High-definition (HD) video generally refers to any video system of higher resolution than standard-definition (SD) video, most commonly at display resolutions of 1280×720 (720p) or 1920×1080 (1080i or 1080p). This article discusses the general concepts of high-definition video, as opposed to its specific applications in television broadcast (HDTV), video recording formats (HDCAM, HDCAM-SR, DVCPRO HD, D5 HD, XDCAM HD, HDV and AVCHD), and optical disc delivery systems (Blu-ray Disc and HD DVD).
History
Original HD specifications date back to the early 1980s, when Japan developed an 1125-line TV standard operating at 30 frames per second (fps). Japan presented their standard at an international meeting of television engineers in Algiers in 1981 and Japan's NHK presented its analog HDTV system at Swiss conference in 1983. The NHK system was standardized in the United States as SMPTE (Society of Motion Picture and Television Engineers) standard #240M in the early 1990s.
The current high definition video standards were developed during the course of the advanced television process initiated by the Federal Communications Commission in 1987 at the request of American broadcasters. The FCC process, led by the Advanced Television Systems Committee (ATSC) adopted a range of standards from interlaced 1080 line video (a technical descendant of the original analog NHK 1125/30fps system) with a maximum frame rate of 30 fps, and 720 line video, progressively scanned, with a maximum frame rate of 60 fps. The FCC officially adopted the ATSC transmission standard (which included both HD and SD video standards) in 1996, with the first broadcasts on October 28, 1998.
http://en.wikipedia.org/wiki/High-definition_video
No comments:
Post a Comment