Sang-hyo Park

Fast Intra Prediction Mode Decision based on Rough Mode Decision and Most Probable Mode in HEVC

High Efficiency Video Coding (HEVC), the latest video coding standard, has twice of the compression efficiency compared to AVC/H.264 under the same image quality condition. To obtain the improved efficiency, however, it was adopted for many methods which need complicated calculation, and the time complexity of HEVC was increased more than that of AVC/H.264. To solve this problem, the various fast algorithms have been researched. In this paper, we propose a fast intra prediction mode decision method which uses result of Rough Mode Decision (RMD) and Most Probable Mode (MPM). The proposed method selects a best predicted mode by comparing each predicted directions which are calculated through RMD and MPM. We applied the proposed method to HM 10.0 and conducted an comparing experiment in All-Intra environment. The experiment result showed that total encoding time is reduced by about 26% on average with about a 0.8% loss of BD-rate.

An Efficient Motion Estimation Method for QTBT Structure in JVET Future Video Coding

In this paper, an efficient motion estimation method for quadtree plus binary tree (QTBT) structure is presented for JVET future video coding (FVC). To exploit the possibility to design a new coding standard better than HEVC, an activity called future video coding has been active in MPEG and VCEG. One of the most influential new technologies proposed for FVC is QTBT structure, which can give more flexibility on the prediction block than quadtree-based HEVC. To advance the compression efficiency of QTBT, we propose a method that, for accurate motion estimation, sets a new point and adjusts search range accordingly based on the motion information of parent node. Performance evaluation was conducted on top of joint exploration model (JEM 3.0), which resulted in a 0.41% gain on average in terms of BD-rate under random access scenario without any burden on encoder complexity.

Efficient biprediction decision scheme for fast high efficiency video coding encoding

Abstract. An efficient biprediction decision scheme of high efficiency video coding (HEVC) is proposed for fast-encoding applications. For low-delay video applications, bidirectional prediction can be used to increase compression performance efficiently with previous reference frames. However, at the same time, the computational complexity of the HEVC encoder is significantly increased due to the additional biprediction search. Although a some research has attempted to reduce this complexity, whether the prediction is strongly related to both motion complexity and prediction modes in a coding unit has not yet been investigated. A method that avoids most compression-inefficient search points is proposed so that the computational complexity of the motion estimation process can be dramatically decreased. To determine if biprediction is critical, the proposed method exploits the stochastic correlation of the context of prediction units (PUs): the direction of a PU and the accuracy of a motion vector. Through experimental results, the proposed method showed that the time complexity of biprediction can be reduced to 30% on average, outperforming existing methods in view of encoding time, number of function calls, and memory access.

Objective and subjective evaluation of MPEG internet video coding

Internet video coding (IVC) is an exploration within MPEG to develop a video compression technology that is expected of royalty-free and targeted to the compression performance comparable to MPEG-4 AVC/H.264 Constrained Baseline Profile (CBP). IVC codec has been steadily enhanced since 2011, so it is valuable to report comparison results in the progress. In this paper, we evaluate the codec performance of IVC comparing with AVC CBP in terms of bitrate and PSNR together. Furthermore, we also evaluate the subjective quality of IVC with two types of viewers: MPEG experts and non-experts. The results show that the overall picture quality of IVC is comparable to AVC CBP except the subjective quality in low bitrate.

Efficient frame-by-frame QP assignment method for Internet video coding

In this paper, an efficient quantization parameter (QP) assignment method is proposed for MPEG internet video coding (IVC). QP is one critical control point in video compression performance. Instead of assigning the same QP value for each frame, the allocation of different QP values can increase the coding efficiency of standardized video codecs such as AVC/H.264 and HEVC along with the special group of structure (GOP) of those codecs. However, it has not been thoroughly investigated in general IPPP coding structure whether the QP variation is clearly effective or not. Thus, an efficient QP assignment method that assigns QP values frame-by-frame is proposed for the general IPPP coding structure. The proposed method exploits the advantages of hierarchical QP variation frame-by-frame. Extensive experiments were conducted to figure out how much QP variation improves coding performance upon internet video coding (IVC) encoder that has the general IPPP coding structure and is recently being developed by MPEG experts. As a result, the proposed method significantly increased the coding efficiency compared to the existing IVC test model 10.0, showing a 9.9% gain on average in terms of BD-rate.

Zero coefficient-aware fast butterfly-based inverse discrete cosine transform algorithm

The latest video coding standards, including Moving Picture Experts Group-4 (MPEG-4) advanced video coding (AVC)/H.264 and high-efficiency video coding (HEVC), use a discrete cosine transform (DCT) process as the core for compression efficiency, sacrificing the computational complexity at decoder. There have been a number of attempts to reduce the complexity of inverse DCT (IDCT). Butterfly-based factorisation remains the most commonly used method for such a reduction. In this study, the authors propose a zero (Z) coefficient-aware fast butterfly-based IDCT algorithm for video decoding. They focus on a reduction in the computational complexity of the butterfly-based 8 × 8 IDCT by removing the unnecessary computations of one-dimensional (1D) IDCT kernels, and adaptively applying IDCT kernels based on the number of non-Z DCT coefficients to speed-up 1D data. Their experimental results show that the average operation numbers using the proposed IDCT is approximately half that for the 8 × 8 IDCT implemented in the MPEG-4 AVC/H.264 and HEVC reference software. The improved computational complexity of the proposed method is demonstrated by measuring the running time, which requires only one-half of the IDCT time using the reference software.

Temporal correlation-based fast encoding algorithm in HEVC intra frame coding

In this paper, we propose a method that skips the complex encoding processes of coding unit (CU) for HEVC intra frame coding. To speed-up the encoding process that recursively explore all sizes of CUs, most researchers have exploited spatial information thus far. On the other hand, the temporal correlation among frames has not been thoroughly investigated. We exploited the temporal correlation as an early termination method, which skips ineffective unit sizes and associated cost. Simulation results are provided to verify the efficiency of the proposed method, showing a 32% time saving with a 0.2 % BD-rate loss on average compared to HEVC test model 10.0 under all-intra configuration.

An Efficient Parallelization Implementation of PU-level ME for Fast HEVC Encoding

In this paper, we propose an efficient parallelization technique of PU-level motion estimation (ME) in the next generation video coding standard, high efficiency video coding (HEVC) to reduce the time complexity of video encoding. It is difficult to encode video in real-time because ME has significant complexity (i.e., 80 percent at the encoder). In order to solve this problem, various techniques have been studied, and among them is the parallelization, which is carefully concerned in algorithm-level ME design. In this regard, merge estimation method using merge estimation region (MER) that enables ME to be designed in parallel has been proposed; but, parallel ME based on MER has still unconsidered problems to be implemented ideally in HEVC test model (HM). Therefore, we propose two strategies to implement stable parallel ME using MER in HM. Through experimental results, the excellence of our proposed methods is shown; the encoding time using the proposed method is reduced by 25.64 percent on average of that of HM which uses sequential ME.

CU depth-based ALF decision for fast HEVC encoding

In this paper, we propose a coding unit (CU) depth-based adaptive loop filter (ALF) decision method to reduce the encoder complexity. In high efficiency video coding (HEVC), ALF is designed based on Wiener filter to minimize the distortion between the original frame and the coded frame. In order to design the optimal filter for each CU, the filter design process is repeated 12 times per CU. The repetition of the filter design process occupies about 77 percent in the total ALF computation time, which substantially increases the encoder complexity. The proposed method simplifies the filter design with the CU depth-based ALF decision, which is based on the observation by exploiting ineffective computations. Experimental results show that the proposed method reduces the encoding time for the repetition of the filter design process by about 13 percent of that of the HEVC test model (i.e., HM 5.0) with 0.1 percent BD-rate increase.

Frame-based adaptive selection of ALF for fast HEVC decoding

Adaptive loop filter (ALF) is a newly introduced technique in high efficiency video coding (HEVC) that minimizes the distortion between the original frame and the coded frame. While ALF improves a coding efficiency as well as a visual quality in the video coding standard, the use of ALF increases the computational complexity at the decoder side substantially (e.g., 25 percent). This should be overcome for the implementation of fast decoder. In this paper, we propose an adaptive selection method that determines the use of ALF in a frame-level to reduce the decoding time. The proposed method exploits the fact that ALF is more effective in the frames with high RD cost values than in those with low RD cost values by determining the ALF-skip frame with the RD cost values of the current and previous frames. Through experimental results, the decoding time using the proposed method is reduced to about 93 percent of that of the HEVC test model (i.e. HM 3.0) with a 0.4 percent BD-rate increase.