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I have a rather theoretical question.

I connected my Raspberry Pi to my Composite NTSC TV and observed that the terminal video output has 640 pixels horizontal resolution with nice solid clear colors for text characters and logo. However, NTSC composite can only reliable produce less than 190 horizontal pixels without introducing color blurs and artifact colors (see Composite artifact colors) because of the 3.58 MHz color carrier frequency used to decode color from composite signal.

I am puzzled how they can do this. Does anybody know the answer?

  • That is a fantastic question. Really it is very interesting but I doubt we have any visual experts on the exchange... it may even be more about electronics... possibly search the electronics stack exchange or photography stack exchange for similar questions. Seems like those bunch would know a heck lot more about NTSC and all the joys associated with it. – Piotr Kula Dec 5 '16 at 19:55
  • The luminance uses the full bandwidth. The chromanance signal which carries colour information is modulated on the color carrier, and as a consequence only has ~1.5MHz bandwidth. Any good book on colour TV will explain in more detail. This isn't a Pi question. – Milliways Dec 5 '16 at 21:57
  • Did you read the question? This is exactly why I am asking it here - how Raspberry Pi managed to achieve 10 MHz resolution with 1.5 MHz bandwidth. – Andy Dec 5 '16 at 22:35
  • But this is NOT the question you actually asked. Computers can easily generate 10MHz monochrome, although this would not fit in a standard broadcast channel. This is how you can get 640 pixels; you cannot however get 10MHz colour, nor do you need it to get coloured text or logos, which only need 1.25MHz bandwidth. (You do NOT change colour on each pixel.) This still isn't a Pi question. – Milliways Dec 6 '16 at 4:03
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    I disagree. It's a question about how the Raspberry Pi works at a fundamental level. While I have no idea how composite video works, I'm voting to leave it open. – Jacobm001 Dec 9 '16 at 17:21

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