dtv - Computer Definition
Referring to television in digital, rather than analog, form. As is the case with digital communications, in general, DTV offers the advantages of enhanced bandwidth efficiency through compression, improved signal quality due to reduced noise, and enhanced overall management and control. DTV does not suffer from the ghosting, snowy images, and generally poor audio quality associated with analog TV. Issues of signal quality in DTV transmission manifest in artifacts such as blocking, or tiling, and stuttering. Digital video content benefits from enhanced processing, storage, and manipulation. 1 2 3 A 4 5 6 B 7 8 9 C * 0 # D Hz 1209 1336 1477 1633 697 770 852 941 More specifically, digital content advantages include editing, alteration (e.g., morphing), reproduction, compression, and store-and-forward capability. DTV standards include high definition television (HDTV) and standard definition television (SDTV). The ATSC standards specify MPEG-2 compression, and the transport subsystem as ISO/IEC 13818. Packet transport involves a serial data stream of packets of 188 octets, one octet of which is a synchronization byte and 187 octets of which are payload. This packet approach is suitable for ATM switching, as each 188-octet MPEG-2 packet maps into the payload of four ATM cells, with only 4 octets of padding required. SDTV employs Reed-Solomon forward error correction (FEC) and 8-level vestigial sideband (8 VSB) RF modulation to support a bit rate of 19.28 Mbps over a 6 MHz terrestrial broadcast channel. Audio compression is based on the AC-3 specification from Dolby Digital and the ATSC. SDTV standards were developed by the Grand Alliance and reviewed, tested, and documented by the Advanced Television Systems Committee (ATSC) at the request of the United States Federal Communications Commission (FCC). See also 8-VSB, AC-3, analog, artifact, ATM, ATSC, bandwidth, broadcast, byte, channel, compression, digital, DTV, FCC, FEC, ghosting, Grand Alliance, HDTV, modulation, MPEG-2, NTSC, octet, packet, padding, PAL, payload, Reed-Solomon, RF, SDTV, SECAM, signal, store and forward, synchronize, TV, and video.
(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, digital cable and cliff effect. p = progressive scan (non-interlaced) i = interlaced Frame Resolution 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 30p Square 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)