PDF《Now and Beyond》

Hitachi Review Vol.

55 (Mar. 2006)

11 Video Coding Technologies and Standards: Now and Beyond OVERVIEW: Video coding technology compresses digital images― composed of huge amount of data―so they can be recorded and transmitted. International standards―under the standardization bodies called the MPEG and the ITU-T―is applied to all kinds of devices, ranging from digital home appliances (like digital-broadcast receivers, DVD players and hard-disk recorders) to mobile phones. A main feature of the video coding technology that has currently become mainstream is so-called hybrid coding, which combines high picture quality with high compression performance. Nevertheless, at the standardization bodies mentioned above, aiming at attaining even higher compression and better functionality, the search for new technologies has begun. Consequently, discussions on future directions of standardization have started. Up until now, Hitachi has been actively involved in putting forward standardization proposals and developing technologies for implementing video coding technology. Moreover, at present, we are investigating ways of improving the image quality of the current H.264 coding method and looking at ways to extend its application range. This paper overviews current video coding technology, introduces the standardized technologies that we have proposed up till today, and presents some of our future research. Tomokazu Murakami Hiroaki Ito Muneaki Yamaguchi Yuichiro Nakaya, Ph.D. INTRODUCTION VIDEO coding technology is used in many familiar imaging devices―ranging from DVDs (digital versatile discs) to hard-disk recorders for storing TV broadcasts, transmission systems for digital broadcasting, DVD cameras for clearly capturing family images, and image transmission via mobile phones. Even though these devices come from different manufacturers, they can accurately record and replay images transmitted from one another, because they comply with unified international standards. International standardization of video coding Fig. 1―Standardized Video Coding Specifications by MPEG and VCEG (Video Coding Experts Group). Video coding technology has been re-standardized every several years, and every time, encoding performance has been improved. The latest coding standard, H.264/ AVC, achieves a compression performance that is two to three times higher than that of MPEG-2 used in DVDs (digital versatile discs). From now onwards, it is anticipated that developments will be aimed at H.265, which will be incorporated into the latest technologies, thereby making it easy to enjoy even higher picture quality. HD: high definition MPEG: Moving Picture Experts Group AVC: advanced video coding Picture size Coded data rate (bits/s)

10 k

100 k

1 M

10 M Mobile phone fitted with camera Streaming Normal TV picture HD picture Standardization completion period

2003 1999

1994 1992 M PEG-1 M PEG -2 M PEG -4 H .261 H .263 H .265 (to be determ ined) Com pression im provem ent H .264/AVC Development of video coding standards and performance improvement Video Coding Technologies and Standards: Now and Beyond

12 standardization. In the case of H.264, HD images can be recorded in high quality at a coding rate of approximately

8 Mbit/s;

in other words, with a 400- Gbyte hard-disk recorder, it is possible to record over

110 hours of HD images. INTERNATIONAL STANDARDIZATION ACTIVITIES AND HITACHI'

S RELATED EFFORTS Hitachi'

s Efforts Regarding Standardization Proposals Hitachi has been participating in standardization activities since the initial stages of drawing up MPEG-