regarding video resolution

[Aston]

•why45 blanking lines in 1080p video resolution, why not 46

[Cornucopia]

Why NOT?
<edit> I mean, e.g. NTSC Analog is 525 lines, while the active digital area is 480 (or 486 if you were to count VITC lines), leaving 45 (or 39) lines there as well. You've got to remember, the remaining "blanking" area is strictly for live placement of the distributed image in the center of the screen. And blanking is "BLANK". It doesn't have visual content in the signal (only control content), and it only exists (now) in the last section of the chain (immediately before display).
Notice that on old CRT TVs (which the specs must still remain compatible with), the scanning electron beam starts AT REST (in the center of the screen), so to have an EVEN number of active lines and an EVEN number of buffer lines while having 2 "1/2 lines" at start and finish, you will always end up with an ODD number of lines. Even though we now have directly-addressable displays, one must remain backward compatible, so this legacy (and other quirky settings) will remain with us for some time.

Scott

[bendixG15]

I'm thrilled, this is the latest video news..........

[johns0]

Moved to Newbie / General discussions forum,doesn't belong in Latest News forum.

[Aston]

Hi Cornucopia,

From your reply I understand that, CRT TV's requires this number of blanking lines because of their Interlaced display and electron beam.
Is this right ?

And what about computer monitors, and latest HDTV's ? If these are not required these number of blanking lines, then I reduce these ?

[Cornucopia]

Historically, HDTV is built upon SDTV which was interlaced. However, interlacing has little to do with it. It has more to do with the fact that the earliest common TV display technology was CRT, which required an electron gun to sweep across the screen. I mean, it has to START from at rest, which would make it likely to be in the center (but if you did that in the VERY center of the screen it would be noticeable, so it was moved to the top). That, plus even though it is hard to notice because of the fineness of the lines, the LINES on a CRT screen are built to be just slightly DIAGONAL. That way, when the beam reaches the end of one line, it turns off and then swings back to the same place on the other side, then turns on again (takes less time - you know, shortest distance between 2 points...).
So that means that CRT-TV-based setups used this diagonal setup which left the top right and bottom left corners as half-line orphans. So rather than changing everything to make it truely rectangular, they just went with it as is. Voila! 2 x 1/2 lines = 1 extra odd line in blanking.

Computer monitors have different specs & needs (and have almost ALWAYS been progressive), but some do follow HDTV resolution specs.
However, digital doesn't really need to worry about all this, and I don't really see where you are having to even keep track of it, let alone "reduce" it...

If you stick with the standards:
HD = 1920x1080 or 1280x720 resolution @ 23.976p, 24p, 25p, 29.97p, 50i, 59.94i, 50p, or 59.94p framerate
SD = 720 (or 704)x480 (for NTSC) or 720 (or 704)x576 (for PAL) @ similar framerates (favoring the interlaced ones here)
You should be good.

You shouldn't even be dealing with or even FINDING a clip that is actually encoded 1125, etc...
With digital, all you need to be concerned with is the active (user) picture area. The rest will take care of itself.

Scott