A new error concealment algorithm for H.264 video transmission

In the new video coding standard H.264/AVC, motion estimation (ME) is allowed to search multiple reference frames. Therefore, the required computation is highly increased, and it is in proportion to the number of searched reference frames. However, the reduction in prediction residues is mostly dependent on the nature of sequences, not on the number of searched frames. Sometimes the prediction residues can be greatly reduced, but frequently a lot of computation is wasted without achieving any better coding performance. In this paper, we propose a context-based adaptive method to speed up the multiple reference frames ME. Statistical analysis is first applied to the available information for each macroblock (MB) after intra-prediction and inter-prediction from the previous frame. Context-based adaptive criteria are then derived to determine whether it is necessary to search more reference frames. The reference frame selection criteria are related to selected MB modes, inter-prediction residues, intra-prediction residues, motion vectors of subpartitioned blocks, and quantization parameters. Many available standard video sequences are tested as examples. The simulation results show that the proposed algorithm can maintain competitively the same video quality as exhaustive search of multiple reference frames. Meanwhile, 76 %-96 % of computation for searching unnecessary reference frames can be avoided. Moreover, our fast reference frame selection is orthogonal to conventional fast block matching algorithms, and they can be easily combined to achieve further efficient implementations.

H.264 adopts new coding tools such as variable block size, quarter-pixel-accuracy motion estimation/compensation, multiple reference frames, loop filter, etc. The adoption of these tools enables a macroblock to have more information compared with previous standards. In H.264 each macroblock can have up to sixteen motion vectors, four reference frames, and a mode of the macroblock, all of which can be used for temporal error concealment. The H.264 error concealment in the informative part, however, uses a similar method to prior coding standards that consider only motion vectors of macroblocks adjacent to the lost macroblock. In this paper, we propose an effective temporal error concealment algorithm for H.264-coded video. It uses not only motion vectors and reference frames but the modes of macroblocks adjacent to the lost macroblock as well. Depending on the modes of neighboring macroblocks, each lost macroblock is concealed on the basis of different block sizes. Simulation results show the proposed method yields better video quality than conventional approaches.

H.264/AVC, the latest video coding standard, adopts rate-distortion optimization (RDO) technique to obtain the best intra- and inter-prediction, while maximizing visual quality and minimizing the required bitrate. However, the full RD cost calculation for all intra-prediction modes, the exhaustive searches for finding optimal motion vectors for all block sizes, and the multiple references frame procedure considerably increase its computational complexity with the allowed number of prediction modes. The authors have previously proposed an approach for both inter- and intra-mode decisions that takes into account the several effective parameters, image content type, quantization parameter, correlation of motion vectors and motion details of video objects. In order to reduce the complexity, here we propose a new two-step adaptive search range decision by developing a combination of previous algorithm. The first step of our adaptive search range decision determines the search range for current MB according to the motion vectors of the previous MBs. In the second step, the motion vector obtained in the current frame is used to adaptively searching the window size of the previous reference frame for multi-frame motion estimation. As such, only a subset of inter- and intra-modes is chosen for RDO calculation. Experimental results show that the proposed algorithm reduces the total encoding cost with negligible loss in PSNR and a slightly increase in the required bitrate, when compared to our previous algorithm and other algorithms reported in the literature.

In H.264/AVC standard, motion estimation can be processed on multiple reference frames (MRF) to improve the video coding performance. For the VLSI real-time encoder, the heavy computation of fractional motion estimation (FME) makes the integer motion estimation (IME) and FME must be scheduled in two macro block (MB) pipeline stages, which makes many fast MRF algorithms inefficient for the computation reduction. In this paper, two algorithms are provided to reduce the computation of FME and IME. First, through analyzing the block's Hadamard transform coefficients, all-zero case after quantization can be accurately detected. The FME processing in the remaining frames for the block, detected as all-zero one, can be eliminated. Second, because the fast motion object blurs its edges in image, the effect of MRF to aliasing is weakened. The first reference frame is enough for fast motion MBs and MRF is just processed on those slow motion MBs with a small search range. The computation of IME is also highly reduced with this algorithm. Experimental results show that 61.4%-76.7% computation can be saved with the similar coding quality as the reference software. Moreover, the provided fast algorithms can be combined with fast block matching algorithms to further improve the performance.

Motion Estimation (ME) is the most computationally intensive part of video compression systems. Multiple reference frame (MRF) ME used in H.264 standard increases the video coding efficiency at the expense of increased computational complexity and power consumption. Therefore, in this paper, we present a reconfigurable baseline H.264 video encoder hardware in which the number of reference frames used for MRF ME can be configured based on the application requirements in order to trade-off video coding efficiency and power consumption. The proposed H.264 video encoder hardware is based on an existing low cost H.264 intra frame coder hardware and it includes new reconfigurable MRF ME, mode decision and motion compensation hardware. The proposed H.264 video encoder hardware is capable of processing 55 CIF (352×288) frames per second and its power consumption ranges between 115mW and 235mW depending on the number of reference frames used for MRF ME.

This paper presents a novel block matching scheme with edge alignment strategy on H.264 video coding, which uses multiple references and multiple block sizes for motion estimation in order to improve the rate-distortion performance. In H.264, the computational complexity is linearly dependent on the number of allowed reference frames and block sizes using the full exhaustive search. Many fast block-matching algorithms reduce the computational complexity of motion estimation by carefully designing the search patterns with different shapes or sizes which have significant impact on the search speed and distortion performance. However, the search speed and the distortion performance conflict often with each other for these methods. In this paper, given a block in the current frame, we first apply a fast approximate method based on edge alignment to obtain a good initial motion vector as well as a tight initial bound of distortion measure. Then, considering the edge orientation of the block, a modified hexagon search is used to fine tune the motion vector in low computational complexity. The proposed algorithm also pays attentions to the characteristics of multiple reference frames and multiple block sizes in H.264. Computer simulation results show that the proposed method gives good performance and spans a new way to design a cost-effective real-time video coding system

In this research work, a multiple synchronous reference frame (MSRF) based analysis method used together with exponential smoothing (ES) to accurately obtain the time-varying harmonics and interharmonics of electric arc furnace (EAF) currents, is proposed. The proposed method has been implemented on NVIDIA Geforce GTX 960 graphics card for the parallel processing of all harmonics and interharmonics so that real-time processing of the EAF currents obtained from a measurement point of the electricity transmission system is possible. To obtain the best possible accuracy for the EAF current harmonics and interharmonics estimation, the ES window size has been optimized specific to each harmonic and interharmonic frequency component. It has been shown on field data that the implemented system is capable of successfully estimating all harmonics up to the 50th and all interharmonics at 5Hz resolution in real-time. Moreover, active filtering of certain harmonics and interharmonics has been achieved in the simulation environment and it has been shown that successful real-time filtering of any harmonic and interharmonic component is possible with the proposed MSRF+ES method. Hence, it can be concluded that the proposed system can be used to generate reference signals for the controllers of the new technology compensation systems such as active power filters.

For permanent magnet synchronous machines (PMSMs), current harmonics need to be controlled under two kinds of conditions. Under the first condition, the current harmonics caused by the non-sinusoidal back-electromotive force (EMF) and the dead time of inverters should be suppressed. Under the second condition, specific current harmonics should be injected to suppress the torque ripple of motors. Therefore, the accurate control of current harmonics is critical. It has been found that the original multiple reference frame (MRF)-based control algorithm cannot effectively achieve the control of current harmonics at high speeds. For the currents in MRFs, motional EMF was dominant rather than induced EMF at higher speeds. As a result, the original MRF-based control algorithm does not work at high speeds. To solve this problem, this paper proposed a novel MRF-based control algorithm that considers motional EMF. Furthermore, this paper achieved decoupling control of the current harmonics in MRFs for interior PMSMs. With the proposed control algorithm, the current harmonics of interior PMSMs can be controlled at both high and low speeds. Under the influence of non-sinusoidal back EMF and the dead time of the inverter, the effect of current harmonic control was verified on a laboratory test bench.

This paper presents a bidirectional motion estimation (ME) method based on tracking feature trajectories and compensating for occlusion to enhance the temporal resolution of an input video sequence. First, we extract features and estimate their trajectories in the forward direction. We continue to track features only if the reliability of their trajectory is sufficiently high. Accordingly, if a feature can be continuously tracked through multiple frames, the proposed method assumes that its trajectory is a true motion vector (MV). Then, these forward feature trajectories are used as reference motion directions for backward block-based ME. If a block does not include any feature trajectories, we use the MVs of neighboring blocks as candidate MVs to propagate the predetermined true MV and preserve the spatial correlation of MVs. Further, the proposed method can detect occlusion regions, where a continuously tracked feature does not have a corresponding point in the current frame. In the detected occlusion region, the intermediate frame is generated from either the previous frame or the current frame. Outside the occlusion region, we generate the intermediate frames by taking into consideration the neighboring MVs to reduce blocking artifacts. Experimental results show that the proposed temporal frame interpolation (TFI) method can improve visual quality over conventional TFI methods, both objectively and subjectively.

It has been previously suggested to use multiple reference frame (MRF) structures, based on proportional-integral controllers in synchronous reference frames (SRFs), to suppress current harmonics caused by nonlinearities in multiphase drives. However, the rotational transformations are computationally demanding. In Part 1, the three-phase strategy based on resonant controllers (RCs) implemented in an SRF has been extended to any phase number. Nevertheless, while the computational burden of MRF and multiple RC (MRC) schemes has been assessed for three-phase systems in previous papers, it is yet to be studied for other numbers of phases. Part 2 analyzes the computational load of the MRC and MRF strategies as a function of the phase number and of the highest harmonic order to be compensated. It is proved that the former provides a resource saving with respect to the latter that decreases with the phase number and increases with the highest harmonic order under consideration. It is also concluded that the MRC strategy is particularly preferable in machines with even phase number (e.g., a multiple of six).

Motion estimation using multiple reference frames is widely used as the basis for recent video coding standards (eg. H.264/AVC) to achieve increased coding efficiency. However, this increases the complexity of the encoding process. In this paper, a new technique for efficient motion estimation is proposed. A combination of multiple reference frame selection and image residue-based mode selection is used to improve motion estimation time. By dynamic selection of an initial reference frame in advance, the number of reference frames to be considered is reduced. In addition, from examination of the residue between the current block and reconstructed blocks in preceding frames, variable block size mode decisions are made. Modified initial motion vector estimation and early stop condition detection are also adopted to speed up the motion estimation procedure. Experimental results compare the performance of the proposed algorithm with a state of the art motion estimation algorithm and demonstrate significantly reduced motion estimation time while maintaining PSNR performance.

Fast reference frame selection based on content similarity for low complexity HEVC encoder

In this work, CFD simulations have been conducted to investigate flow behaviour of water in fully baffled stirred tank with Rushton turbine as impeller. The aim of the paper is to develop CFD model of such tank and optimize the dimensions of inner rotating fluid zone for MRF model. The best inner rotating fluid zone is found when the simulation results for mean radial velocity, mean tangential velocity and mean axial velocity are reasonably matched with literature data of Wu and Patterson (1989). The global flow parameters such as flow number and power number predicted by CFD matched quite well with the data of Wu and Patterson (1989) and Rushton et al. (1950). The developed CFD model is able to predict key phenomenon of circulating loops inside the stirred tank. The trend of turbulence energy dissipation rate obtained from CFD simulations is in good agreement with the literature data of Wu and Patterson (1989). Abbreviations: CFD: Computational Fluid Dynamics; LDA: Laser Doppler Anemometry; PIV: Particle Image Velocimetry; LSI: Laser Sheet Illumination; MRF: Multiple Reference Frame; RANS: Reynolds averaged Navier–Stokes; LES: Large Eddy Simulation; DNS: Direct Numerical Simulation; SIMPLE: Semi Implicit Method for Pressure Linked Equations; RMSE: Root Mean Squared Error; PRESTO: Pressure Staggering Option

Event Abstract Back to Event Multiple representations of touch Christoph Braun1*, Luigi Tamè2, Christos Papadelis1, Alessandro Farnè2 and Francesco Pavani2 1 CIMeC Center for Mind/Brain Sciences, University of Trento, Italy 2 INSERM U1028, CNRS UMR5292, Lyon Neuroscience Research Centre, France Touch is represented in multiple reference frames in the brain. On an early level of processing, tactile input is coded in a somatotopic frame preserving the neighborhood relation of adjacent skin areas. On higher levels, touch is represented in references frames related to limb function, body orientation and external space. The goal of the present study was to infer the anatomical substrate for different reference frames using functional neuroimaging. Assuming that the processing of a stimulus is affected by a distracter stimulus as long as they share a common representation, the brain areas for different reference frames can be identified by their interaction. Here, left index finger served as target location. Tactile distracters were applied to the left and right middle and index fingers with a stimulus onset asynchrony (SOA) of 0, 25 and 125 ms. Activation of left and right primary (SI) and secondary somatosensory (SII) cortex could be identified using neuromagnetic source imaging. On the level of SI, no effect of distracters applied to the other hand was found. Yet, SII responses to the target stimulus were diminished by stimulating fingers of the other hand. The reduction was stronger for stimulation of the non-homolog than the homolog finger. Increasing SOAs between distracters and target stimuli revealed that SII responses to the target were delayed by the previously applied distracter only for the SOA of 125 ms. Results indicate that on the level of SII, there exist shared representations integrating information from homologous regions of the left and right half of the body implying a common reference frame for homolog limbs. Effects of SOA suggest that SII is involved in the analysis of the temporal structure of the stimuli. Keywords: Sensation, SII Conference: XI International Conference on Cognitive Neuroscience (ICON XI), Palma, Mallorca, Spain, 25 Sep - 29 Sep, 2011. Presentation Type: Poster Presentation Topic: Poster Sessions: Neurophysiology of Sensation and Perception Citation: Braun C, Tamè L, Papadelis C, Farnè A and Pavani F (2011). Multiple representations of touch. Conference Abstract: XI International Conference on Cognitive Neuroscience (ICON XI). doi: 10.3389/conf.fnhum.2011.207.00479 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 Nov 2011; Published Online: 28 Nov 2011. * Correspondence: Dr. Christoph Braun, CIMeC Center for Mind/Brain Sciences, University of Trento, Trento, Italy, christoph.braun@uni-tuebingen.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Christoph Braun Luigi Tamè Christos Papadelis Alessandro Farnè Francesco Pavani Google Christoph Braun Luigi Tamè Christos Papadelis Alessandro Farnè Francesco Pavani Google Scholar Christoph Braun Luigi Tamè Christos Papadelis Alessandro Farnè Francesco Pavani PubMed Christoph Braun Luigi Tamè Christos Papadelis Alessandro Farnè Francesco Pavani Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Oxidation ditches (OD) are one of the most common aeration units or bioreactors in the activated sludge process. Flow and hydrodynamic characteristics play an important role in successful operation of an OD. It is difficult to study the rheology in a detailed way because it’s time-consuming and expensive. However, due to the development of computational fluid dynamics (CFD), such a study has become easier and less expensive. CFD is a powerful tool to simulate the hydrodynamics. Since in mixing operations, the generation of fluid flow is due to the input of mechanical energy in form of rotation of the impeller, the one of very important consideration is the choice of a model that describes impeller rotation. The flow features associated with multiple rotating parts can be analyzed using the multiple reference frame (MRF) capability. Based on previous studies on OD in the field of wastewater treatment (few numbers has been done) there is no direct mention of the size of rotating zone for the simulation so a fundamental analysis is required and can be helpful for further studies in this field. In this study the effect of rotating zone dimensions on the accuracy of oxidation ditch simulation has been analyzed and four model of moving frame have been set and simulated. Based on the analysis the bigger the radius of rotating zone is the higher the accuracy of modelling is. Moreover, the rotating zone in multiple reference approach cannot be semi-circle.