Fast algorithm for the 3-D DCT-II

Recently, many applications for three-dimensional (3-D) image and video compression have been proposed using 3-D discrete cosine transforms (3-D DCTs). Among different types of DCTs, the type-II DCT (DCT-II) is the most used. In order to use the 3-D DCTs in practical applications, fast 3-D algorithms are essential. Therefore, in this paper, the 3-D vector-radix decimation-in-frequency (3-D VR DIF) algorithm that calculates the 3-D DCT-II directly is introduced. The mathematical analysis and the implementation of the developed algorithm are presented, showing that this algorithm possesses a regular structure, can be implemented in-place for efficient use of memory, and is faster than the conventional row-column-frame (RCF) approach. Furthermore, an application of 3-D video compression-based 3-D DCT-II is implemented using the 3-D new algorithm. This has led to a substantial speed improvement for 3-D DCT-II-based compression systems and proved the validity of the developed algorithm

Compression domain volume rendering for distributed environments

This paper describes a method for volume data compression and rendering which bases on wavelet splats. The underlying concept is especially designed for distributed and networked applications, where we assume a remote server to maintain large scale volume data sets, being inspected, browsed through and rendered interactively by a local client. Therefore, we encode the server‘s volume data using a newly designed wavelet based volume compression method. A local client can render the volumes immediately from the compression domain by using wavelet footprints, a method proposed earlier. In addition, our setup features full progression, where the rendered image is refined progressively as data comes in. Furthermore, framerate constraints are considered by controlling the quality of the image both locally and globally depending on the current network bandwidth or computational capabilities of the client. As a very important aspect of our setup, the client does not need to provide storage for the volume data and can be implemented in terms of a network application. The underlying framework enables to exploit all advantageous properties of the wavelet transform and forms a basis for both sophisticated lossy compression and rendering. Although coming along with simple illumination and constant exponential decay, the rendering method is especially suited for fast interactive inspection of large data sets and can be supported easily by graphics hardware

JSCC-Cast: A Joint Source Channel Coding Video Encoding and Transmission System with Limited Digital Metadata

[Abstract] This work considers the design and practical implementation of JSCC-Cast, a comprehensive analog video encoding and transmission system requiring a reduced amount of digital metadata. Suitable applications for JSCC-Cast are multicast transmissions over time-varying channels and Internet of Things wireless connectivity of end devices having severe constraints on their computational capabilities. The proposed system exhibits a similar image quality compared to existing analog and hybrid encoding alternatives such as Softcast. Its design is based on the use of linear transforms that exploit the spatial and temporal redundancy and the analog encoding of the transformed coefficients with different protection levels depending on their relevance. JSCC-Cast is compared to Softcast, which is considered the benchmark for analog and hybrid video coding, and with an all-digital H.265-based encoder. The results show that, depending on the scenario and considering image quality metrics such as the structural similarity index measure, the peak signal-to-noise ratio, and the perceived quality of the video, JSCC-Cast exhibits a performance close to that of Softcast but with less metadata and not requiring a feedback channel in order to track channel variations. Moreover, in some circumstances, the JSCC-Cast obtains a perceived quality for the frames comparable to those displayed by the digital one.This work has been funded by the Xunta de Galicia (by grant ED431C 2020/15 and grant ED431G 2019/01 to support the Centro de Investigación de Galicia “CITIC”), the Agencia Estatal de Investigación of Spain (by grants RED2018-102668-T and PID2019-104958RB-C42), and ERDF funds of the EU (FEDER Galicia 2014–2020 and AEI/FEDER Programs, UE)Xunta de Galicia; ED431C 2020/15Xunta de Galicia; ED431G 2019/0

Feature-preserving Reduction and Visualization of Industrial CT data using GLCM texture analysis and Mass-spring Model Deformation

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2014. 8. 신영길.본 논문에서는 3D 볼륨 데이터에서 중요한 영역을 보존하면서 크기를 줄이는 방법을 제안한다. 볼륨 데이터에서 어느 부분이 중요한 영역인지를 결정하기 위해 질감 분석 방법 중 하나인 GLCM 균일도를 이용한 중요도 측정 모델을 제안하고, 이를 기반으로 한 MSM 기반의 볼륨 변형을 수행한다. 중요도가 반영된 볼륨 변형 과정을 통해, 중요한 영역은 상대적으로 크기가 확장되는 반면, 덜 중요한 영역은 줄어들게 된다. 이로 인해, 일반적으로 손실률이 높은 균일 다운샘플링을 이용한 압축 후에도 작은 크기의 중요한 특징점들이 손실되지 않고 보존될 수 있다. 실측 산업 영상 데이터를 이용한 실험을 통해, 그냥 균일 다운샘플링을 이용한 압축 결과에서는 사라진 작은 기공이나 수축 균열 형태의 결함 영역이 제안 방법에서는 보존되는 것을 확인할 수 있었다. 이 변형 볼륨을 원래 형태로 가시화하기 위해선 역변형 과정을 추가로 수행해야 하지만, 이 계산은 가시화 과정에 간단하게 추가할 수 있으며, 결과를 얻기 위한 소요시간에 유의미한 영향을 미치지 않는다.Non-destructive testing is a method which examines the internal structures of industrial components such as various machine parts without dissecting them. Recently, 3D CT based analysis enables more accurate inspection than traditional X-ray based tests. However, manipulating volumetric data acquired by CT is still challenging due to its huge size of the volume data. This dissertation proposes a novel method that reduces the size of 3D volume data while preserving important features in the data. Our method quantifies the importance of features in the 3D data based on gray level co-occurrence matrix (GLCM) texture analysis and represents the volume data using a simple mass-spring model. According to the measured importance value, blocks containing important features expand while other blocks shrink. After deformation, small features are exaggerated on deformed volume space, and more likely to survive during the uniform volume reduction. Experimental results showed that our method well preserved the small features of the original volume data during the reduction without any artifact comparing with the previous methods. Although additional inverse deformation process was required for the rendering of the deformed volume data, the rendering speed of the deformed volume data was much faster than that of the original volume data.초록 i 목차 iii 그림 목차 vi 표 목차 x 1장 서론 1 1.1 볼륨 렌더링 1 1.2 비파괴검사 2 1.3 연구 내용 4 1.4 논문의 구성 6 2장 관련 연구 7 2.1 볼륨 렌더링 알고리즘 7 2.1.1 볼륨 데이터의 특성 7 2.1.2 표면 추출 기법 8 2.1.3 직접 볼륨 렌더링 10 2.2 압축 볼륨 렌더링 17 2.2.1 벡터 양자화 18 2.2.2 변환 부호화 19 2.2.3 다중-해상도 기반 기법 23 2.2.4 볼륨 변형 기반 방법 25 2.3 질량-스프링 기반 볼륨 변형 모델 27 2.4 산업용 CT 영상의 중요 특징점 측량 방법 30 3장 중요도 측정 기법 32 3.1 명암도 동시발생 행렬 32 3.2 GLCM 균일도 기반 중요도 모델 36 3.3 공기 영역 제거 44 4장 볼륨 변형, 축소 및 가시화 47 4.1 질량-스프링 모델 기반 볼륨 변형 47 4.2 볼륨 축소 54 4.3 역변형 및 렌더링 55 5장 실험 및 결과 58 5.1 화질 평가 60 5.2 속도 평가 65 5.3 파라미터 연구 69 6장 결론 74 6.1 요약 74 6.2 향후 연구 75 참고문헌 77 Abstract 83Docto

Natural ventilation design attributes application effect on, indoor natural ventilation performance of a double storey, single unit residential building

In establishing a good indoor thermal condition, air movement is one of the important parameter to be considered to provide indoor fresh air for occupants. Due to the public awareness on environment impact, people has been increasingly attentive to passive design in achieving good condition of indoor building ventilation. Throughout case studies, significant building attributes were found giving effect on building indoor natural ventilation performance. The studies were categorized under vernacular houses, contemporary houses with vernacular element and contemporary houses. The indoor air movement of every each spaces in the houses were compared with the outdoor air movement surrounding the houses to indicate the space’s indoor natural ventilation performance. Analysis found the wind catcher element appears to be the most significant attribute to contribute most to indoor natural ventilation. Wide opening was also found to be significant especially those with louvers. Whereas it is also interesting to find indoor layout design is also significantly giving impact on the performance. The finding indicates that a good indoor natural ventilation is not only dictated by having proper openings at proper location of a building, but also on how the incoming air movement is managed throughout the interior spaces by proper layout. Understanding on the air pressure distribution caused by indoor windward and leeward side is important in directing the air flow to desired spaces in producing an overall good indoor natural ventilation performance