DTV
DTV
(Digital TeleVision) Transmitting TV using digital signals. The major DTV standards are ATSC (North America), DVB (Europe) and ISDB (Japan). All three use MPEG-2 video compression and Dolby Digital audio compression. DVB and ISDB also include MPEG audio compression (see DVB and ISDB).The FCC approved ATSC in 1996 (see ACATS), and the U.S. switched to digital broadcasting in June 2009 (see digital TV transition). Other countries have also adopted the ATSC format, including Canada, Mexico and South Korea.
A Digital TV or a Set-Top Box
To receive a DTV program requires a digital TV set or a digital set-top box for an analog TV. However, digital TV sets may continue to have analog inputs for many years, because people have huge collections of VHS movies and recordings.
Eighteen DTV Formats
DTV offers 18 digital formats (see table below) starting with Standard Definition (SD), the digital counterpart of the NTSC analog standard, except without snow and ghosts. High Definition (HD) provides 5.1 Dolby Digital Surround Sound and requires a wide screen TV set (16:9) in order to eliminate the letterbox effect.
The numerous options provide the broadcaster with a tradeoff between how many channels can be sent versus channel quality. The more HD channels, the fewer ED and SD channels, and vice versa. See digital TV transition, TV converter box, HDTV, letterbox, NTSC, 8-VSB, interlace and cliff effect.
p = progressive scan (non-interlaced) i = interlaced FrameResolution Aspect Rate Pixel Horiz x Vert Ratio (fps) Shape HDTV - High Definition TV 1. 1920 x 1080 16:9 24p Square 2. 1920 x 1080 16:9 30p Square 3. 1920 x 1080 16:9 30i** Square 4. 1280 x 720 16:9 24p Square 5. 1280 x 720 16:9 30pSquare 6. 1280 x 720 16:9 60p** Square EDTV - Enhanced Definition TV - 480p 7. 704 x 480 16:9 24p Rect 8. 704 x 480 16:9 30p Rect 9. 704 x 480 16:9 60p** Rect 10. 704 x 480 4:3 24p Rect 11. 704 x 480 4:3 30p Rect 12. 704 x 480 4:3 60p** Rect 13. 640 x 480 4:3 24p Square 14. 640 x 480 4:3 30p Square 15. 640 x 480 4:3 60p Square SDTV - Standard Definition TV - 480i 16. 704 x 480 16:9 30i Rect 17. 704 x 480 4:3 30i** Rect 18. 640 x 480 4:3 30i Square ** most popular formats RELATED FORMATS:DVD - DV/MiniDV 720 x 480 x 30 fps (NTSC) 720 x 576 x 25 fps (PAL/SECAM) Only 704 of the 720 horizontal pixels are visible. D1 Broadcast Format 720 x 486 x 30 fps (NTSC) 720 x 576 x 25 fps (PAL/SECAM)
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| SDTV vs. HDTV |
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| The 4:3 aspect ratio on standard TV and computer screens (left) is more square than the 16:9 ratio of wide screen sets (right). (Image courtesy of Intergraph Computer Systems.) |