Candidate Modes Research Articles

H.264/SVC Mode Decision Based on Optimal Stopping Theory

Fast mode decision algorithms have been widely used in the video encoder implementation to reduce encoding complexity yet without much sacrifice in the coding performance. Optimal stopping theory, which addresses early termination for a generic class of decision problems, is adopted in this paper to achieve fast mode decision for the H.264/Scalable Video Coding standard. A constrained model is developed with optimal stopping, and the solutions to this model are employed to initialize the candidate mode list and predict the early termination. Comprehensive simulation results are conducted to demonstrate that the proposed method strikes a good balance between low encoding complexity and high coding efficiency.

Low Complexity H.264/AVC Intraframe Coding for Wireless Multimedia Sensor Network

For the Wireless Multimedia Sensor Network (WMSN), the intraframe video coding is widely used for the robust transmission and computation complexity. Though the intraframe algorithm requires much smaller computational complexity than the interframe coding, the amount of computation of the intraframe should be reduced to use WMSN application. In this paper, we propose an intra mode decision algorithm to reduce the computation complexity of intraframe H.264/AVC encoders. The proposed algorithm determines the candidate modes and skips the remaining modes based on the smoothness and directional similarity of MB. The simulation results show that the proposed algorithm achieves 18% to 70% reduction in the computational complexity, compared with the various conventional methods..

Fast feature-based mode decision for 4×4 intra prediction in H.264/AVC

Intra coding in H.264/AVC can significantly improve the compression efficiency at the cost of high computational complexity due to the use of the rate-distortion optimization technique. To reduce the complexity of intra prediction, we propose a feature-based mode decision algorithm for 4×4 intra prediction. This algorithm is motivated by the fact that a good prediction mode usually has a small residue block, which is the difference between the original block and predicted block. The sum of the absolute transformed coefficients and deviation information of residue block are used to measure the distortion of prediction mode and the smoothness of residue block, respectively. According to the ranking of these two features of all possible modes, and together with the most probable mode, small numbers of candidate modes can be determined. Moreover, the candidate modes are further reduced to only one by using two early termination rules based on the correlation of rank and most probable mode. Simulation results demonstrate that the proposed mode decision method reduces about 60% of total encoding time of intra coding with negligible loss of coding performance.

High-speed inter-view frame mode decision procedure for multi-view video coding

With the amazing development of visual identification systems, multi-view video which is one of the main types of three-dimensional (3D) video signals, captured by a set of video cameras from various viewpoints, has attracted much interest recently. The multi-view video coding (MVC) uses the joint multi-view video model (JMVM) established on H.264/AVC as the core codec to achieve excellent coding efficiency. However, the concomitant problem is the huge encoding complexity especially due to the heavy Rate-to-Distortion Cost (RDCost) computational load of the mode decision (MD) process, which limits the applications of MVC for mobile terminals and embedded systems. In this paper, a high-speed MD (HSMD) algorithm is proposed for the inter-view frames of multi-view video signal. The redundant candidate modes of each macroblock (MB) in the inter-view frames are eliminated to reduce the original RDCost computational load by utilizing multiple efficiency parameters. The quantitative analysis verifies our proposal in theory and the simulation results show that the proposed HSMD algorithm can reduce the encoding time by over 90% for the inter-view video frames with negligible quality loss compared with the original JMVM codec. The proposed algorithm can be widely employed for real-time multi-view signal encoding especially under the mobile and embedded environments to realize the real-time encoding process.

A Modal Approach to Tuning and Bandwidth Enhancement of an Electrically Small Antenna

We describe the physical phenomena that contribute to the behavior of an electrically small TM10 antenna using characteristic mode theory. The application of characteristic modes to antenna tuning and bandwidth enhancement serves as demonstration of the broad utility of the modal technique. A modal analysis of the TM10 antenna's impedance match yields several interesting observations as to the nature of resonances and antiresonances, which has implications for the impedance matching of small antennas in general. Furthermore, to overcome the bandwidth limitations inherent in small antennas, we determine that multiple resonances must be combined and use a conductance ratio as a figure of merit for design. We then investigate the TM10 antenna's potential for multiresonant operation by examining different candidate modes. Using the appropriate characteristic modes to form multiple resonances, we show how the bandwidth of the TM10 antenna can be designed to be nearly double that expected from the physical limit for a single resonance.

Analysis of Fracture in Aluminum Joints Bonded with a Bi-Component Epoxy Adhesive

Abstract Adhesive bonding is a viable alternative to traditional joining systems (e.g., riveting or welding) for a wide class of components belonging to electronic, automotive, and aerospace industries. However, adhesive joints often contain flaws; therefore, the development of such technology requires reliable knowledge of the corresponding fracture properties. In the present paper, the candidate mode I fracture toughness of aluminum/epoxy joints is determined using a double cantilever beam fracture specimen. A proper data reduction scheme for fracture energy calculation has been selected based on the results of a sensitivity analysis. Furthermore, a scanning electron microscope is used in order to explore the locus of failure. Finally, the experimental findings are assessed by means of numerical simulations of crack growth carried out using a cohesive zone model.

Cycling and the city: A case study of how gendered, ethnic and class identities can shape healthy transport choices

As a form of ‘active transport’, cycling has been encouraged as a route to improving population health. However, in many high-income countries, despite being widely seen as a ‘healthy’ choice, few people do cycle for transport. Further, where cycling is rare, it is not a choice made equally across the population. In London, for instance, cycling is disproportionately an activity of affluent, White, men. This paper takes London as a case study to explore why the meanings of cycling might resonate differently across urban, gendered, ethnic and class identities. Drawing on qualitative interview data with 78 individuals, we suggest first that the relative visibility of cycling when few do it means that it is publicly gendered in a way that more normalised modes of transport are not; conversely, the very invisibility of Black and Asian cyclists reduces their opportunities to see cycling as a candidate mode of transport. Second, following Bourdieu, we argue that the affinities different population groups have for cycling may reflect the locally constituted ‘accomplishments’ contained in cycling. In London, cycling represents the archetypal efficient mode for autonomous individuals to travel in ways that maximise their future-health gain, and minimise wasted time and dependence on others. However, it relies on the cultivation of a particular ‘assertive’ style to defend against the risks of road danger and aggression. While the identities of some professional (largely White) men and women could be bolstered by cycling, the aesthetic and symbolic goals of cycling were less appealing to those with other class, gendered and ethnic identities.

A Low Complexity Mode Decision Method for Spatial Scalability Coding

In this paper, a fast mode decision method for the spatial higher layers (SHLs) in scalable video coding (SVC) is proposed based on coding dependency between two adjacent spatial lower and higher layers. The proposed fast mode decision method detects zero motion and zero transform coefficient blocks in the current spatial layer using the already encoded information of the corresponding blocks from the lower layer. The information for zero motion vectors and zero transform coefficients is used to induce a reduced set of candidate modes in SHLs of SVC, which reduces the computation complexity up to about 75% of the total encoding time while maintaining the coding performance with negligible amounts of degradation in peak signal-to-noise ratio values and bitrates.

Mode Decision Strategy for I-Frames in H.264/AVC Based on Low-Pass Filter

For the purpose of reduce the complicated process of H.264/AVC standard, the overall coding flow is studied, and some of the key technolies are discussed in the front part of this thesis. An algorithm for determining the distortion for different data partitions in H.264/AVC is proposed. A low-pass filter is implemented for each macroblock; after the macroblock is smoothed by this filter we compare the result of the filtered macroblock with the original data and generate the difference between them. Then the basic candidate-mode class is determined based on the difference, and the further mode decision can be made within this sub-class. So that the number of candidate modes is reduced, and the complexity of I-frame mode decision process is reduced.

Comprehensive scheme for subpixel variable block-size motion estimation

Fast variable block-size motion estimation is a key issue for real-time applications of the H.264, whereas the subpixel refinement takes up much computational time as compared to integer-pixel mo- tion estimation. We propose a new fast subpixel precision variable block-size motion-estimation scheme. This algorithm uses the sta- tistical information, which comes from the motion activities of the macroblocks (MBs) in the previous frame, to predict the character- istics of MBs in the current frame. Additionally, the distortion values and motion vectors of MBs in the previous frame are also considered as prior knowledge, based on which we can make decisions on early mode selection and early termination, and on whether or not to skip some candidate modes and candidate checking points. The interme- diate results of subpixel motion estimation are used together with the prior knowledge to reduce subpixel search time when searching for stationary blocks. Our new directional information strategy is used in both integer-pixel motion estimation and subpixel motion estima- tion to accelerate the search procedure. Moreover, our algorithm can eliminate the subpixel motion estimation of all the unselected sub- partition modes. The computational resources can then be spent on the modes and locations that deserve to be searched more than oth- ers. Extensive experimental is been done, the results of which show that the speed of our approach is nearly five times that of the fast algorithms in H.264 JM, with a better peak signal-to-noise ratio and better bit performance. © 2011 SPIE and IS&T. (DOI: 10.1117/1.3553438)

General Architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC Intra Frame Transcoding

The latest international video-coding standard H.264/AVC significantly achieves better coding performance compared to prior video coding standards such as MPEG-2 and H.263, which have been widely used in today's digital video applications. To provide the interoperability between different coding standards, this paper proposes an efficient architecture for MPEG-2/H.263/H.264/AVC to H.264/AVC intra frame transcoding, using the original information such as discrete cosine transform (DCT) coefficients and coded mode type. Low-frequency components of DCT coefficients and a novel rate distortion cost function are used to select a set of candidate modes for rate distortion optimization (RDO) decision. For H.263 and H.264/AVC, a mode refinement scheme is utilized to eliminate unlikely modes before RDO mode decision, based on coded mode information. The experimental results, conducted on JM12.2 with fast C8MB mode decision, reveal that average 58%, 59% and 60% of computation (re-encoding) time can be saved for MPEG-2, H.263, H.264/AVC to H.264/AVC intra frame transcodings respectively, while preserving good coding performance when compared with complex cascaded pixel domain transcoding (CCPDT); or average 88% (a speed up factor of 8) when compared with CCPDT without considering fast C8MB. The proposed algorithm for H.264/AVC homogeneous transcoding is also compared to the simple cascaded pixel domain transcoding (with original mode reuse). The results of this comparison indicate that the proposed algorithm significantly outperforms the mode reuse algorithm in coding performance, with only slightly higher computation.

Spatial error concealment with sequence-aligned texture modeling and adaptive directional recovery

A spatial error concealment technique based on the sequence-aligned texture modeling and the adaptive directional recovery is proposed in this work. The sequence alignment technique captures the local variation and the global trend of image textures with surrounding uncorrupted pixels, and provides the best texture model under a given cost function. With the derived texture model, geometric interpolation is used to recover lost pixels adaptively based on pixel locations. There are four candidate modes of pixel sequences to recover lost pixels, and one of them is selected for the concealment purpose. The selection criterion is based on the texture pattern modes of surrounding uncorrupted blocks. The pixel sequences used for error concealment can be obtained from the computation of the decoder or the side information from the encoder. Extensive experimental results are given to demonstrate that our error concealment technique outperforms several benchmark methods in both objective and subjective tests.

Complexity scalable control algorithm for intra coding in H.264 under energy constraints

In this paper, the complexity of intra coding is first analyzed so as to achieve a weight of complexity measurement for each intra mode. Then, a new complexity scalable control algorithm for intra coding in H.264 is proposed, based on the rearrangement of the order of candidate modes and an efficient complexity allocation and control ( CAAC ) scheme at the macroblock ( MB ) level. The candidate modes of each MB are rearranged according to the local-edge information. Experimental results show that our proposed algorithm can make an appropriate cut-off point of the candidate modes sequence adaptively according to the current energy condition of a mobile device, so as to adjust the complexity at any level while maximizing the video quality, which can prolong the operational lifetime of the battery with minimum degradation in video quality.

An Efficient VLSI Architecture for Transform-Based Intra Prediction in H.264/AVC

In this paper, an efficient mode decision algorithm and a high throughput hardware architecture with eight-pixel parallelism for improving the H.264/advanced video coding intra coding efficiency are proposed. Based on the inherent features of the discrete cosine transform, the input block is first transformed and then analyzed to determine its texture directional tendency. A few candidate modes are chosen for cost calculation, which adopts the error model in the sum of absolute integer-transformed differences (SAITD). Experimental results show that the proposed intra prediction algorithm has lower peak signal-to-noise ratio degradation and bit-rate increment compared to other recent designs. Using the SAITD technique, the proposed mode decision algorithm is effectively integrated into intra prediction rather than being a preprocessing unit. For hardware implementation, the proposed intra prediction algorithm in the macroblock level is implemented for prediction computation, mode decision, and reconstruction loop units. The synthesis results show that the proposed architecture can achieve a 100 MHz operation frequency, allowing it to easily support the real-time requirements for video resolutions of up to the 16 source input format.

Hierarchical Intra Mode Decision for H.264/AVC

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The intra mode prediction via exhaustive mode decision exploited in the H.264/advanced video coding effectively improves the coding efficiency, but at the expense of yielding higher computational complexity. In this letter, a fast intra mode decision algorithm, called the hierarchical intra mode decision (HIMD), is proposed to speed up the mode decision process by reducing the number of modes required to be checked for each macroblock. The novelty of the proposed HIMD algorithm lies at the following accounts. 1) An early decision with adaptive thresholding is developed for the mode decision of the luma component. 2) The candidate modes are selected according to their Hadamard distances and prediction directions. 3) Only one of the hierarchical paths will be chosen to compute its least rate-distortion cost. Experimental results have shown that the proposed HIMD algorithm achieves a reduction of 85.75% computational complexity on average, while incurring only 0.164 dB loss in peak signal-to-noise ratio (PSNR) and 2.336% increment on the total bit rate compared with that of exhaustive mode decision, which is a default approach set in the joint model reference software. </para>

Fast mode decision for MPEG-4 AVC/H.264 using spatiotemporal correlation of mode and cost

The best performance in compression efficiency is provided by MPEG-4 AVC/H.264 but at the cost of high computational complexity to select the best mode during the mode decision process. To reduce this complexity, we propose a fast mode decision algorithm that exploits the spatiotemporal correlation of the macroblock (MB) modes and the rate-distortion (RD) costs from the previous and current frames. The proposed method determines the candidate modes for the current MB based on the modes of the four spatially neighboring and temporally collocated MBs. It also incorporates the RD costs of the four reference MBs and the current MB. The experimental results show that the AVC/H.264 encoder using our proposed method achieves about 73% speedup (up to 86.5%) compared to the AVC/H.264 JM 11.0 encoder while preserving a 0.25% increment in total encoding bits with a loss of only 0.09 dB in peak SNR.

Fast Context-Adaptive Mode Decision Algorithm for Scalable Video Coding With Combined Coarse-Grain Quality Scalability (CGS) and Temporal Scalability

To speed up the H.264/MPEG scalable video coding (SVC) encoder, we propose a layer-adaptive intra/inter mode decision algorithm and a motion search scheme for the hierarchical B-frames in SVC with combined coarse-grain quality scalability (CGS) and temporal scalability. To reduce computation but maintain the same level of coding efficiency, we examine the rate-distortion (R-D) performance contributed by different coding modes at the enhancement layers (EL) and the mode conditional probabilities at different temporal layers. For the intra prediction on inter frames, we can reduce the number of Intra4×4/Intra 8×8 prediction modes by 50% or more, based on the reference/base layer intra prediction directions. For the EL inter prediction, the look-up tables containing inter prediction candidate modes are designed to use the macroblock (MB) coding mode dependence and the reference/base layer quantization parameters (Qp). In addition, to avoid checking all motion estimation (ME) reference frames, the base layer (BL) reference frame index is selectively reused. And according to the EL MB partition, the BL motion vector can be used as the initial search point for the EL ME. Compared with Joint Scalable Video Model 9.11, our proposed algorithm provides a 20× speedup on encoding the EL and an 85% time saving on the entire encoding process with negligible loss in coding efficiency. Moreover, compared with other fast mode decision algorithms, our scheme can demonstrate a 7-41% complexity reduction on the overall encoding process.

Complexity scalable control for H.264 motion estimation and mode decision under energy constraints

The H.264 video coding standard supports several inter-prediction coding modes using variable block sizes. The robust rate–distortion optimization (RDO) technique of both the motion estimation (ME) and the mode decision (MD) is adopted to achieve superior coding efficiency, which also entails a lot of complex computations. In this paper, by rearranging the order of candidate modes and using two new rate–distortion–complexity optimization (RDCO) functions, a more efficient RDCO framework for fast ME and MD is first proposed. Then, with this new framework, a novel complexity scalable control algorithm for H.264 inter-prediction coding is devised, which is based on an efficient complexity allocation and control (CAAC) scheme performed both at the frame level and the macroblock (MB) level. Experimental results show that our proposed algorithm can adaptively determine an appropriate cut-off point for a sequence of re-ordered candidate modes according to the current energy condition of a mobile device, which can adjust the complexity of inter-prediction coding to any appropriate level with minimum degradation in video quality. This can therefore prolong the operational lifetime of batteries.

Fast Mode Decision Using All-Zero Block Detection for Fidelity and Spatial Scalable Video Coding

In scalable video coding (SVC) as an extension of H.264/advanced video coding (AVC), a computationally expensive exhaustive mode decision is employed to select the best coding mode for each macroblock (MB). In order to reduce computational complexity, we propose a fast mode decision algorithm for SVC which uses an all-zero block (AZB) detection. Based on the empirical analysis of the inter-layer correlation of the AZB, the MB at the enhancement layer (EL) is predicted whether to be the AZB. Then, only predicted MBs are examined by the AZB detection algorithm. Since the mode decision can be terminated by detecting the AZB, we determine the processing order of the candidate modes at the EL in order to terminate the mode decision in the early stage. The proposed algorithm can be combined with other conventional fast mode decision methods in order to further reduce the computational complexity of those methods. Experimental results show that the proposed algorithm can significantly speed up the encoding process, especially for low bit-rate video sequences, without deteriorating the coding efficiency of SVC.

Efficient CABAC Rate Estimation for H.264/AVC Mode Decision

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In H.264/AVC coders, the optimal mode decision for each coding unit is achieved based on a calculation of the rate-distortion (R-D) cost for each candidate mode. In this letter, we propose a context-adaptive binary arithmetic coding (CABAC)-based rate estimation scheme that reduces the computational complexity of the R-D cost function evaluation. The complex and time-consuming calculation of the arithmetic coding is replaced by a table lookup based on the proposed CABAC rate model for fast rate estimation. The context modeling part of CABAC is also simplified to accelerate the rate estimation process. The experimental results show that the proposed estimator follows the actual rate with the coefficient of determination <formula formulatype="inline"><tex Notation="TeX">$R^2 = 0.9997$</tex></formula>. The proposed estimator yields about a 30% reduction in the computational complexity of the R-D optimized mode decision, thereby accelerating the entire encoder by about 17% to 25% with almost no degradation in the R-D performance. </para>