DTV vs. HDTV
Confused about DTV? HDTV? Is there a difference? Here's a quick
description of both.
There are 18 different video formats of Digital TV (DTV). The first split is between
high definition (HDTV) and standard definition TV (SDTV).
Six of the video formats in the ATSC DTV standard are high definition TV: these are the
1080-line by 1920-pixel formats at 24 and 30 frames per second (1080i) , and at 60 fields
per second for interlaced HDTV, and the 720-line by 1280-pixel formats at 24, 30 and 60
fps (720p). The HDTV formats have a 16:9 aspect ratio.
The remaining 12 video formats are standard definition television -- not high
definition. These consist of the 480-line by 704-pixel formats in 16:9 widescreen and 4:3
aspect ratios (at the 24, 30 and 60 pictures per second rates); and the 480-line by
640-pixel format at a 4:3 aspect ratio at the same picture rates. Yes, these
include DSS and DVDs.
The formats which represent HDTV are 1080i and 720p. The "i" and the
"p" in the format names refer to interlaced and progressive scanning. In
interlaced scanning, half of the lines in a full frame are scanned onto the screen in a
sixtieth of a second, followed by the remaining half of the scan lines in the next
sixtieth. The odd lines are scanned first, then filled in by the even lines. These
are the signals broadcasted by HD transmitters from your local stations.
Bottom line is that just because a TV is labeled as DTV doesn't necessarily mean that
it is HDTV capable.
So the next time you scan through magazines or visit a local consumer electronics
store, you'll know how to decipher the facts from the sea of misinformation.