NTSC sync rate (was Re: Hewlett Packard A2094 Monitor (Standard RGB ?))

"John B" <dylanb(a)sympatico.ca> wrote: Tony wrote: John B wrote: Well, if you want to get nitpicky, the NTSC horizontal sync rate is 15.73425 KHz. The old EIA RS-170 monochrome standard was 15.750 KHz, but that is not suitable for NTSC color use. The color burst frequency is 3.579545 MHz +/- 10 Hz, and the the horizontal rate is required to be exactly 2/455 of that frequency. Otherwise the color information will produce luma artifacts and/or interfere with the sound carrier. Note that they could have chosen to make the color carrier 3.583125 MHz, and kept all the video timing exactly the same as for RS-170. Then they would have had to raise the center frequency of the audio carrier by 0.1%. The FCC apparently would not let them make that change, in the interest of compatability with existing monochrome receivers (which is incredibly stupid, since the receivers wouldn't have even noticed), so they had to lower everything else by 0.1% instead. Thus the need for disgusting hacks like drop-frame time code. Sigh. Eric Reference: _A Technical Introduction to Digital Video_ by Charles A. Poynton, John Wiley & Sons, 1996