Video Quality Page

Theoretical Video Quality

Video quality varies tremendously depending on the type of signal that is fed into a television. The theoretical quality of various video signals are shown below.

Analog Video - The first three signals are analog signals.

Video home System (VHS) provides the lowest quality video on the market. People put up with it because they like the control that tapes give them. DVDs provide over twice the quality. The 320 horizontal pixels are stretched across the screen and look poor.

VHS
480 Scan Lines = Pixels	=> on 4:3 TV
	320 pixels

Black and white signals were first broadcast in 1941.

Black and White
480 Scan Lines = Pixels	=> on 4:3 TV
	440 pixels

The National Televisions Systems Committee (NTSC) standardized the color television signal in 1953.

NTSC Color = Conventional Definition Television (CDTV)
480 Scan Lines = Pixels	=> on 4:3 TV
	440 pixels

Digital Video
The following signal qualities can be provided with Digital TV. The standard quality of television is known as SDTV and provides square pixels to 4:3 aspect ratio televisions.

480i = Standard Definition Television (SDTV)
480 Scan Lines = Pixels	=> on 4:3 TV
	640 pixels

EDTV has been broadcast by FOX Networks for a number of years.

480p = Enhanced Definition Television (EDTV)
480 Scan Lines = Pixels	= on 4:3 TV
	708 pixels

DVDs provide excellent quality video. On 4:3 aspect ratio televisions, the pixels are not square but squished horizontally.

DVD
480 Scan Lines = Pixels	= on 4:3 TV
	720 pixels

Finally - HDTV. 720p is a very common format of HDTV that provides 50% more scan lines than most TV. It also packs over a thousand horizontal pixels.

720p HDTV
720 Scan Lines = Pixels 1.5 times SDTV at 60 frames per second	for 16:9 television
	1,280 pixels

1080i provides higher spatial resolution than 720p, but half the temporal resolution at 30 frames per second.

1080i HDTV

1080 Scan Lines = Pixels
2.25 x SDTV

at 30 frames per second

1,920 pixels

The HDTV signals have considerable more horizontal resolution as well as scan lines.

One confusing aspect of video quality is the horizontal picture resolution. Each scan line is stretched across the screen

TV
DTV
CDTV
SDTV
EDTV
HDTV - Spatial Resolution - Temporal Resolution - Aspect Ratio
Video Quality
Television is a very complex topic. If you would like to add some comments, corrections or additional topics, please e-mail info@broadent.com.