Originally Posted by John Mason
Here's the B&W burst patterns
, with the frequencies added here last year. Anyone know how to convert all the frequencies into lines of resolution? --John
When you say "lines of resolution" do you mean TVL (which is lines per picture height)? Or equivalent pixel resolution? Or something else?
Equivalent pixel resolution is the easiest, since we generated the patterns via setting the pixels per cycle to even integer values. With 2 pixels per cycle (ppc), which is the highest-frequency patch, you get 1920 equivalent pixel resolution horizontally and 1080 vertically, since each cycle is one white pixel and one black pixel. The next one down is 4 pixels per cycle, which means half the equivalent pixel resolution, or 960 horizontally or 540 vertically. The next one down is 6 pixels per cycle, representing 640 or 360, and so forth. The formula is 1920 / (ppc / 2).
Frankly I think it's misleading to put frequency labels in MHz on these patterns; the numbers only ever meant something for analog video, and then only horizontally. But everyone was used to talking about the "37MHz" burst, so when vertical bursts were produced, they also got labeled "37MHz" for comparison purposes, even though there's no actual 37MHz frequency involved, theoretically or otherwise.
If you just look at the ratio between two frequency numbers, that's the same ratio as between the lines of resolution they represent. So if the highest patch represents 1920, you can calculate lines of resolution for any of the others as F * 1920 / 37.
If you want TVL, it's just the same as equivalent pixel resolution in the vertical direction, and equivalent pixel resolution times 9/16 in the horizontal direction. It allows you to compare resolution numbers between horizontal and vertical by scaling them to be equivalent. Or alternatively you can think of it as the equivalent pixel resolution of a square section of the screen.