HDTV is DTV at it’s finest. HDTV is the best option in the range of DTV transmission formats.
Each of the eighteen possible broadcast formats within the ATSC standard has a specified number of active horizontal scanning lines used to create a TV picture. The greater the number of these scanning lines, the greater the level of vertical detail, in either progressive or interlaced mode. Six of ATSC’s eighteen transmission formats use 1080 or 720 active scanning lines, in either “p”-progressive, or “i”-interlaced display. This is true HDTV. The remaining twelve transmission formats use 480 active scanning lines, and are classified as Standard Definition. TV set manufacturers may also use the term Enhanced Definition (EDTV) to define the display of an SD broadcast in a 480 line progressive format. Thus Standard Definition Television (SDTV) would be any display of digital transmission, down converted to 480 line interlaced format (480i).
The following comparison chart indicates attributes of the various formats. Note that the SD, ED, and HD formats all require either an ATSC compliant built in tuner or an add-on ATSC set top box. Also remember that an ATSC compliant tuner or set top box must be able to receive and decode all 18 broadcast formats, and allow for a usable display of the picture.
|Aspect Ratio||4:3||4:3 or 16:9||4:3 or 16:9||16:9|
|Pixels per line||450 (equiv.)||708 – 720||708 – 720||1280 (720p)1920 (1080i)|
|Active lines/picture||480i||480i||480p||720p or 1080i|
|Total number of pixels||253,000 +/-||<480,000||>480,000||921,600 (720p) 2,073,600 (1080i)|
|Pictures/sec.||30||30||60||60 (720p)30 (1080i)|
|Audio||2 channel – stereo||2 channel digital||Dolby Digital||Dolby Digital|
|Broadcast Formats||1 Analogue||12 Digital formats||12 Digital formats||6Digital formats|