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IEEE International Symposium on Circuits and Systems (ISCAS)

作者： Wenyi Wang Yingzhan Xu Bharath Vishwanath Kai Zhang Li Zhang Multimedia Lab Bytedance Inc.

ISBN: (数字)9798350330991

ISBN: (纸本)9798350331004

Point cloud compression has emerged as a hot research topic in recent years. Due to applications such as autonomous driving, LiDAR point cloud compression is an important research aspect of this field. Moving Picture Experts Group (MPEG) is developing a standard called Geometry-based Point Cloud Compression (G-PCC) to meet the compression requirements of point clouds from different collection devices including LiDAR. In current G-PCC, the prior information of spinning LiDAR is not fully utilized in octree geometry coding. In this paper, we address this issue and effectively account for the prior information of spinning LiDAR to improve the compression efficiency of octree geometry coding. Specifically, the angle information provided by capture laser scanner is utilized for Inferred Direct coding Mode (IDCM) eligibility criterion and z coordinate compensation of the reconstructed point cloud. Experimental results demonstrate that the proposed method achieves 6.7% and 16.4% average coding gain under D1 and D2 quality metrics, respectively, with a negligible increase in complexity. The major part of the proposed method has been adopted in G-PCC.

关键词： Point cloud compression Geometry Measurement Laser radar Octrees transform coding Encoding

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transform coding IN AVS2

TRANSFORM CODING IN AVS2

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IEEE International Conference on Multimedia and Expo Workshops

作者： Silong Wang Xingguo Zhu Dandan Ding Lu Yu Institute of Information and Communication Engineering Zhejiang University Zhejiang Provincial Key Laboratory of Information Network Technology

ISBN: (纸本)9781479947164

This paper describes the transform coding in the second generation of Audio-video coding Standard (AVS2). In AVS2, 16-bit integer DCT transform scheme is adopted, with the transform block size varies from 4×4 to 32×32, and the smaller transform kernels are completely embedded in the larger ones. To keep strong decorrelation capability of the transform, a principle is proposed in this paper to design the transform kernel by jointly minimizing DCT distortion, orthogonality and normalization. Furthermore, complexity of the transform is analyzed based on the proposed hybrid butterfly architecture, in which the transform is decomposed into a butterfly structure and a low-cost matrix multiplication. Experiment result shows that 25.7% additions and 71.0% shift operations can be saved by using this architecture compared with the partial butterfly one.

关键词： AVS2 DCT transform coding Architecture

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The JPEG Pleno Light Field coding Standard 4D-transform Mode: How to Design an Efficient 4D-Native Codec

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IEEE ACCESS 2020年 8卷 170807-170829页

作者： De Oliveira Alves, Gustavo De Carvalho, Murilo Bresciani Pagliari, Carla L. Freitas, Pedro Garcia Seidel, Ismael Pereira, Marcio Pinto Vieira, Carla Florentino Schueler Testoni, Vanessa Pereira, Fernando Da Silva, Eduardo A. B. Univ Fed Rio de Janeiro POLI DEL PEECOPPE BR-21941901 Rio de Janeiro Brazil Univ Fed Fluminense CTC TET BR-24220900 Niteroi RJ Brazil IME PGED PEE BR-22290270 Rio De Janeiro Brazil Samsung R&D Inst Brazil SRBR BR-13084791 Campinas Brazil Univ Lisbon Inst Telecomunicacoes Inst Super Tecn P-1049001 Lisbon Portugal

The increasing demand for highly realistic and immersive visual experiences has led to the emergence of richer 3D visual representation models such as light fields, point clouds and meshes. Light fields may be modelled as a 2D array of 2D views, corresponding to a large amount of data, which demands for highly efficient coding solutions. Although static light fields are inherently 4D structures, the coding solutions in the literature mostly employ traditional 2D coding tools associated with techniques such as depth-based image rendering to generate a residual, again to be coded using available 2D coding tools. To address the market needs, JPEG has launched the so-called JPEG Pleno standard, which Part 2 is dedicated to light field coding. The JPEG Pleno Light Field coding standard includes two coding modes, one based on the 4D-DCT, so-called 4D-transform mode, and another based on depth-based synthesis, so-called 4D-Prediction. The 4D-transform coding mode standardizes for the first time a 4D-native light field coding solution where the full light field redundancy across the four dimensions is comprehensively exploited, somehow extending to 4D the 2D coding framework adopted decades ago by the popular JPEG Baseline standard. In this context, this paper describes and analyzes in detail the conceptual and algorithmic design process which has led to the creation of the JPEG Pleno Light Field coding standard 4D-transform coding mode. This has happened through a sequence of steps involving technical innovation design and integration where increasingly sophisticated coding tools have been combined and improved to maximize the final rate distortion (RD) performance.

关键词： Encoding transform coding Standards Two dimensional displays Three-dimensional displays Visualization JPEG Pleno standard light field coding 4D-transform mode 4D-DCT

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transform coding of Self-Similar Processes based on the Wigner-Ville Distribution for Inference on Vehicular Accelerometer Data

Transform Coding of Self-Similar Processes based on the Wign...

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Data Compression Conference (DCC)

作者： Rahul Sinha Balamurali. P. Tapas Chakravarty Tata Consultancy Services Innovation Labs Bangalore

ISBN: (纸本)9781479934188

Accelerometer data collected from moving vehicles can be modeled as a self-similar random process. A Renyi entropy measure computed over the Wigner-Ville distribution of this non-stationary process is used to select the most relevant data samples for compression. Wavelet transform based transform coding is applied to compress the accelerometer data with minimal distortion and accurate inferences (detection of events) on the reconstructed data using the Cher off distance.

关键词： Entropy Time-frequency analysis Accelerometers Wavelet transforms transform coding Random processes

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On Aliased Resizing and Surprising Subtleties in GAN Evaluation

On Aliased Resizing and Surprising Subtleties in GAN Evaluat...

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IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR)

作者： Parmar, Gaurav Zhang, Richard Zhu, Jun-Yan Carnegie Mellon Univ Pittsburgh PA 15213 USA Adobe Res San Francisco CA USA

ISBN: (数字)9781665469463

ISBN: (纸本)9781665469463

Metrics for evaluating generative models aim to measure the discrepancy between real and generated images. The often-used Frechet Inception Distance (FID) metric, for example, extracts "high-level" features using a deep network from the two sets. However, we find that the differences in "low-level" preprocessing, specifically image resizing and compression, can induce large variations and have unforeseen consequences. For instance, when resizing an image, e.g., with a bilinear or bicubic kernel, signal processing principles mandate adjusting prefilter width depending on the downsampling factor, to antialias to the appropriate bandwidth. However, commonly-used implementations use a fixed-width prefilter, resulting in aliasing artifacts. Such aliasing leads to corruptions in the feature extraction downstream. Next, lossy compression, such as JPEG, is commonly used to reduce the file size of an image. Although designed to minimally degrade the perceptual quality of an image, the operation also produces variations downstream. Furthermore, we show that if compression is used on real training images, FID can actually improve if the generated images are also subsequently compressed. This paper shows that choices in low-level image processing have been an under-appreciated aspect of generative modeling. We identify and characterize variations in generative modeling development pipelines, provide recommendations based on signal processing principles, and release a reference implementation to facilitate future comparisons.

关键词： Measurement Training Image coding Computational modeling Pipelines transform coding Signal processing

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Dual Link Image coding Based on CCSDS-123

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IEEE GEOSCIENCE AND REMOTE SENSING LETTERS 2022年 19卷 1页

作者： Bartrina-Rapesta, Joan Auli-Llinas, Francesc Univ Autonoma Barcelona Dept Informat & Commun Engn E-08193 Bellaterra Spain

Predictive coding techniques are attractive for image codecs because they can yield high compression efficiency while spending few computational resources. In remote sensing, predictive techniques are employed in prominent standards to transmit images captured by Earth Observation (EO) satellites. Although EO satellites have full duplex capacity, compression standards for spatial data are devised to use the downlink only. Recently, we presented a dual-link image coding system that employs both the uplink and the downlink to accelerate the transmission of such images. The proposed system was introduced in the wavelet-based JPEG2000 standard, which is not well-suited for satellites due to its complexity. This letter approaches the dual-link scheme to a more suitable standard for spatial data based on predictive coding, more precisely, the Lossless Multispectral and Hyperspectral image compression standard CCSDS-123.0-B.2. The proposed method adapts the dual-link image coding scheme to CCSDS-123.0-B-2 by incorporating a quantizer, a lightweight arithmetic coder, and a rate control technique. Experimental results suggest that the resulting system achieves higher coding ratios than CCSDS-123.0-B-2 and JPEG2000 with dual link.

关键词： Image coding Satellites Entropy Encoding transform coding Standards Redundancy CCSDS-123 0-B-2 dual link image coding remote sensing images

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Performance Evaluation of Objective Quality Assessment Methods for Omnidirectional Images Under Emerging Compressions

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IEEE ACCESS 2024年 12卷 150419-150429页

作者： Simka, Marek Polak, Ladislav Novotny, Martin Kufa, Jan Fliegel, Karel Brno Univ Technol Fac Elect Engn & Commun Dept Radioelect Brno 61600 Czech Republic Czech Tech Univ Fac Elect Engn Dept Radioelect Prague 16627 Czech Republic

This paper presents a unique study of objective and subjective image quality assessment (IQA) of 360 degrees images, distorted by emerging and legacy compressions - AV1 Image File Format (AVIF), Joint Photographic Experts Group (JPEG), High Efficiency Image File Format (HEIC), JPEG XL from the cross-lab experiments carried out by two universities. The performance evaluation of objective conventional IQA methods relied on statistical data analysis employing not only traditional approaches with correlation coefficients but also advanced techniques such as Receiver Operating Characteristic (ROC) analysis, which offers several statistical advantages. The comprehensive statistical examination presented, utilizing an outcome from the subjective experiment with 66 observers, confirmed that the performance of specific IQA metrics depends not only on the image features but also on the applied image compression algorithm. Overall, the study examined nine IQA objective metrics. For instance, when evaluating distortion caused by the AVIF and HEIC codecs, the Multi-Scale Structural Similarity (MS-SSIM) metric exhibited the best performance, while the Feature Similarity chrominance (FSIMc) metric excelled in assessing JPEG-based compressions. Additionally, detailed outcomes of the subjective experiments, including eye-tracking data, are available in a public dataset. This study provides previously unexplored insights into the performance of conventional objective metrics for 360 degrees images degraded by emerging image codecs. The presented results suggest suitable metrics for specific application scenarios (codecs) and, along with the dataset, lay the groundwork for further research on new objective quality assessment methods for omnidirectional images under emerging compressions.

关键词： Image coding Measurement Visualization Quality assessment Codecs transform coding Image quality Observers Image color analysis Distortion Omnidirectional image (360 degrees) 360-degree content virtual reality objective quality assessment subjective test perceptual image quality

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High-Bit-Depth Geometry Representation and Compression in MPEG Immersive Video System

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IEEE ACCESS 2024年 12卷 189064-189072页

作者： Lee, Yoonseob Oh, Kwan-Jung Lee, Gwangsoon Oh, Byung Tae Korea Aerosp Univ Dept Elect & Informat Engn Goyang 10540 South Korea Elect & Telecommun Res Inst ETRI Immers Media Res Sect Daejeon 34129 South Korea Korea Aerosp Univ Dept Comp Engn Goyang 10540 South Korea

Immersive video has been rapidly evolving as a new form of media for virtual reality (VR) applications, increasing demand for efficient compression and transmission techniques. As immersive videos comprise multiple two-dimensional videos, compressing these videos individually incurs a high computational cost. MPEG has been standardizing immersive video coding, referred to as MPEG Immersive Video (MIV), wherein the redundant parts of immersive videos between views are pruned and combined into atlas videos, which are then coded using a conventional video codec. However, the original high-bit-depth geometry information is quantized to fit the conventional video codec during this process, leading to the loss of detailed sub-bit information. This paper presents a novel high-bit-depth geometry representation method, wherein the remaining bits after quantization are assigned to the chrominance channel to improve the performance of rendering the videos. Additionally, adequate preprocessing is proposed for bit assignment in the YUV 4:2:0 format. The performed experiments indicate that the proposed method reduces the BD-rate by approximately 7% on average by improving the rendering performance without modifying the existing MIV system.

关键词： Geometry Rendering (computer graphics) Video codecs transform coding Quantization (signal) Media Image color analysis Computational efficiency Standards Image coding High-bit-depth representation geometry representation immersive video depth colorization

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Efficient and Effective Blind JPEG Image Improvement With Sequential Feature Processing

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IEEE ACCESS 2024年 12卷 151975-151986页

作者： Ezumi, Shinya Ikehara, Masaaki Keio Univ Dept Elect & Elect Engn Yokohama 2238522 Japan

Image compression technologies such as JPEG enable efficient use of digital images. However, these technologies also degrade the quality of the image, resulting in a poor visual appearance and reduced usability. One way to solve the quality problem and achieve high efficiency in using high-quality JPEG images is to use quality improvement technologies based on artifact removal. In recent years, various methods using machine-learning-optimized neural networks have been devised to achieve high performance whereas maintaining versatility for JPEG images with various qualities. On the other hand, methods that achieve high-quality images need enormous computing costs, which is a barrier to easy use, especially when using images with large size. Given this situation, this paper proposes a method that achieves higher performance with smaller computational resources while maintaining the image quality in broader situations. The proposed method consists of a Quality Estimation Part (QE Part) that estimates the quality of the input image and Image Processing Parts (IP Parts) that process the image based on the estimated quality representation. Sequential processing is carried out by connecting multiple IP Parts in a cascade, which enables efficient and effective processing of different features. Each IP Part consists of multiple Processing Blocks, which enable effective quality improvement while maintaining efficiency. These measures enable the proposed method to achieve state-of-the-art quantitative results and better qualitative results that outperform conventional methods for images with various qualities. The code and the pre-trained models are released at https://***/ezumi-keio/Sequential_Processing-main.

关键词： transform coding Image coding IP networks Estimation Costs Noise measurement Image quality Usability Convolutional neural networks Computational efficiency Deep learning Image processing Sequential analysis double compressed image image processing JPEG JPEG image improvement JPEG artifact removal sequential processing

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Hardware architecture optimization for high-frequency zeroing and LFNST in H.266/VVC based on FPGA

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JOURNAL OF REAL-TIME IMAGE PROCESSING 2024年第3期21卷 90-90页

作者： Zhang, Junxiang Sheng, Qinghua Pan, Rui Wang, Jiawei Qin, Kuan Huang, Xiaofang Niu, Xiaoyan Hangzhou Dianzi Univ Sch Elect & Informat Hangzhou 310018 Peoples R China Dianzi Univ Sch Elect Engn Informat Engn Coll Hangzhou 311305 Peoples R China

To reduce the hardware implementation resource consumption of the two-dimensional transform component in H.266 VVC, a unified hardware structure is proposed that supports full-size Discrete Cosine transform (DCT), Discrete Sine transform (DST), and full-size Low-Frequency Non-Separable transform (LFNST). This paper presents an area-efficient hardware architecture for two-dimensional transforms based on a general Regular Multiplier (RM) and a high-throughput hardware design for LFNST in the context of H.266/VVC. The first approach utilizes the high-frequency zeroing characteristics of VVC and the symmetric properties of the DCT-II matrix, allowing the RM-based architecture to use only 256 general multipliers in a fully pipelined structure with a parallelism of 16. The second approach optimizes the transpose operation of the input matrix for LFNST in a parallelism of 16 architecture, aiming to save storage and logic resources.

关键词： H.266/VVC transform coding Hardware architecture LFNST High-frequency zeroing

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