모바일 영상통화 환경에 적합한 하이브리드 변환을 이용한 객체 기반 비디오 코덱 설계

Abstract

Recently, many people have contacted various mobile multimedia services through the mobile terminal owing to the commercialization of 3G communication technology. With the development of processing time on the mobile terminal, the video telephony has been the standout service in mobile multimedia services of 3G mobile communication. Since the service of video telephony has been provided in 3G celluar phone, 3G celluar users can use this service anywhere and anytime. But the quality of the serviced video telephony has been not good yet by the actual mobile restrictions. The user complaint about the low quality of video telephony has been raised incessantly. There are two major factors of mobile restrictions that limit to the high-quality of the video telephony in the mobile environment. The first one is the streaming bandwidth. Though the streaming bandwidth has been improved somewhat by the commercialization of WCDMA(wideband code division multiple access), HSDPA(high speed downlink packet access) and WiBro(wireless broadband), it is naturally that the bandwidth of the wireless communication is narrow more than that of the wired communication. The second one is the performance of video CODEC. The video CODEC for the service of video telephony must compute encoding and decoding at the same time. And it must process the massive video stream through software and hardware. The performance of video CODEC should be improved for the high-quality service in the existing mobile video telephony environment. The video CODEC used in the mobile video telephony environment leads to two quality problems. The first thing is the degradation in the face region under an illumination. The quality in the face region should be guaranteed in video telephony because each other speak over celluar phones seeing themselves. The second thing is the degradation in the background region with the variation. Sometimes the whole region in a frame can be greatly varied by the camera shake. When frames are encoded through video CODEC, the bit rate will be increased in the greatly varied background region and also the serious blocking artifact will be happened in that region. For solving the above-mentioned quality problems, this paper presents the design of the object-based video CODEC using hybrid transform in mobile video telephony. The proposed design firstly segment each frame into a significant object and an insignificant object and then perform separately the white valance in two objects for alleviating the quality degradation by illumination. Considering the video telephony, a significant object is set to the face region of caller and an insignificant object is set to other region except for the face region, so-called the background region. The proposed design is to improve the quality of a significant object by limiting the bit rate of a insignificant object while minimizing the quality degradation in a greatly varied background region. Thus, we compress a significant object with high quality and low compression ratio and compress an insignificant object with low quality and high compression ratio. Furthermore, we control the bit rate of the video stream in the limited bandwidth by adjusting the compression ratio of each object. From experimental results, we confirmed that our method has more higher quality than methods in the conventional CODECs at the significant region on the same bit rate.