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High-definition signals require a high-definition television or computer monitor in order to be viewed. High-definition video generally has an aspect ratio of 16:9 (1.78:1). The aspect ratio of regular widescreen film shot today is typically 1.85:1 or 2.40:1. Standard-definition television (SDTV) has a 4:3 (1.33:1) aspect ratio. High-definition television (HDTV) resolution is 1080 or 720 lines. In contrast, regular digital television is 480 lines (NTSC-like) or 576 lines (PAL/SECAM-like). Current DVD quality is not high-definition, though high-definition disc systems like HD-DVD and Blu-ray are expected to be released in 2006. Historically, the term ''high-definition television'' was also used to refer to television standards developed in the 1930s to replace the early experimental systems, although, not so long afterwards, Philo T. Farnsworth , John Logie Baird and Vladimir Zworykin had each developed competing TV systems but resolution was not the issue that separated their substantially different technologies. It was patent interference lawsuits and deployment issues given the tumultuous financial climate of the late 20's and 30's. Most patents were expiring by the end of World War II leaving the market wide open and no worldwide standard for television agreed upon. The world used analog PAL, NTSC, SECAM and other standards for over half a century. NOTATION In the context of HDTV, the formats of the broadcasts are referred to using a notation describing:
For example, the format 720p 60 is 1280 × 720 pixels, progressive encoding with 60 frames per second (60 Hertz known as Hz). The format 1080i 50 is 1920 × 1080 pixels, interlaced encoding with 50 fields (25 frames) per second. Often the frame or field rate is left out. It can then usually be assumed to be either 50 or 60, except for 1080p which is only supported as 1080p24, 1080p25 or 1080p30 by consumer HDTV displays. A frame or field rate can also be specified without a resolution. For example 24p means 24 progressive frames per second and 50i means 25 interlaced frames per second. Most HDTV systems support some standard resolutions and frame or field rates. The most common are: Standard frame or field rates
COMPARISON TO SDTV HDTV has at least twice the resolution of pictures without using Letterboxing , thus further increasing the effective resolution for such content. Close-up view |
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