Joel Sole

Transform Coefficient Coding in HEVC

This paper describes transform coefficient coding in the draft international standard of High Efficiency Video Coding (HEVC) specification and the driving motivations behind its design. Transform coefficient coding in HEVC encompasses the scanning patterns and coding methods for the last significant coefficient, significance map, coefficient levels, and sign data. Special attention is paid to the new methods of last significant coefficient coding, multilevel significance maps, high-throughput binarization, and sign data hiding. Experimental results are provided to evaluate the performance of transform coefficient coding in HEVC.

Overview of the Range Extensions for the HEVC Standard: Tools, Profiles, and Performance

The Range Extensions (RExt) of the High Efficiency Video Coding (HEVC) standard have recently been approved by both ITU-T and ISO/IEC. This set of extensions targets video coding applications in areas including content acquisition, postproduction, contribution, distribution, archiving, medical imaging, still imaging, and screen content. In addition to the functionality of HEVC Version 1, RExt provide support for monochrome, 4:2:2, and 4:4:4 chroma sampling formats as well as increased sample bit depths beyond 10 bits per sample. This extended functionality includes new coding tools with a view to provide additional coding efficiency, greater flexibility, and throughput at high bit depths/rates. Improved lossless, near-lossless, and very high bit-rate coding is also a part of the RExt scope. This paper presents the technical aspects of HEVC RExt, including a discussion of RExt profiles, tools, applications, and provides experimental results for a performance comparison with previous relevant coding technology. When compared with the High 4:4:4 Predictive Profile of H.264/Advanced Video Coding (AVC), the corresponding HEVC 4:4:4 RExt profile provides up to ~25

Transform coefficient coding in HEVC

%, ~32%, and ~36% average bit-rate reduction at the same PSNR quality level for intra, random access, and low delay configurations, respectively.

Color palette for screen content coding

ITU-T VCEG and ISO/IEC MPEG have undertaken a joint standardization activity on video coding called High Efficiency Video Coding (HEVC). This paper describes the transform coefficient coding in the HEVC Test Model (WD5) and the motivations driving the design. The coefficient coding description encompasses the scan patterns and the coding methods of the last significant coefficient, significance map and coefficient level. Special focus is given to the method for coding the last significant coefficient in the block.

Adaptive Color-Space Transform for HEVC Screen Content Coding

With the prevalence of high speed Internet access, emerging video applications such as remote desktop sharing, virtual desktop infrastructure, and wireless display require high compression efficiency of screen contents. However, traditional intra and inter video coding tools were designed primarily for natural contents. Screen contents have significantly different characteristics compared with nature contents, e.g. sharp edges, less or no noise, which makes those traditional coding tools less sufficient. In this research, a new color palette based video coding tool is presented. Different from traditionally intra and inter prediction that mainly removes redundancy between different coding units, palette coding targets at the redundancy of repetitive pixel values/patterns within the coding unit. In the palette coding mode, a lookup table named palette which maps pixel values into table indices (also called palette indices) is signaled first. Then the mapped indice for a coding unit (which we call index block) are coded with a novel three-mode run-length entropy coding. Some encoder-side optimization for palette coding is also presented in detail in this paper. Simulation has been performed using the common screen content coding test condition defined by JCT-VC and the results show that palette coding can effectively improve screen content coding efficiency for both lossless and lossy scenarios.

Scalable Video Coding Extension for HEVC

This paper presents an in-loop adaptive color-space transform for the HEVC Screen Content Coding extension. In the proposed method, the prediction residual is adaptively converted into a different color space to reduce the cross-component redundancy. After the ACT, the signal is coded following the existing HEVC framework. To keep the complexity as low as possible, fixed color-space transforms that are easily implemented with shift and add operations are utilized. Significant coding gains are achieved by this method in the current HEVC Screen Content Coding reference software with no increase of decoding runtime. The proposed method has been adopted to the HEVC Screen Content Coding extension.

Palette Mode Coding in HEVC Screen Content Coding Extension

This paper describes a scalable video codec that was submitted as a response to the joint call for proposals issued by ISO/IEC MPEG and ITU-T VCEG on HEVC scalable extension. The proposed codec uses a multi-loop decoding structure. Several inter-layer texture prediction methods are employed to remove the inter-layer redundancy. Inter-layer prediction is also used when coding enhancement layer syntax elements such as motion parameter and intra prediction mode, to further reduce bit overhead. Additionally, alternative transforms as well as adaptive coefficients scanning are used to code the prediction residues more efficiently. Experimental results are presented to demonstrate the effectiveness of the proposed scheme. When compared to HEVC single-layer coding, the additional rate overhead for the proposed scalable extension is 1.2% to 6.4% to achieve two layers of SNR and spatial scalability.

Explicit residual DPCM for screen contents coding

Palette mode is a new coding tool included in the HEVC screen content coding extension (SCC) to improve the coding efficiency for screen contents such as computer generated video with substantial amount of text and graphics. It is observed that a local area in screen content typically has a few colors separated by sharp edges. To exploit such characteristics, palette mode represents samples in a block with indexes pointing to the color entries in a palette table. This paper provides a detailed overview of the palette mode in HEVC SCC in terms of palette generation, coding of the palette, and coding of the palette indexes for the samples in the palette block. Several improvements to palette mode coding, which have been proposed but not included in HEVC SCC, are also described. Simulation results are presented to quantify the bitrate savings provided by the palette mode for equal distortions.

Improved intra-block copy and motion search methods for screen content coding

In this paper, we propose an explicit signaling of RDPCM scheme for a lossy intra-coded block, and achieve a significant coding gain over the HEVC Range Extension reference software in the screen contents coding. We define three RDPCM modes, and transmit the side information so that the best RDPCM mode can be applied to residual signals after all available angular directional predictions. Contexts for a CABAC coding is also designed for coding the overheads.

Intra Block Copy for HEVC Screen Content Coding

Screen content video coding extension of HEVC (SCC) is being developed by Joint Collaborative Team on Video Coding (JCT-VC) of ISO/IEC MPEG and ITU-T VCEG. Screen content usually features a mix of camera captured content and a significant proportion of rendered graphics, text, or animation. These two types of content exhibit distinct characteristics requiring different compression scheme to achieve better coding efficiency. This paper presents an efficient block matching schemes for coding screen content to better capture the spatial and temporal characteristics. The proposed schemes are mainly categorized as a) hash based global region block matching for intra block copy b) selective search based local region block matching for inter frame prediction c) hash based global region block matching for inter frame prediction. In the first part, a hash-based full frame block matching algorithm is designed for intra block copy to handle the repeating patterns and large motions when the reference picture constituted already decoded samples of the current picture. In the second part, a selective local area block matching algorithm is designed for inter motion estimation to handle sharp edges, high spatial frequencies and non-monotonic error surface. In the third part, a hash based full frame block matching algorithm is designed for inter motion estimation to handle repeating patterns and large motions across the temporal reference picture. The proposed schemes are compared against HM-13.0+RExt-6.0, which is the state-of-art screen content coding. The first part provides a luma BD-rate gains of -26.6%, -15.6%, -11.4% for AI, RA and LD TGM configurations. The second part provides a luma BD-rate gains of -10.1%, -12.3% for RA and LD TGM configurations. The third part provides a luma BD-rate gains of -12.2%, -11.5% for RA and LD TGM configurations.