This article explains in detail the difference between the television models SDTV and HDTV, which are part of a home theater system. Currently, there are two existing types of digital TV based on the resolution that the equipment delivers.
SDTV stands for Standard
Definition Television. As the name suggests, this type of television is capable
of rendering Standard Definition resolution. A TV resolution definition though
varies depending on a particular country where it is referred to. For instance,
the American standard NTSC has 640 x 480 pixels while the European PAL standard
for broadcasting sets it in 4:3 format with 720 x 576 pixels.
The Standard
Definitions in wide screen broadcasting (16:9) for NTSC and for PAL are 848 X
480 and 768 x 576 pixels, respectively. SD most often has an interlaced scan. An
interlaced transmission will double the apparent frame rate introduced with the
signal without getting additional bandwidth. Because the interlaced signal
contains the two fields of a video frame captured at two different times, it
enhances motion perception to the viewer and lessens flicker by making
advantage of the phi phenomenon effect.
Analog TV imposed this mode of
transmission years back to maximize usage of frequency lines which are
relatively scarce during the time. The objective is achieved by dividing the
frame into two half-frames and then sequentially transmitted 50 times per
second which happens to be the PAL standard as well. The resulting frequency
then is 50 Hz. Interestingly, the 50 Hz frequency did not occur by chance. It
happens to be relative to the minimal frequency that the human eye perceives a
continuous flow of the screen and keep its blinking seemingly unnoticed.
Despite giving 25 frames per second transmission, the human eye only perceives
them with 50 Hz frequency. It becomes a simply yet effective method of creating
a whole image on the screen without the slightest trace of blinking. “I” often denotes
interlace scan.
The other method for
"painting" a video image on an electronic display screen is called
progressive scan which is usually marked by the symbol "p". This
technique employs two fields to produce a frame. One field contains all the odd
lines in the image while the other contains all the even lines of the picture.
This new technology yields a high quality, very precise picture and is perfect
for presenting moving objects.
HDTV stands for High Definition
Television where the resolution of the signal maybe transmitted in two main
formats namely 1280 x 720 p or 1920 x 1080i. Screen format for HDTV is always
16:9 or wide-screen but it still uses either a progressive or interlaced scan.
Both plasma and LCD TV monitors are capable of showing images using these two
formats as well as the more precise 1920 x 1080p formats using the progressive
scan. If your television carries these features, then it is categorized as HD
Ready 1080p which is also ably supported nowadays by digital TV. Suffice it to
say that HDTV provides a resolution that is significantly higher than that of
standard-definition television.
A clear understanding on the
basic characteristics of televisions flooding the market ably assists a buyer
in deciding what type of TV best suits his needs and preferences. It is
worthwhile though to always consider first the resolution before taking into
account some other stuff.
Audio Impact San Diego is a home theater company that
provides assistance to those who want to setup high end home theater systems.
