Jongmin You

16x16 macroblock partition size prediction for H.264 P slices

H.264 uses variable block sizes for macroblock partition. The H.264 encoder allows 2 intra coding modes and 5 inter coding modes for a macroblock in a P slice. This is the most essential part for high compression efficiency but requires many computations to decide the most suitable coding mode. In this paper, we present a fast mode decision algorithm for H.264 P slices. To reduce complexity, we analyze the results of P16times16 ME (motion estimation) of a macroblock according to the proposed decision model, and if this macroblock is considered to be coded with a larger mode, we prevent motion estimations for smaller modes. From statistical analysis, we define a decision model which estimates whether the macroblock partition size is further divided or not. Our experimental results show that the proposed algorithm can achieve 11-63% computational savings without significant degradation of visual quality and increase in bit rate

Weighted Fuzzy Reasoning Scheme for Interlaced to Progressive Conversion

Video deinterlacing can be realized using time-space interpolation filters. To improve video deinterlacing quality with respect to missing pixels on moving diagonal lines, we developed a fuzzy concept that utilizes deinterlacing methods. The proposed algorithm consists of three parts. The first part is fuzzy rule-assisted edge-preserving-based deinterlacing (FED), which has an edge-preserving unit that utilizes fuzzy theory to find the most accurate edge direction and interpolates the missing pixels. Using the introduced gradients in the interpolation, the vertical resolution in the deinterlaced image is subjectively concealed. The second part is weighted fuzzy-reasoning-assisted deinterlacing (WFD), which works in the spatio-temporal domain. In this part, the computed weights are considered and multiplied by the candidate deinterlaced pixels, which successively build approximations of the deinterlaced sequence. The third part of the proposed algorithm is weighted fuzzy switching filtering, which analyzes the suitability of each method on system performance and uses a switching algorithm between FED and WFD. The outcome of image interpolation can be adjusted continuously by varying the setting of the membership function for fuzzy inference. Compared with conventional image interpolation methods, the algorithm presented in this paper provides improved edge quality in the deinterlaced image without the introduction of evident artifacts.

Complexity control strategy for real-time H.264/AVC encoder

The H.264/AVC encoder acquires high coding efficiency by using the various coding techniques, but requires very high computational complexity. Therefore, H.264/AVC encoder causes the problem of preserving acceptable video coding performance in the low-power/processor environments, such as wireless mobile. To optimize the rate-distortion (R-D) and complexity, we analyze the encoding structure and establish an analytic model for complexity. From this analysis, we propose a new approach for real-time encoder which maintains both frame rate and video quality. An encoding time control algorithm investigates the results of P16×16 motion estimation (ME) in the current frame and decides the number of skipped macro-blocks (MBs) in order to encode the frame within the allocated target encoding time. A complexity control algorithm manages the coding complexity of each frame by preventing motion estimations for smaller modes. Simulation results show that compared to the existing algorithm, the proposed algorithm can maintain frame rate without significant degradation of visual quality and increase in bit rate.

Contrast enhancement using histogram equalization based on logarithmic mapping

A widely used contrast enhancement method, the histogram equalization (HE) often produces images with unnatural appearances and visually disturbing artifacts because the HE compels the enhanced image to follow the uniform distribution. An adaptive histogram equalization using logarithmic mapping is presented, with a proposed algorithm based on a bin underflow and overflow method that achieves contrast enhancement by putting constraints on each histogram component differently. To incorporate characteristics of the human visual system, the logarithmic mapping function is used as constraint function, while the rate of contrast enhancement is controlled by determining the control parameters with the characteristics of the original image. The experimental results show that the proposed algorithm not only keeps the original histogram shape features, but also enhances the contrast effectively. Due to its simplicity, the proposed algorithm can be applied by simple hardware and processed in a real-time system.

Fast Mode Decision Algorithm Using Efficient Block Skip Techniques for H.264 P Slices

In this paper, we propose a fast algorithm that can reduce the complexity for inter mode decision of the H.264 encoder by minimizing a large number of calculations of inter mode decision process adaptively. The main idea is to use the technique skipping unnecessary macroblock modes. We focus on two block size modes, which is 16x16 and 8x8 block size modes, in proposed algorithm. The percentage of 16x16 block size modes is the largest in most of the sequences. This means that many redundant mode calculations can be removed. The percentage of 8x8 block size mode is small. But time consumption caused in the mode decision of encoder is very considerable. Therefore if we can extract the unnecessary 8x8 block size mode calculation well, a large amount of time can be saved in total encoding process. The experimental results show that the proposed algorithm can achieve up to 43% speed up ratio with a little PSNR loss. Increase of total bits encoded is also not much noticeable.

Modified rate distortion optimization using inter-block dependence for H.264/AVC intra coding

H.264/AVC allows several prediction schemes including variable modes for intra and inter predictions. To take full advantage of all allowed modes, H.264 employs rate distortion optimization (RDO) as its mode decision method. However, RDO incorporated into the H.264 encoder assumes block independence because calculating rate distortion (RD) cost for all possible mode sets requires a huge number of computations. In contrast to this assumption, coding efficiency of intra prediction in the H.264 encoder is affected by reference pixels in neighboring blocks. Thus, RDO in the H.264 encoder has potential to improve coding performance by considering the accuracy of intra prediction for the next blocks during the mode decision process of the current block. In this paper, we propose new criteria for I4 times 4 mode decision and by using this criteria, the proposed method considers more mode sets to improve RD performance compared to the original RDO. Although the proposed method requires more computations compared to the original RDO, experimental results indicate that the proposed method noticeably improves coding efficiency compared to the original RDO.

A Spatio-Temporal Fuzzy Interpolation Algorithm for Video Deinterlacing

This paper proposes a novel fuzzy reasoning interpolation method for video deinterlacing. We propose SMDW and TMDW parameters to measure the amount of entropy in the spatial and temporal domains. The shape of the membership function is designed adaptively according to the parameters, and can be utilized to determine edge direction. Our proposed fuzzy edge direction detector follows three processing steps: fuzzification, rule inference, and defuzzification. This filter operates by identifying small pixel variations in nine orientations (0 °, ±30 °, ±45 °, ±55 °, and ±60 °) in each domain, and works by using rules to infer the edge direction. Detection and interpolation results are presented. The results of computer simulations show that the proposed method is able to outperform a number of methods in the literature.

Adaptive Fast Inter Mode Decision Algorithm Using Dynamic Threshold Technique for H.264/AVC P Slices

H.264/AVC is adopted to a variety of applications because of its high compression efficiency. The high coding efficiency of H.264 is mainly acquired from the newly allowed prediction schemes including variable block mode. However these schemes require a high complexity to select the optimal mode. In this paper, to reduce this large computational burden, an adaptive fast inter mode decision algorithm using dynamic threshold technique for H.264/AVC P slices is proposed. In many sequences, the modes for large block such as SKIP and P16×16 occupy the most portions optimal modes. This fact gives us very important clue. The experimental results show that the proposed mode decision algorithm can reduce entire encoding time effectively by about 42.5% only without noticeable PSNR loss.

Probable mode prediction for H.264 advanced video coding P slices using removable SKIP mode distortion estimation

The H.264/AVC (advanced video coding) is used in a wide variety of applications including digital broadcasting and mobile applications, because of its high compression efficiency. The variable block mode scheme in H.264/AVC contributes much to its high compression efficiency but causes a selection problem. In general, rate-distortion optimization (RDO) is the optimal mode selection strategy, but it is computationally intensive. For this reason, the H.264/AVC encoder requires a fast mode selection algorithm for use in applications that require low-power and real-time processing. A probable mode prediction algorithm for the H.264/AVC encoder is proposed. To reduce the computational complexity of RDO, the proposed method selects probable modes among all allowed block modes using removable SKIP mode distortion estimation. Removable SKIP mode distortion is used to estimate whether or not a further divided block mode is appropriate for a macroblock. It is calculated using a no-motion reference block with a few computations. Then the proposed method reduces complexity by performing the RDO process only for probable modes. Experimental results show that the proposed algorithm can reduce encoding time by an average of 55.22% without significant visual quality degradation and increased bit rate.

Fuzzy Rule Based Edge-Sensitive Line Average Algorithm in Interlaced HDTV Sequences

This paper proposes a spatial domain deinterlacing method which is based on fuzzy rule and edge-sensitive line average algorithm. The proposed algorithm consists two parts: edge direction detection part and fuzzy rule based edge-sensitive interpolation part. Once the edge direction is determined, in order to accurately reconstruct boundary of edges and peaks, edge-sensitive interpolation is utilized. Detection and interpolation results are presented. Experimental results show that the proposed algorithm provides a significant improvement over other existing deinterlacing methods.