Youngwoo Choi

Four-way Video Conference in Home Server for Digital Home

This paper presents a method to provide four-way video conferencing of 640times480 graphics resolution in the home server integrating the functions of high speed communication, digital broadcasting reception, and home automation applications. The home server has been designed to have the functionality of IP, terrestrial and cable STB imbedded so that it possesses a multimedia decoding module as a PCI (peripheral component interconnect) slave device to decode the audio and the video data compressed in various formats. In addition, we add a special video conference module having audio/video codec, screen divider, and audio mixer. A session manager of application program initiates and controls the additive sessions necessary in the course of participant addition from two-way, three-way to four-way. The session control is based on SIP protocol located in the processing module of the home server. The audio/video streams from each party are decoded in the video conference module. The decoded video streams are displayed on the screen divided spatially. The spatially divided video is encoded in the MPEG encoder of the video conference module and sent to destinations. The audio streams from each party are mixed so that four different mixed streams from the mixer go back to each destination with the spatially divided video. The media decoding module receives the spatially divided video and the mixed audio in formats of ITU-R 656 and I2S respectively from the video conference module

New AFC tracking algorithms for digital DBS receiver

Two new automatic frequency control (AFC) tracking algorithms are proposed for QPSK demodulation in a digital direct broadcasting satellite (DBS) receiver. These are called rotational decision directed AFC(RDDAFC) and decision device embedded AFC(DDEAFC). In order to prevent the presence of the residual phase difference by the CPAFC [Natali 1984] as well as the AFC based on the tan/sup -1/ circuit [Ishigawa 1992], the RDDAFC rotates the decision boundary for the kth received symbol by the frequency detector output of the (k-1)th received symbol while the DDEAFC uses the product of the kth received symbol and the decision device output before passing through the cross product discriminator. It is shown that the total pull-in time of the RDDAFC and PLL was 0.13 msec with a carrier frequency offset of 2.4 MHz when the S/N equals 2dB while 0.2 msec is for the DDEAFC.

Four-way Video Conference and its Session Control Based on Distributed Mini-MCU in Home Server

This paper presents a method to provide four-way video conference by distributing MCU (Multi-point Control Unit) to one of home network equipments like home server. The distributed mini-MCU consists of a special video conference module and a session manager to initiate and control the additive sessions based on SIP protocol. The media streams from each party are collected and mixed in the video conference module of the home server operating as SIP UAC (User Agent Client). The spatially divided video and three different mixed audio are encoded in MPEG-4 encoders and sent back to participants of SIP UAS (User Agent Server). Based on this mini-MCU, it is possible to provide video conference without any centralized MCUs while maintaining the network bandwidth reduced.

Self-calibration for arrayed penetrating radar

This paper describes a calibration method for arrayed radar. By using an additional pair of transmit/receive ports, online calibration for arrayed radar is possible.

Design and Implementation of Multi-participant Video Conferencing Module for a Home Server

A MVCM (multi-participant video conferencing module) with visitor identification function is working as a PCI slave device in home server. The module enables a video conference with some participants including a dweller and supports a function to identify a visitors video and audio data interworking with HAS (home automation system) in the home server. In this paper, we propose an implementation of a multi-channel, up to 4 channel, video conferencing module with the visitor identification function. The proposed MVCM uses a MPEG-4 based hardware codec (coding and decoding) for encoding and decoding participants video and audio data. The scheme is different from that in the conventional video conferencing system using software codec technology. Consequently, it has the advantage of real-time data processing.