Extended-definition television is also known as enhanced-definition television.
It is a type of DTV (digital television) format which was conceived in Japan.
The format delivers picture quality higher than standard-definition television (SDTV) but lower than high-definition television (HDTV).
EDTV-supported devices can handle video signals of either 480 lines (NTSC) or 576 lines (PAL).
This would translate to a resolution of 480p also known as NTSC-HQ and 576p for PAL or SECAM.
EDTV signals are sent over the air or through cable in analog format. When EDTV sets receive the signals, they’ll be converted to digital.
EDTV sets can also receive conventional (SDTV) broadcast signals.
EDTV sets come with DSP chips that eliminate ghost images and other image shortcomings.
Each frame is displayed as rapidly as it would on an HDTV set. But then EDTV breaks down the signals to fewer pixels. In this way, the system doesn’t have to handle a massive amount of data each second.
The transmission is done in progressive scan mode. This means that all the 480 or 576 horizontal lines are displayed in one pass.
In standard-definition television mode, the horizontal lines are displayed in interlaced mode. Lines are scanned in two passes. As such they are called 480i and 576i.
Progressive scanning offers superior picture quality.
Video is processed in a DVD player in progressive scan mode (480p or 576p). When it is delivered to a standard-definition television set, it is downconverted to 480i or 576i.
Enhanced-Definition Television Development
In the early days, EDTV in Japan came in 2 formats.
The first is EDTV-1. It has an aspect ratio of 4:3.
The second is EDTV-2 offering HDTV’s aspect ratio of 16:9, also known as EDTV-wide.
EDTV sets were once popular in Europe in the 1990s. They came with 16:9 screens, also known as anamorphic widescreen.
Thomson introduced the first European television sets with 16:9 screens with prices of around $6000. They were to support D-2 MAC EDTV broadcasts that were expected to begin in some European countries in 1990.
The strategy was to introduce a separate terrestrial EDTV system called the Philips PALplus system.
Regular broadcasts were scheduled to begin by mid-1995.
The whole idea was to get TV viewers to appreciate high-quality TV broadcasts and prepare themselves for HDTV.
EDTV isn’t recognized as an ATSC standard, though. Most HDTV developers in the USA didn’t want to adopt EDTV as a stepping stone to HDTV.
They strongly believed the adoption of EDTV would slow down the development of HDTV.
EDTV Set Example
An example of an EDTV set is the Samsung SPN4235 with EDTV (Enhanced Definition TV) picture resolution.
It promised ‘stunning’ picture quality (480p) back then when connected to a DVD player.
A notable feature is a built-in scaler designed to upconvert analog signals to 480p.
There’s also a Cinema Progressive Scan deinterlacer with 3:2 pulldown processing capability.
For a more detailed explanation of extended-definition television (EDTV), watch the video below.
Video, Speech, and Audio Signal Processing and Associated Standards
By Vijay Madisetti
Telecommunications Update, Volume 6