Chieteuk Ahn

A VOP generation tool: automatic segmentation of moving objects in image sequences based on spatio-temporal information

The new MPEG-4 video coding standard enables content-based functionalities. In order to support the philosophy of the MPEG-4 visual standard, each frame of video sequences should be represented in terms of video object planes (VOPs). In other words, video objects to be encoded in still pictures or video sequences should be prepared before the encoding process starts. Therefore, it requires a prior decomposition of sequences into VOPs so that each VOP represents a moving object. This paper addresses an image segmentation method for separating moving objects from the background in image sequences. The proposed method utilizes the following spatio-temporal information. (1) For localization of moving objects in the image sequence, two consecutive image frames in the temporal direction are examined and a hypothesis testing is performed by comparing two variance estimates from two consecutive difference images, which results in an F-test. (2) Spatial segmentation is performed to divide each image into semantic regions and to find precise object boundaries of the moving objects. The temporal segmentation yields a change detection mask that indicates moving areas (foreground) and nonmoving areas (background), and spatial segmentation produces spatial segmentation masks. A combination of the spatial and temporal segmentation masks produces VOPs faithfully. This paper presents various experimental results.

System and Services of Terrestrial Digital Multimedia Broadcasting (T-DMB)

Commercial terrestrial digital multimedia broadcasting (T-DMB) service was launched on December 1st, 2005, in the Seoul metropolitan area of the Republic of Korea. As the worlds first commercial terrestrial mobile multimedia broadcasting service, T-DMB garnered huge attention in the field of mobile broadcasting. This paper presents the history, system, and services of T-DMB

Modeling the glottal volume‐velocity waveform for three voice types

The purpose of this study was to model features of the glottal volume-velocity waveform for three voice types: modal voice, vocal fry, and breathy voice. The study analyzed data measured from two sustained vowels and one sentence uttered by nine adult, male subjects who represented examples of the three voice types. The primary analysis procedure was glottal inverse filtering, which estimated the glottal volume-velocity waveform. The estimated glottal volume-velocity waveform was then fit to an LF model waveform. Four parameters of the LF model were adjusted to minimize the mean-squared error between the estimated glottal waveform and the LF model waveform. Statistical averages and standard deviations of the four parameters of the LF glottal waveform model were calculated using the data for each voice type. The four LF model parameters characterize important low-frequency features of the glottal waveform, namely, the glottal pulse width, pulse skewness, abruptness of closure of the glottal pulse, and the spectral tilt of the glottal pulse. Statistical analysis included ANOVA and multiple linear regression analysis. The ANOVA results demonstrated that there was a difference in three of the four LF model parameters for the three voice types. The linear regression analysis between the four LF model parameters and a formal rating by a listening test of the quality of the three voice types was used to determine the most significant LF model parameters for each voice type. A simple rule was devised for synthesizing the three voice types with a formant synthesizer using the LF glottal waveform model. Listener evaluations of the synthesized speech tended to confirm the results determined by the analysis procedures.

Moving object segmentation in video sequences by user interaction and automatic object tracking

Abstract The new MPEG-4 video coding standard consists of object based coding schemes for multimedia and enables content based functionalities. In order to apply the MPEG-4 visual standard, each frame of video sequences should be represented in terms of video object planes (VOPs). Video objects in still pictures or video sequences should be first identified before the encoding process starts. It requires a prior decomposition of sequences into VOPs so that each VOP represents an object. This paper addresses a user-assisted video segmentation method for separating moving objects from the background in video sequences. The proposed method comprises of intra-frame and inter-frame segmentation modules. The intra-frame segmentation incorporates user interaction in defining a high level semantic object of interest to be segmented and detects precise object boundary. The inter-frame segmentation involves boundary and region tracking to capture temporal coherence of moving objects with accurate object boundary information. The proposed method exhibits a consistent and faithful segmentation performance for various types of video sequences.

Experimental service of 3DTV broadcasting relay in Korea

This paper introduces 3D HDTV relay broadcasting experiments of 2002 FIFA World Cup Korea/Japan using a terrestrial and satellite network. We have developed 3D HDTV cameras, 3D HDTV video multiplexer/demultiplexer, a 3D HDTV receiver, and a 3D HDTV OB van for field productions. By using a terrestrial and satellite network, we distributed a compressed 3D HDTV signal to predetermined demonstration venues which are approved by host broadcast services (HBS), KirchMedia, and FIFA. In this case, we transmitted a 40Mbps MPEG-2 transport stream (DVB-ASI) over a DS-3 network specified in ITU-T Rec. G.703. The video/audio compression formats are MPEG-2 main-profile, high-level and Dolby Digital AC-3 respectively. Then at venues, the recovered left and right images by the 3D HDTV receiver are displayed on a screen with polarized beam projectors.

Geometry compression of 3-D mesh models using predictive two-stage quantization

In conventional predictive quantization schemes for 3-D mesh geometry, excessively large residuals or prediction errors, although occasional, lead to visually unacceptable geometric distortion. This is due to the fact that they cannot limit the maximum quantization error within a given bound. In order to completely eliminate the visually unacceptable distortion caused by large residuals, we propose a predictive two-stage quantization scheme. This scheme is very similar to the conventional DPCM, except that the embedded quantizer is replaced by a series of two quantizers. Each quantizer output is further compressed by an arithmetic code. When applied to typical 3-D mesh models, the scheme performs much better than the conventional predictive quantization methods and, depending upon the input models, even than the MPEG-4 compression method for 3-D mesh geometry both in rate distortion sense and in subjective viewing.

A design of a streaming system for interactive television broadcast

This paper describes architecture of a streaming system for interactive digital television broadcast, using MPEG-4/7 technology in delivering interactive services. The streaming system complies with ATSC (Advanced Television Systems Committee) Digital Television Standard, and delivers data of all types in ATSC Data Broadcast specification. The streaming system provides transport streams conforming to MPEG-2 systems, and has been implemented on the basis of software, and in several parts in hardware.

Enhanced-xVSB system development for improving ATSC terrestrial DTV transmission standard

This paper describes advanced dual stream system for improving mobile/pedestrian reception performance to the ATSC DTV 8-VSB transmission standard. E-xVSB system can transmit a mixture of normal (8-VSB) stream and enhanced (robust) stream. The robust stream has a higher threshold of visibility (TOV) compared to the standard stream, and legacy receivers ignore the robust packets. Thus, Enhanced-xVSB system is fully backward compatible with a current ATSC standard. For more robust transmission support, E-xVSB system adopts a reduced constellation method as well as enhanced trellis-coded modulation scheme. E-xVSB system supports a variety of enhanced modulation schemes: Pseudo-2VSB, Enhanced-4VSB, modified Enhanced-8VSB and Hybrid-VSB. Proposed system has been tested in the Lab, and the testing results are shown in this paper.

Interactive broadcast terminal system using MPEG-2 and MPEG-4

Interactive broadcast terminal system was designed for bidirectional interactive television service based on the MPEG-2/4 standards and ATSC broadcast specification. In order to implement user interactivity, MPEG-4 contents are carried by MPEG-2 PES or private section. Additional information combined as XML format is transmitted by DSM-CC data carousel while ATSC-PSIP is used to transfer the EPG information. IP is used to handle the bi-directional user interaction data through return channel.

Design of the Channel Estimation Algorithm for Advanced Terrestrial DMB System

This paper describes a channel estimation algorithm for the advanced terrestrial digital multimedia broadcasting (T-DMB) transmission system which is fully backward compatible with the conventional T-DMB standard. The advanced T-DMB has enhanced features which provide higher transmission data rate for increasing program channel capacity and better multimedia A/V service quality than the conventional T-DMB system by adopting a hierarchical modulation and scalable audio/video CODEC. To support the higher data rate transmission for the advanced T-DMB, high performance channel estimation and equalization techniques should be adopted into the advanced T-DMB receivers. In this paper, we propose a new channel estimation technique for the Advanced T-DMB to compensate channel distortion under dynamic multipath environment.