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This is not meant to be a comprehensive introction to the history of TV, but rather a brief primer on how TVs work and why signal compression was decided to be necessary for colour broadcasts.
It still works this way today, and in many respects very little has changed. At first this seems like a horrible idea, low-resolution colour is a Bad Thing, but 'fess up: you never noticed, did you? The reasons for this are plentiful, not least of which are the deficiencies in human vision. Your eyes perceive chrominance (colour) at a far lower resolution than luminance (brightness). We all see a high-res black and white image with a low-res image slapped on top, that's how our eyes work. More or less. It's complicated, but it's true. Have a look at this image from Ogre Battle:
Click to enlarge
The black and white image is full-resolution, the colour image has been reduced in horizontal resolution by one third, and blurred horizontally to simulate the drop in resolution in an NTSC video stream. Now looking at the bottom image you might recognize the quality as something like what you normally see using AV cables; it's not so bad is it? You might be surprised how far this can go before you really notice how bad it is.
The NTSC standard allots only a small chunk of bandwidth for colour in video, and typically consumer video equipment uses less than the maximum, and what's worse is some colours have better resolution than others! TVs, VCRs and video encoders will handle different colour resolutions, and one problem the consumer has in trying to make a buying decision is specs listed for horizontal resolution are the black and white resolutions, not colour ones. Most manufacturers do not give out colour resolution for their equipment.
Chroma Compression in JPGs - Rick Matthews
Understanding Human Vision (dead link) - Clairvoyante Labs
Video Signal Formats (dead link) - CyberTheater.com
Video/TV/Computer Topics (dead link) - Allan W. Jayne, Jr.
DVD Chroma Upsampling Bug - hometheaterhifi.com
In this series:
Video Colour Resolution
Human Vision Issues
Brief History of TVs
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