Face-to-face bonded 3-D (F2F 3D) technology, with the potential to significantly reduce chip area while enhancing performance, stands as one of the most promising ways to extend Moore’s Law. However, current 3-D physical design flows are often modifications of 2-D design flows and rely on technical personnel to manually modify technical files. Furthermore, existing research on 3-D design flow primarily focuses on module implementation, with very few studies addressing hierarchical design methods for large-scale chips. In this article, we first introduce a 3-D physical design flow which concurrently optimizes the timing of both the logic tier and the memory tier, achieving synchronized physical design for both tiers. Then, we develop a bottom-up hierarchical 3-D physical design flow to extend the 3-D design flow to large-scale chip design. Through coordinated power planning, clock tree design, and interconnect unit design, we enhance the power, performance, and area (PPA) metrics of the entire chip. Using our RTL-to-GDS physical design flow, we successfully implemented a 28-nm CMOS logic-on-memory (LoM) 3-D coarse-grained reconfigurable architecture (CGRA) chip with over 50 million gates. Experimental results demonstrate that our 3-D flow improves timing by 16.1% while reducing voltage drop by 38.6% compared to the 2-D design. In addition, the power-delay product (PDP) of the 3-D chip decreases by 10.2%, showcasing better performance.

Motion compensated temporal filter (MCTF) is a pre-filtering technology for video encoding, which employs bilateral filtering to enhance temporal correlations among adjacent frames. In this paper, a spatial neighbor information assisted MCTF method is proposed, which introduces the spatial information into the motion estimation and bilateral filtering processes in MCTF to improve the coding efficiency. For the motion estimation process, the spatial neighbor information is involved in preventing motion estimation from capturing a local optimum. For the bilateral filtering process, the spatial neighbor information is employed as well to reduce the block boundary effect. The proposed method is implemented on top of the Fraunhofer Versatile Video Encoder (VVenC). Experimental results show that the proposed method can achieve 1.05% bitrate saving on average compared to the current MCTF scheme, and 10.33% bitrate saving compared with MCTF disabled.

The quad-tree plus binary-tree (QTBT) partition structures was adopted into the versatile video coding (VVC) standard. In the QTBT partition structure, a dual tree structure can be applied on intra slices where the partitioning structures for luminance and chrominance components are separate. The dual tree structure is efficient for camera captured videos. However, it may be not the case for screen content videos. Therefore, adaptive dual tree structure is proposed in this paper wherein the coding structure of each coding tree unit is switched between separate and joint coding structure to adapt the textures adaptively. The proposed scheme is implemented into the reference software of the VVC standard-VTM. Simulation results report that up to 4.5% BD bitrate saving can achieve on the typical screen content videos when compared to VTM5.

Palette mode is a powerful tool for screen content coding in the upcoming versatile video coding (VVC) standard. In the palette mode, escape samples are employed to handle an outlier case. In this paper, a quantization parameter (QP) dependent fixed-length binarization is proposed for escape samples coding to 1) simplify the design and 2) improve coding efficiency. The length is calculated according to the QP for the current block and correspondingly, the dequantization process can be also implemented by only left shifting. The proposed method is evaluated with VVC reference software VTM-6.0 on typical sequences containing "text and graphics with motion". Experimental results report that the proposed scheme can achieve up to 2.0% BD-rate savings compared to VTM-6.0 with a much simpler design.

The Joint Video Experts Team recently evaluated technology in response to a Call for Proposals for Video Compression with Capability beyond HEVC. A number of proposed solutions were evaluated, with a sub-set demonstrating the potential to reduce bit-rates by over 40% compared to HEVC. This paper presents the author's contributions to one of these proposals. The proposal emphasized a flexible, rectangular partitioning structure that was combined with new coding tools, including improved motion vector coding and quantization signaling methods. Results show the efficacy of the approach. Using the evaluation procedure defined in the Call, the described approach provides coding gains relative to an HEVC anchor of 41.2% and 35.7% for 4K-SDR and HD-SDR sequences, respectively, using the random access configuration; 29.0% for HD-SDR sequences using a low delay configuration, and gains of 34.3% and 32.2% for PQ-HDR and HLG-HDR sequences, respectively, using a random access configuration.

The Joint Video Exploration Team (JVET) has been developing an emerging standard Versatile Video Coding (VVC), which includes screen contents as one of its requirements. Intra block copy (IBC) and palette coding are the two powerful coding tools for screen content coding. In this paper, a compound palette mode is proposed to exploit the advantages of both IBC and palette coding, which allows samples to be reconstructed by either IBC predictions or palette entries. The proposed method is evaluated with VVC reference software VTM4 on typical sequences containing "text and graphics with motion". Experimental results report significant coding gain that the proposed scheme can achieve 7.80% and 1.03% BD-rate savings under AI conditions on average when compared with VTM4 and the existing palette scheme.

During the exploration of video coding technology for potential next generation standards, the Joint Video Exploration Team (JVET) has been studying quad-tree plus binary-tree (QTBT) partition structures within its Joint Exploration Model (JEM). This QTBT partition structure provides more flexibility compared with the quad-tree only partition structure in HEVC. Here, we further consider the QTBT structure and extended it to allow quad-tree partitioning to be performed both before and after a binary-tree partition. We refer to this structure as a compound split tree (CST). To show the efficacy of the approach, we implemented the method into JEM7. The method achieved 1.25%, 2.11% and 1.87% BD-bitrate savings for Y, U and V components on average under the random-access configuration, respectively.

Motion estimation plays an important role in video coding standards, such as H.264/AVC and HEVC. In this paper, we propose a multi-stage hash based motion estimation algorithm for HEVC, which enables hash based motion estimation for natural videos. In the proposed method, the prediction blocks significantly different from the current prediction unit will be eliminated in the motion estimation process. Locality sensitive hashing functions are used to measure the difference between the input block and predicted blocks. The proposed algorithm is implemented into the HM 12.0 software, and the simulation results show that the complexity of motion estimation is significantly reduced with negligible coding performance loss.

By considering the increasing importance of screen contents, the high efficiency video coding (HEVC) standard includes screen content coding as one of its requirements. In this paper, we demonstrate that enabling frame level block searching in HEVC can significantly improve coding efficiency on screen contents. We propose a hash-based block matching scheme for the intra block copy mode and the motion estimation process, which enables frame level block searching in HEVC without changing the HEVC syntaxes. In the proposed scheme, the blocks sharing the same hash values with the current block are selected as prediction candidates. Then the hash-based block selection is employed to select the best candidates. To achieve the best coding efficiency, the rate distortion optimization is further employed to improve the proposed scheme by balancing the coding cost of motion vectors and prediction difference. Compared with HEVC, the proposed scheme achieves 21% and 37% bitrate saving with all intra and low delay configurations with encoding time reduction. Up to 59% bitrate saving can be achieved on sequences with large motions.

Screen contents with complex structure contain random combination of texts, graphics and camera-captured images, which makes them difficult to be compressed efficiently by traditional video codecs. In this paper, we propose a 2-D dictionary based scheme to exploit the repeated patterns on screen content. In the proposed scheme, the current block is predicted from the reconstructed region using a hash-based block searching scheme. A hierarchical two-level hash based searching scheme is designed to find the best matching block for each block. The first-level hash function is used to search the blocks similar to the current block in the constructed 2-D dictionary. The second-level hash function is used to update the 2-D dictionary, which filters out the identical blocks from the blocks found using the first-level hash function. The proposed scheme is incorporated into HEVC framework as an additional mode. Experimental results show that the proposed scheme achieves significantly coding performance improvements on screen contents compared with HEVC.

Screen content like cartoons, captures of typical computer screens or video with text overlay or news ticker is an important category of video, which needs new techniques beyond the existing video coding techniques. In this paper, we analyze the characteristics of screen content and coding efficiency of HEVC on screen content. We propose a new coding scheme, which adopts a non-transform representation, separating screen content into color component and structure component. Based on the proposed representation, two coding modes are designed for screen content to exploit the directional correlation and non-translational changes in screen video sequences. The proposed scheme is then seamlessly incorporated into the HEVC structure and implemented into HEVC range extension reference software HM9.0. Experimental results show that the proposed scheme achieves up to 52.6% bitrate saving compared with HM9.0. On average, 35.1%, 29.2% and 23.6% bitrate saving are achieved with intra, random-access and low-delay configurations, respectively. The visual quality of the decoded video sequences is also significantly improved by reducing ringing artifacts around sharp edges and reserving the shape of text without blur.

Screen content refers to image/video generated by electronic devices. Existing state-of-art image/video coding standards don't exploit the anisotropic features. This paper proposes an adaptive LZMA-based coding scheme for screen content to achieve better coding efficiency. Adaptive scanning and directional matching are incorporated into LZMA in our scheme. Both of them exploit the directional correlations in screen content to increase the matching probability of LZMA, and thus achieve better coding performance. Experimental results show that the proposed scheme significantly outperforms existing LZMA-based coding schemes on screen content coding.

Computer generated compound images contain not only photographic images but also text and graphics images, which makes it difficult to be efficiently compressed using exiting image and video coding standards. This paper presents a new compound image coding scheme based on the intra coding framework of the upcoming high efficiency video coding (HEVC) standard. The proposed scheme first decomposes the compound image into color components and structure components. Then two-stage prediction scheme is employed to exploit the correlation among structure components, where the first prediction is generated by directional prediction and second prediction is generated by template matching. Experimental results show that the proposed scheme achieves up to 10.2 dB coding gain on compound images compared with HEVC. And on average it achieves 42.2 percent bitrate saving compared with HEVC.

H.264/AVC adopts intra coding technique to reduce spatial redundancies. In order to achieve better coding performance, there are nine candidate modes for 4×4 block unit to be selected by Rate-Distortion Optimization(RDO) process in the H.264/AVC encoder-side. However, too many intra candidate modes undoubtedly increase the transmitted bits that represent them. To solve this problem, a novel method for reducing the number of intra modes is proposed in this paper. For each 4×4 block, our algorithm can cluster the nine candidate modes into several groups and selects one mode from each group as a representative of all the modes in this group, so the cost of transmission can be reduced significantly because of the reduction of number of candidate modes. Experimental results show that the proposed method achieves 3.2% bit-rate reduction on average for various video sequences. The improvement of coding performance can be up to 7% bit-rate reduction at low bit rate, averagely.