Jung-Hye Min

Intra Coding of the HEVC Standard

This paper provides an overview of the intra coding techniques in the High Efficiency Video Coding (HEVC) standard being developed by the Joint Collaborative Team on Video Coding (JCT-VC). The intra coding framework of HEVC follows that of traditional hybrid codecs and is built on spatial sample prediction followed by transform coding and postprocessing steps. Novel features contributing to the increased compression efficiency include a quadtree-based variable block size coding structure, block-size agnostic angular and planar prediction, adaptive pre- and postfiltering, and prediction direction-based transform coefficient scanning. This paper discusses the design principles applied during the development of the new intra coding methods and analyzes the compression performance of the individual tools. Computational complexity of the introduced intra prediction algorithms is analyzed both by deriving operational cycle counts and benchmarking an optimized implementation. Using objective metrics, the bitrate reduction provided by the HEVC intra coding over the H.264/advanced video coding reference is reported to be 22% on average and up to 36%. Significant subjective picture quality improvements are also reported when comparing the resulting pictures at fixed bitrate.

Block Partitioning Structure in the HEVC Standard

High Efficiency Video Coding (HEVC) is the latest joint standardization effort of ITU-T WP 3/16 and ISO/IEC JTC 1/SC 29/WG 11. The resultant standard will be published as twin text by ITU-T and ISO/IEC; in the latter case, it will also be known as MPEG-H Part 2. This paper describes the block partitioning structure of the draft HEVC standard and presents the results of an analysis of coding efficiency and complexity. Of the many new technical aspects of HEVC, the block partitioning structure has been identified as representing one of the most significant changes relative to previous video coding standards. In contrast to the fixed size 16 × 16 macroblock structure of H.264/AVC, HEVC defines three different units according to their functionalities. The coding unit defines a region sharing the same prediction mode, e.g., intra and inter, and it is represented by the leaf node of a quadtree structure. The prediction unit defines a region sharing the same prediction information. The transform unit, specified by another quadtree, defines a region sharing the same transformation. This paper introduces technical details of the block partitioning structure of HEVC with an emphasis on the method of designing a consistent framework by combining the three different units together. Experimental results are provided to justify the role of each component of the block partitioning structure and a comparison with the H.264/AVC design is performed.

Improved Video Compression Efficiency Through Flexible Unit Representation and Corresponding Extension of Coding Tools

This paper proposes a novel video compression scheme based on a highly flexible hierarchy of unit representation which includes three block concepts: coding unit (CU), prediction unit (PU), and transform unit (TU). This separation of the block structure into three different concepts allows each to be optimized according to its role; the CU is a macroblock-like unit which supports region splitting in a manner similar to a conventional quadtree, the PU supports nonsquare motion partition shapes for motion compensation, while the TU allows the transform size to be defined independently from the PU. Several other coding tools are extended to arbitrary unit size to maintain consistency with the proposed design, e.g., transform size is extended up to 64 × 64 and intraprediction is designed to support an arbitrary number of angles for variable block sizes. Other novel techniques such as a new noncascading interpolation Alter design allowing arbitrary motion accuracy and a leaky prediction technique using both open-loop and closed-loop predictors are also introduced. The video codec described in this paper was a candidate in the competitive phase of the high-efficiency video coding (HEVC) standardization work. Compared to H.264/AVC, it demonstrated bit rate reductions of around 40% based on objective measures and around 60% based on subjective testing with 1080 p sequences. It has been partially adopted into the first standardization model of the collaborative phase of the HEVC effort.

Extraction and temporal segmentation of multiple motion trajectories in human motion

A new method for extraction and temporal segmentation of multiple motion trajectories in human motion is presented. The proposed method extracts motion trajectories generated by body parts without any initialization or any assumption on color distribution. Motion trajectories are very compact and representative features for activity recognition. Tracking human body parts (hands and feet) is inherently difficult because the body parts which generate most of the motion trajectories are relatively small compared to the human body. This problem is overcome by using a new motion segmentation method: at every frame, candidate motion locations are detected and set as significant motion points (SMPs). The motion trajectories are obtained by combining these SMPs and the color-optical flow based tracker results. These motion trajectories are inturn used as features for temporal segmentation of specific activities from continuous video sequences. The proposed approach is tested on actual ballet step sequences. Experimental results show that the proposed method can successfully extract and temporally segment multiple motion trajectories from human motion.

49.1: New Concept for Improvement of White Color Balance in Hologram Back-light Units

We have improved a white color balance using multi-grating period structure in the holographic backlight units that can be applicable to mobile LCD panel where several LEDs are placed at edge of guide plate as light sources. New H-LGP is based on the characteristics of grating and its diffraction angle can be determined by specific grating period. With this idea, hologram backlight unit can realize not only lower weight and less power consumption but also higher light utilization by eliminating couple of prismatic sheets which have been widely used in conventional unit inevitably.

Holographic backlight unit for mobile LCD devices

— The commercial backlight unit for a portable liquid-crystal display (LCD) device typically consists of several light-emitting diodes (LEDs) as the light source, a couple of prismatic sheets and diffusers, and a guide plate for backlight optics. A simplified backlight unit for portable LCDs, merely consisting of a hologram-imprinted light-guide plate (H-LGP) and one diffuser, is proposed in this paper. By employing H-LGP, it is expected that several optical films essential to the conventional backlight unit can be eliminated. This paper aims to improve the optical efficiency of LGPs by deriving the design parameters of the H-LGP and performing the related computations. The angular luminance distribution of the emanating light from H-LGP has been measured and compared with the results obtained by simulation. A proper collimation is necessary in order to increase the luminance. The backlight developed through this work has high optical performance combined with low cost.

Coding efficiency improvements beyond HEVC with known tools

In this paper, several coding tools are evaluated on top of the HEVC version 1. Among them there are straightforward extension of HEVC coding tools (such as Coding Unit size enlarging, fine granularity of Intra prediction angles) and algorithms that have been studied during HEVC development (such as secondary transform, multi-hypothesis CABAC, multi-parameter Intra prediction, bidirectional optical flow). Most of them improve performance of Intra coding. Minor adjustment to the final version of HEVC standard was done for efficient harmonization of the proposed coding tools with HEVC. Performance improvement observed from investigated tools is up to 7,1%, 9,9%, 4,5% and 5,7% in all-intra, random access, low-delay B and low-delay P test scenario (using HEVC common test conditions).

Inter-layer intra mode prediction for scalable extension of HEVC

This paper introduces a novel inter-layer intra mode prediction method for scalable extension of High Efficiency Video Coding (HEVC) standard, which is being developed by the Joint Collaborative Team on Video Coding (JCT-VC). In HEVC and its scalable extension, thirty-five intra prediction modes are adopted to reduce the spatial redundancy of luma texture within one frame, which may introduce noticeable overhead of delivering the intra mode information in the scalable bit-stream. In this paper, the correlation of intra modes between different layers is exploited to improve the efficiency of intra mode coding in enhancement layer. The intra modes in enhancement layer are mainly predicted with the ones of collocated blocks at base layer. Two techniques are presented in this paper with some differences in terms of the derivation of intra mode predictor from base layer and the selection of three most probable modes at enhancement layer. Compared to Test Model version 1.0 of HEVC scalable extension, 0.4% and 0.1% bit-rate reductions can be achieved with technique 2 in All Intra 2x spatial scalability and All Intra 1.5x spatial scalability respectively, while technique 1 can achieve 0.2% and 0.1% reductions. There is no obvious running time increase for both encoder and decoder.

Large and various shapes block processing in HEVC

Recently, Joint Collaborative Team on Video Coding (JCT-VC) which is joint team by ITU-T SG 16 Q.6 (VCEG) and ISO/IEC JTC1/SC29/WG11 (MPEG) was established and started to define new video coding standard called as High Efficiency Video Coding (HEVC). This paper introduces block partitioning structure of HEVC standard and presents its analysis results. Among many technical aspects of HEVC, the block partitioning structure has been considered as a key factor of its significant coding efficiency improvement. Compared with the macroblock structure of the fixed size 16x16 in H.264/AVC, HEVC defines three flexible size units according to their functionalities. Coding unit (CU) defines a region sharing the same prediction scheme between spatial and temporal predictions and it is represented by the leaf node of the quadtree structure. Moreover, prediction unit (PU) defines a region sharing the same prediction information and transform unit (TU), which is specified by another quadtree, defines a region sharing the same transformation. This paper introduces technical details of the block partitioning structure of HEVC with emphasis on the consistently designed framework by combining three different units together. Provided experimental results justifies each component of the block partitioning structure.