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| What is HD? |
| High-definition video generally refers to any video system of higher resolution than standard-definition (SD), i.e. NTSC, PAL and SECAM. It is important to note the difference between general purpose high-definition video as discussed in this article, and its specific applications in television (HDTV), professional acquisition (HDCAM, HDCAM-SR, DVCPRO-HD & D5-HD), consumer acquisition (HDV) and optical disc systems (Blu-ray and HD-DVD). |
High-definition signals require a high-definition television or computer monitor in order to be viewed. High-definition video 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 (sometimes traditionally quoted at 2.35:1). 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 (DTV) is 486 lines (upon which NTSC is based) or 576 lines (upon which PAL/SECAM are based). However, since HD is broadcast digitally, its introduction sometimes coincides with the introduction of DTV. Additionally, current DVD quality is not high-definition, although the high-definition disc systems HD-DVD and Blu-ray are.
Below are some informative sites that explain the ins and outs of HDTV, HD video, EDTV, and other related concepts.
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