boxes and headend equipment are now capable of much more complex calculations at commercially acceptable prices than were possible at the time of MPEG-2 standardisation. The two most significant algorithms/systems proposed currently are Windows Media 9 Series, from Microsoft, and MPEG-4 part 10, an open standards algorithm from the ITU/MPEG Joint Video Team. Both these systems draw heavily on the experience of MPEG-2, but add extra tools to improve the coding efficiency - particularly at low bit rates.

Design of an efficient authentication method for modern image and video

Data origin and data integrity authentication are, very important factors in image and video security. As modern image and video coding techniques become standards, authentication methods should be devised that cope with the modern standards' intrinsic capabilities: scalability and a trend towards more content-oriented compression. So far no efficient authentication system addresses these properties.. The design of an efficient scalable authentication technique under reasonable system considerations is reviewed. The technique addresses modern coding standards such as JPEG2000 and MPEG4. In addition, the authentication method is enhanced by introducing novel cryptographic primitives that further enhance the method's applicability to real-world scenarios.

Real-time foveation techniques for low bit rate video coding

Lossy video compression methods often rely on modeling the abilities and limitations of the intended receiver, the human visual system (HVS), to achieve the highest possible compression with as little effect on perceived quality as possible. Foveation, which is non-uniform resolution perception of the visual stimulus by the HVS due to the non-uniform density of photoreceptor cells in the eye, has been demonstrated to be useful for reducing bit rates beyond the abilities of uniform resolution video coders. In this work, we present real-time foveation techniques for low bit rate video coding. First, we develop an approximate model for foveation. Then, we demonstrate that foveation, as described by this model, can be incorporated into standard motion compensation and discrete cosine transform (DCT)-based video coding techniques for low bit rate video coding, such as the H.263 or MPEG-4 video coding standards, without incurring prohibitive complexity overhead. We demonstrate that foveation in the DCT domain can actually result in computational speed-ups. The techniques presented can be implemented using the baseline modes in the video coding standards and do not require any modification to, or post-processing at, the decoder.

A robust model generation technique for model-based video coding

In conventional model-based coding schemes, predefined static models are generally used. These models cannot adapt to new situations, and hence, they have to be very specific and cannot be generated from a single generic model even though they are very similar. We present a model-generation technique that can gradually build a model and dynamically modify it according to new video frames scanned. The proposed technique is robust to the object's orientation in the view and can be efficiently implemented with a parallel processing technique. As a result, the proposed technique is more attractive to the practical use of model-based coding techniques in real applications.

An efficient low bit-rate video-coding algorithm focusing on moving regions

Block-based motion estimation and compensation are the most popular techniques for video coding. However, as the shape and the structure of an object in a picture are arbitrary, the performance of such conventional block-based methods may not be satisfactory. In this paper, a very low bit-rate video coding algorithm that focuses on moving regions is proposed. The aim is to improve the coding performance, which gives better subjective and objective quality than that of the conventional coding methods at the same bit rate. Eight patterns are pre-defined to approximate the moving regions in a macroblock. The patterns are then used for motion estimation and compensation to reduce the prediction errors. Furthermore, in order to increase the compression performance, the residual errors of a macroblock are rearranged into a block with no significant increase of high-order DCT coefficients. As a result, both the prediction efficiency and the compression efficiency are improved.

Subband video coding with scene-adaptive hierarchical motion estimation

This paper presents a new motion-compensated subband video-coding technique using variable reference-frame positions for motion estimation. The work builds on temporal segmentation for determining the reference-frame positions and incorporates multiresolution motion estimation in the subband domain. The key advantage of the new algorithm is the complexity reduction in motion estimation that uses the multiresolution property of subband decomposition. Temporal segmentation is performed with the lowest spatial subband, based on the detection of two types of scene change. The frames of input video are split into seven spatial subbands, and the motion vectors for each subband are generated by a hierarchical motion-estimation algorithm. Blockwise differential pulse code modulation (DPCM) and a uniform quantizer are used for the lowest subband of the first frame only, and the subbands of all other cases are coded by PCM with a dead zone quantizer. Simulation results show that our scene-adaptive scheme compares favorably with a fixed interpolation structure.

A coding technique for the contours in smoothly perfect eight-connectivity based on two-stage motion compensation

In this paper, a new contour-coding technique for object-oriented video coding is proposed, In our approach, the two-stage motion compensation technique is considered, in order to cope with the rather complex motion of the object. While the object-based motion compensation is performed in the first stage, the second-stage motion compensation is carried out to search the best match of the contours, which are not motion compensated in the first stage. Also by introducing the notion of the error band, the current contours can be properly fitted to the motion compensated contours using the interframe relationship of the contours. In addition, an efficient technique for encoding the contours, simplified by the majority filter, is also proposed. From the simulation result, it is shown that the proposed technique provides better performance than the content-based arithmetic encoding, especially when lossy encoding is allowed. Moreover, by varying the width N of the error band, it is shown that the bit amount for the shape information can be adjusted according to the channel condition.

Very low bit-rate video coding using cellular neural network universal machine

A method of video coding for very low bit-rate channels, which is implemented using cellular neural network universal machine, is presented in the following paper. The presented method combines elements of a standard approach to video coding with elements of second-generation video-coding techniques. Inter-frame coding is performed using standard block-based motion estimation procedure, while intra-frame coding is based on vector quantization approach. To satisfy constraints imposed by very low bit-rate channel throughput, a number of bytes that were considered to be used for representing video sequence frames, was assumed to be less than 200. Simulations of the algorithm execution, based on actual CNN UM chip parameter values, show feasibility of using the proposed method for real-time implementation of very low bit-rate video coding.

Extensions of ITU-T recommendation H.324 for error-resilient video transmission

The authors provide an overview of techniques that enable the use of ITU-T recommendation H.324 with error-prone transmission channels. H.324 covers the overall architecture, algorithms, and syntax for low-bit-rate multimedia terminals. This overview focuses on extensions for error-resilient video transmission that are related to the H.263 video codec and H.223 multiplex. The latter is responsible for reliable delivery of data to each terminal component and is therefore of major importance to the overall system. In particular, the discussed approaches to robust video transmission require reliable performance of the multiplex scheme. The considered techniques for video coding are either compatible with the baseline mode of H.263 or part of new extensions recently devised by Study Group 16 as part of the H.263+ effort. This overview includes "error tracking" (Appendix II). "reference picture selection" (Annex N), and "independent segment decoding" (Annex R). Whenever appropriate, the description of those video extensions and multiplex schemes is complemented with simulation results for transmission over Rayleigh fading channels.