which is the real 4:3 NTSC resolution

[feisty2]

we have several ntsc resolutions here
720x486 (broadcast master)
720x480 (dvd)
704x480 (DV)
704x486 (??? never seen it myself anyway)
when we say ntsc is a standard using 4:3 aspect ratio, which resolution are we referring to actually? obviously it can't be all resolutions, they result in slightly different shapes when resize to 4:3 square pixel (let's say, 720x540), so, the accurate 4:3 NTSC would be the broadcast master resolution (720x486)?
Edit: I read about "overscan" on wiki, but the answer is kinda blurry

[Sharc]

we have several ntsc resolutions here
720x486 (broadcast master)
720x480 (dvd)
704x480 (DV)
704x486 (??? never seen it myself anyway)
when we say ntsc is a standard using 4:3 aspect ratio, which resolution are we referring to actually? obviously it can't be all resolutions, they result in slightly different shapes when resize to 4:3 square pixel (let's say, 720x540), so, the accurate 4:3 NTSC would be the broadcast master resolution (720x486)?
Edit: I read about "overscan" on wiki, but the answer is kinda blurry
You might find the answer here (http://forum.doom9.org/showpost.php?p=1686753&postcount=17).

[feisty2]

okay, I have seen lots of dvd videos with all 720 vertical lines filled with actual image, no blackborders
so, what should I do?
I mean
in this kind of case
4:3 refers to 720 or 704?

[Ghitulescu]

The point is that in fact it shouldn't matter, because back then the analogue TVs had overscan, and many devices (and directors) followed this restriction.
There is nobody on this Earth that can distinguish between 704 and 720 on a TV screen if there is any distortion.

[feisty2]

so, all the resolutions above can do a 4:3 image? and we should ignore the slight difference because it's neglectable?
I have always assumed 720x486 is the standard 4:3 resolution

[Ghitulescu]

For NTSC there are also another problem besides 720/711/702 etc.
The vertical resolution.
There are between 481 and 486 scan lines (including the half scanlines top and bottom), with an accepted middle value of 483, or 482 and 2 halves.

Now, again, the issue is moot as nobody would care, since:
1. overscan, of about 5-10% (as many as 70 pixels wide and 50 long are missing - what's 6 more or less)
2. the recorded signal is anyway based on 525 lines, nothing is lost.

And if you carefully read the quoted passage, you'd understand that there are no pixels in NTSC (neither in PAL), the only "digital" aspect being the fixed number of scanlines (at least for PAL).

A SVCD (Super Video CD) image is 480:480 (for NTSC) and is normally 4:3 and not 1:1. A PAL DVD has a frame size of 720x576 yet it may be 16:9.

You need to read a bit on yourself.

[feisty2]

fudged to allow either 704 or 720 pixels to equate to the full 4x3 or 16x9 picture at the whim of the author.

Although standards-compliant video processing software should never fill all 720 pixels with active picture (only the center 704 pixels must contain the actual image, and the remaining 8 pixels on the sides of the image should constitute vertical black bars), recent digitally generated content (e.g. DVDs of recent movies) often disregards this rule. This makes it difficult to tell whether these pixels represent wider than 4x3 or 16x9 (as they would do if following Rec.601), or represent exactly 4x3 or 16x9 (as they would do if created using one of the fudged 720-referenced pixel aspect ratios).

I read the quoted passage, 704x480 seems like the standardized 4:3 resolution
but the paragraph above makes things uncertain again, as we don't know 720 fully filled clips are following Rec.601 or a fudged standard
EDIT

A SVCD (Super Video CD) image is 480:480 (for NTSC) and is normally 4:3 and not 1:1. A PAL DVD has a frame size of 720x576 yet it may be 16:9.

well, my math is not that bad, I know 720 (704) : 480 (486) is not 4:3, I think you might have misunderstood me, I'm asking which resolution would produce the correct result if I just resize it to 4:3 (like 720x540 or 640x480) directly

[feisty2]

Now, again, the issue is moot as nobody would care, since:
1. overscan, of about 5-10% (as many as 70 pixels wide and 50 long are missing - what's 6 more or less)
2. the recorded signal is anyway based on 525 lines, nothing is lost.

I almost never watched DVDs on TV, I prefer to rip, encode and store them on my ultrabook so I can watch them anytime I like
so overscan is not the issue here, since full 720x480 image gets passed to avisynth via any source filter
and I watch videos on LED square pixel screen, not an analog non square pixel CRT screen/30 years ago TV, sure there's no "aspect" stuff on those CRT screens, it only comes as the pixel turns square from earlier non square
and, movies I bought, none of them is shot on analog NTSC camera, they are all shot on films, mastered at 2k/4k and downscaled to 720x480 to make DVDs
so, there's nothing about 525 (analog NTSC) involved here

[feisty2]

anyway, I don't really care about how analog videos showed on analog TVs (overscan, etc)
I just wanna know what's the correct resolution for 4:3 aspect ratio on digital square pixel screen
like, when I got a DVD, should I resize it to 720x540 directly, or add 6 pixels vertical blackborders to make it 720x486 first then resize it to 720x540

[Mole]

Why would you need to resize it? Just rip it at 720x480 and let your player resize it to whatever screen resolution your monitor is, such as 1440x1080 or whatever...

If you for some reason insist in resizing it to square pixels first, then you can just resize it straight to 720x540. As somebody mentioned earlier, nobody will notice the tiny difference in aspect with the extra 6 pixels.

I see no reason why you would need to resize it to 720x540 because if you watch it full screen on a monitor or TV, your player will need to resize it one more time from 720x540 to whatever your screen resolution is, such as 1440x1080. So you might as well preserve the quality by having the player resizing just 1 time.

Those black borders will also make your compression less efficient since it'll need to maintain the border edge.

Another point you need to keep in mind is that you can never be sure exactly how they mastered a particular DVD and if they did compensate for the overscan before they resized it to 720x480 or not.
If they for example did not, then if you add those 6 extra pixels, you may actually end up with a slightly distorted picture. Since the difference in aspect is so minuscule, chances are unless you happen to have something which is a perfect circle in the video, there's really no way for you to measure the exact correct aspect ratio of a video.

[feisty2]

well, I actually do not resize dvds, "resize to 720*540" is just an example, I just wanna know the correct 4:3 reference resolution so I can calculate the correct par value, so the player will display the correct result

[Mole]

As I told you, since there's no way for you to know how they mastered a particular DVD, there's also no way for you to know the exact correct aspect of it.

Since DVDs come as 720x480 4:3, you might as well use that. Just tell the player to resize it directly to any 4:3 resolution such as 1440x1080.

[feisty2]

okay, the answer is vague as I expected
gonna do some tests on some common commercial nle softwares (avid, fcp, smoke,premiere) and see how they handle ntsc stuff exactly

[Asmodian]

I like to assume an aspect ratio of 720x486 for NTSC as a compromise. If they followed 704x480 you get an aspect ratio error of +0.0148 (1.4667 vs 1.4815) and if they followed 720x480 you get an aspect ratio error of -0.01852 (1.5 vs 1.4815). Neither error is noticeable.

[hello_hello]

I'm not sure I've ever come across a 4:3 DVD which wasn't 704x480 = 4:3. Or at least it looks more likely to be right than 720x480 = 4:3, most of the time. Even if the whole 720 pixel width happens to be picture (or very little black borders). If that's the case I'd probably resize to something like 656x480 instead of 640x480. Of course I can't know for certain that's always correct. I just go by looking for round objects and trying to work out which aspect ratio makes them look the most "round". That sort of thing. Sometimes I don't think either is quite right, but I pretty much go with 704x480 = 4:3 all of the time.

I also believe for 16:9 DVDs it's most likely to be the other way around. There's definitely (older) 16:9 DVDs with black borders down each side that are 704x480 = 16:9, but most newer DVDs have picture over the majority of the 720 width and in my opinion they're 720x480 = 16:9. That's not a hard and fast rule but if I'm not sure I tend to assume 720x480 = 16:9.

Most software players (or all of them) assume 720x480 = 4:3 or 16:9. I'm not sure about editing software. Encoder GUIs tend to let the user decide whether to go with either an ITU pixel aspect ratio or straight 4:3 and 16:9 resizing. The only one I know of that tries to be a little clever about it is Handbrake (according to the Handbrake wiki). It assumes straight 4:3 or 16:9 resizing until a certain amount has been cropped from the sides (probably 8 pixels but don't quote me) and after that it assumes an ITU aspect ratio.

I've read HDMI DVD players can be a little schizophrenic. The aspect ratio from the component out might be ITU but for HDMI it's likely to be 4:3 or 16:9. Or maybe it's the TV making the decision. I'm not sure. I'm pretty sure when I put my TV into 16:9 or 4:3 mode (so it expects an input resolution of 720x480 or 720x576 over HDMI) it resizes to exactly 16:9 or 4:3 even though it still overscans. It's been a long time since I've thought about it, but I'm pretty sure it does. I have a Bluray player with component out. I've never tried to test whether it looks any different to the HDMI out as I almost never play discs. I watch video after I've cropped and re-encoded it and made the aspect ratio decision myself.

I should confess I've a lot more experience re-encoding PAL DVDs than NTSC so my conclusions above are based more on working with PAL discs, but I've still re-encoded a fair number of NTSC discs and I don't think they're likely to be any different.

[feisty2]

thx for all ur replies, I really appreciate it
seems nle softwares always treat ntsc as 720*486 (broadcast standard)
if u output 720*480, they will chop out 6 pixels horizontal lines
if u output 704*480, they still chop out 6 pixels horizontal lines and add display resolution 704 (original resolution 720) tags in output videos

[feisty2]

the actual image part in nle softwares is 720*483, first 2 lines of 486 are blank (there're flashing gray signal bars or something there), last line of 486 is blank too, all 720 lines are filled with image, no horizontal blank
edit: typo

[TheSkiller]

I agree with hello_hello.
I also found that 4:3 DVDs are very likely to follow the IRU-R BT.601 recommendation (704x576/480 = 4:3), even if all 720 pixels carry image; while newer 16:9 DVDs are almost always ignoring it (720x576/480 = 16:9). The latter is obvious if you compare the DVD with it's Blu-ray square pixel counterpart.

But of course, this is still just a rule of thumb. You can never be certain unless you know the origin of the video (film, SD, HD) and know in detail how it was transferred to DVD.

Or you could look out for objects known to be perfectly round and measure them in a picture editing software.

[movmasty]

But there must be a reason why dvd producers put 720 lines and not 704

and why some dvd has black stripes at the sides and some not

A reason the we didnt find out still

[Ghitulescu]

But there must be a reason why dvd producers put 720 lines and not 704

and why some dvd has black stripes at the sides and some not

A reason the we didnt find out still

It all comes from the sampling of the analogue line. SMPTE asks for 711 samples, but 711 is not dividable with 16, so it was rounded to 704. Besides, many analogue gear do not yield anyway all those 711 points as useful image. So 704 is twice recommended.

For scanned 35mm films, here one can put so many pixels as he want, as the DVD resolution is anyway much lower than the optical one of the silver film. Since the DVD requests 720 pixels for the MPEG2, scanned films are 720 as opposed to digitized (from tape) ones, which are 704.

The vertical resolution is as said before.

[Overdrive80]

Maybe this post could be useful, http://forum.doom9.org/showthread.php?p=1058927#post1058927

http://translate.google.com/translate?u=http%3A%2F%2Fencodingwissen.de%2Fspezial%2Fitur-bt601.html&langpair=de|en&hl=de&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools