Kemal Ugur

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.

The emerging MVC standard for 3D video services

Multiview video has gained a wide interest recently. The huge amount of data needed to be processed by multiview applications is a heavy burden for both transmission and decoding. The joint video team has recently devoted part of its effort to extend the widely deployed H.264/AVC standard to handle multiview video coding (MVC). The MVC extension of H.264/AVC includes a number of new techniques for improved coding efficiency, reduced decoding complexity, and new functionalities for multiview operations. MVC takes advantage of some of the interfaces and transport mechanisms introduced for the scalable video coding (SVC) extension of H.264/AVC, but the system level integration of MVC is conceptually more challenging as the decoder output may contain more than one view and can consist of any combination of the views with any temporal level. The generation of all the output views also requires careful consideration and control of the available decoder resources. In this paper, multiview applications and solutions to support generic multiview as well as 3D services are introduced. The proposed solutions, which have been adopted to the draft MVC specification, cover a wide range of requirements for 3D video related to interface, transport of the MVC bitstreams, and MVC decoder resource management. The features that have been introduced in MVC to support these solutions include marking of reference pictures, supporting for efficient view switching, structuring of the bitstream, signalling of view scalability supplemental enhancement information (SEI) and parallel decoding SEI.

High Performance, Low Complexity Video Coding and the Emerging HEVC Standard

This paper describes a low complexity video codec with high coding efficiency. It was proposed to the high efficiency video coding (HEVC) standardization effort of moving picture experts group and video coding experts group, and has been partially adopted into the initial HEVC test model under consideration design. The proposal utilizes a quadtree-based coding structure with support for macroblocks of size 64 × 64, 32 × 32, and 16 × 16 pixels. Entropy coding is performed using a low complexity variable length coding scheme with improved context adaptation compared to the context adaptive variable length coding design in H.264/AVC. The proposals interpolation and deblocking filter designs improve coding efficiency, yet have low complexity. Finally, intra-picture coding methods have been improved to provide better subjective quality than H.264/AVC. The subjective quality of the proposed codec has been evaluated extensively within the HEVC project, with results indicating that similar visual quality to H.264/AVC High Profile anchors is achieved, measured by mean opinion score, using significantly fewer bits. Coding efficiency improvements are achieved with lower complexity than the H.264/AVC Baseline Profile, particularly suiting the proposal for high resolution, high quality applications in resource-constrained environments.

Block Merging for Quadtree-Based Partitioning in HEVC

The joint development of the upcoming High Efficiency Video Coding (HEVC) standard by ITU-T Video Coding Experts Group and ISO/IEC Moving Picture Experts Group marks a new step in video compression capability. In technical terms, HEVC is a hybrid video-coding approach using quadtree-based block partitioning together with motion-compensated prediction. Even though a high degree of adaptability is achieved by quadtree-based block partitioning, this approach has certain intrinsic drawbacks, which may result in redundant sets of motion parameters being transmitted. Previous work has shown that those redundancies can effectively be removed by merging the leafs of a particular quadtree structure. Following this concept, a block merging algorithm for HEVC is now proposed. This algorithm generates a single motion parameter set for a whole region of contiguous motion-compensated blocks. In this paper, we describe the various components of the proposed block merging algorithm and, using experimental evidence, demonstrate their benefits in terms of coding efficiency.

Special Section on the Joint Call for Proposals on High Efficiency Video Coding (HEVC) Standardization

The five papers in this special section were among those submitted in response to the joint call for proposals on high efficiency video coding (HEVC) standardization. Although at this point of development it is still unclear which specific elements the final HEVC standard will contain, the selection of the papers was made such that together they would cover most of the promising tools and technologies that seem likely to be included in the standard.

Angular intra prediction in High Efficiency Video Coding (HEVC)

New video coding solutions, such as the HEVC (High Efficiency Video Coding) standard being developed by JCT-VC (Joint Collaborative Team on Video Coding), are typically designed for high resolution video content. Increasing video resolution creates two basic requirements for practical video codecs; those need to be able to provide compression efficiency superior to prior video coding solutions and the computational requirements need to be aligned with the foreseeable hardware platforms. This paper proposes an intra prediction method which is designed to provide high compression efficiency and which can be implemented effectively in resource constrained environments making it applicable to wide range of use cases. When designing the method, special attention was given to the algorithmic definition of the prediction sample generation, in order to be able to utilize the same reconstruction process at different block sizes. The proposed method outperforms earlier variations of the same family of technologies significantly and consistently across different classes of video material, and has recently been adopted as the directional intra prediction method for the draft HEVC standard. Experimental results show that the proposed method outperforms the H.264/AVC intra prediction approach on average by 4.8 %. For sequences with dominant directional structures, the coding efficiency gains become more significant and exceed 10 %.

Motion Compensated Prediction and Interpolation Filter Design in H.265/HEVC

Coding efficiency gains in the new High Efficiency Video Coding (H.265/HEVC) video coding standard are achieved by improving many aspects of the traditional hybrid coding framework. Motion compensated prediction, and in particular the interpolation filter, is one area that was improved significantly over H.264/AVC. This paper presents the details of the interpolation filter design of the H.265/HEVC standard. First, the improvements of H.265/HEVC interpolation filtering over H.264/AVC are presented. These improvements include novel filter coefficient design with an increased number of taps and utilizing higher precision operations in interpolation filter computations. Then, the computational complexity is analyzed, both from theoretical and practical perspectives. Theoretical complexity analysis is done by studying the worst-case complexity analytically, whereas practical analysis is done by profiling an optimized decoder implementation. Coding efficiency improvements over the H.264/AVC interpolation filter are studied and experimental results are presented. They show a 4.0% average bitrate reduction for the luma component and 11.3% average bitrate reduction for the chroma components. The coding efficiency gains are significant for some video sequences and can reach up to 21.7%.

Video Coding With Low-Complexity Directional Adaptive Interpolation Filters

A novel adaptive interpolation filter structure for video coding with motion-compensated prediction is presented in this letter. The proposed scheme uses an independent directional adaptive interpolation filter for each sub-pixel location. The Wiener interpolation filter coefficients are computed analytically for each inter-coded frame at the encoder side and transmitted to the decoder. Experimental results show that the proposed method achieves up to 1.1 dB coding gain and a 15% average bit-rate reduction for high-resolution video materials compared to the standard nonadaptive interpolation scheme of H.264/AVC, while requiring 36% fewer arithmetic operations for interpolation. The proposed interpolation can be implemented in exactly 16-bit arithmetic, thus it can have important use-cases in mobile multimedia environments where the computational resources are severely constrained.

Error-tolerant interactive image segmentation using dynamic and iterated graph-cuts

Efficient and accurate interactive image segmentation have significant importance in many multimedia applications. For mobile touchscreen-based applications, efficiency is more crucial. Moreover, due to small screens of the mobile devices, error tolerance is also a crucial factor. In this paper, a method for interactive image segmentation, tailored for mobile touch screen devices, is proposed. As an interaction methodology, coloring is presented. An automatic stroke-error correction methodology to correct the inaccurate user interaction is also proposed. For the efficient computation of the solution, a novel dynamic and iterative graph-cut solution is formulated. Efficiency and error tolerance of the proposed method are tested by using various sample images. Subjective evaluation of the interactive segmentation algorithms for mobile-touch screen is also performed. Indeed, for the challenging examples, the superior performance of the proposed method is obtained by the experiments.

Low complexity video coding and the emerging HEVC standard

This paper describes a low complexity video codec with high coding efficiency. It was proposed to the High Efficiency Video Coding (HEVC) standardization effort of MPEG and VCEG, and has been partially adopted into the initial HEVC Test Model under Consideration design. The proposal utilizes a quad-tree structure with a support of large macroblocks of size 64×64 and 32×32, in addition to macroblocks of size 16×16. The entropy coding is done using a low complexity variable length coding based scheme with improved context adaptation over the H.264/AVC design. In addition, the proposal includes improved interpolation and deblocking filters, giving better coding efficiency while having low complexity. Finally, an improved intra coding method is presented. The subjective quality of the proposal is evaluated extensively and the results show that the proposed method achieves similar visual quality as H.264/AVC High Profile anchors with around 50% and 35% bit rate reduction for low delay and random-access experiments respectively at high definition sequences. This is achieved with less complexity than H.264/AVC Baseline Profile, making the proposal especially suitable for resource constrained environments.