! HDTV Introduction
By Richard Binckley
May 8th, 2005
Introduction
The world of High Definition TV is here and what a wonderful world it is. A bit slow to get started for my taste with some notable failures already, the most notable Voom, but I must say the future of High Definition TV looks very bright.
I got the bug back in 1998 when a local furniture store that had gotten into electronics pretty heavly combined an open house with the showing of a NFL playoff game in HDTV. This was one of the very first HDTV broadcasts in our area and being a A/V nut, I just had to see what HDTV was all about. I ended up leaving the store with a new Panasonic HDTV receiver even though I did not have a HDTV yet! I did have a Toshiba widescreen TV that looked pretty darn good with the receiver though.
Origins of HDTV
The origins of HDTV in the US go back to the late 70s when the NHK Hi-vision system was introduced to the movie industry. This analog system developed in Japan had roughly the same detail capabilities as 35 mm film, so it allowed a system that could edit movies and transfer to film much faster than conventional film editing. Eventually this system became available via satellite in Japan to the general public.
Not to be outdone by foreign competition, HDTV quickly became a political factor in the United States. At first the FCC had mandated the new HDTV standard should be compatible with the existing NTSC transmission system, but would eventually change the requirement to allow a totally new system to be used and a phase out time period for the existing NTSC system.
HDTV Broadcast Transmission
The new system would be digital primarily to allow the use of digital compression so that the HDTV information could be fit into the 6mHz slots allowed for each channel under the current FCC allotments. The analog system proposed that was similar to the Hi-vision system would require approximately 18mHz to 20mHz. The possibility of multiple channels being allocated was briefly looked at for the analog route, but at the end of the day the digital proposal won out.
Even the digital system had problems getting behind a single broadcast standard because of competing groups. Rather than settle on a single broadcast standard the FCC ended up allowing 18 different DTV broadcast standards. All would fit within the 6mHz bandwidth, so they basically decided to allow the marketplace decide which would be used.
ATSC Picture Display Formats:
|
Format |
Horizontal Pixels |
Vertical Scan Lines |
Aspect Ratio |
Scan Mode |
Frame Rate (fps) |
DTV Type |
|
1080p |
1920 |
1080 |
16:9 |
Progressive |
24 |
HDTV |
|
1080p |
1920 |
1080 |
16:9 |
Progressive |
30 |
HDTV |
|
1080i |
1920 |
1080 |
16:9 |
Interlaced |
30 |
HDTV |
|
720p |
1280 |
720 |
16:9 |
Progressive |
24 |
HDTV |
|
720p |
1280 |
720 |
16:9 |
Progressive |
30 |
HDTV |
|
720p |
1280 |
720 |
16:9 |
Progressive |
60 |
HDTV |
|
|
|
|
|
|
|
|
|
480p |
704 |
480 |
16:9 |
Progressive |
24 |
EDTV |
|
480p |
704 |
480 |
16:9 |
Progressive |
30 |
EDTV |
|
480p |
704 |
480 |
16:9 |
Progressive |
60 |
EDTV |
|
480p |
704 |
480 |
4:3 |
Progressive |
24 |
EDTV |
|
480p |
704 |
480 |
4:3 |
Progressive |
30 |
EDTV |
|
480p |
704 |
480 |
4:3 |
Progressive |
60 |
EDTV |
|
480p |
640 |
480 |
4:3 |
Progressive |
24 |
EDTV |
|
480p |
640 |
480 |
4:3 |
Progressive |
30 |
EDTV |
|
480p |
640 |
480 |
4:3 |
Progressive |
60 |
EDTV |
|
|
|
|
|
|
|
|
|
480i |
704 |
480 |
16:9 |
Interlaced |
30 |
SDTV |
|
480i |
704 |
480 |
4:3 |
Interlaced |
30 |
SDTV |
|
480i |
640 |
480 |
4:3 |
Interlaced |
60 |
SDTV |
|
|
|
|
|
|
|
Out of the 18 formats there are four that have been adopted for DTV use so far:
640×480p at 60 fps for SDTV 4:3 subchannels
704×480p at 60fps for SDTV 16:9 subchannels
1280×720p at 60fps for HDTV 16:9 subchannels
1920×1080i at 30fps for HDTV 16:9 subchannels
Notice the SDTV that would be interlaced on the analog channels are progressive on the digital channels. To my knowledge no one is using any of the interlaced formats with their digital channels.
Copyright 2005 - Richard Binckley
