AR again

[Dogway]

hello, this is a frame of a bit strange source. The DAR of the DVD was 16:9 so assuming that NTSC 16:9 is 64:54 for Digital Content (which this seems to be) final output results to 872x480. Well that goes for the technical side, if instead I just crop and resize to 16:9 852x480, geometrics looks kinda better. What do you think I should do?


crop(2,4,-2,-8)
spline64resize(852,480)
http://img337.imageshack.us/img337/2552/01x.th.png (http://img337.imageshack.us/img337/2552/01x.png)
http://img249.imageshack.us/img249/9088/852n.th.png (http://img249.imageshack.us/img249/9088/852n.png)
http://img593.imageshack.us/img593/9761/001yrh.th.png (http://img593.imageshack.us/img593/9761/001yrh.png)

Here I try to preserve the geometry of the uncropped 64:54 translated to a new resolution adjusted by height:
crop(2,4,-2,-8)
spline64resize(872,480)
http://img84.imageshack.us/img84/4759/02x.th.png (http://img84.imageshack.us/img84/4759/02x.png)
http://img408.imageshack.us/img408/8854/872n.th.png (http://img408.imageshack.us/img408/8854/872n.png)
http://img209.imageshack.us/img209/6789/002ko.th.png (http://img209.imageshack.us/img209/6789/002ko.png)

[cacepi]

The dar of the dvd was 16:9 so assuming that ntsc 16:9 is 64:54 for digital content (which this seems to be) final output results to 872x480.

720 * 64 / 54 = 853.333333333333333

Not 872.

[Dogway]

716x468 * 64/54 = 848x468 = 872x480
Maybe Im a bit slow today...

[cacepi]

716x468 * 64/54 = 848x468 = 872x480
Let's try this again.

16 / 9 = 1.777777777777778
853.333333333333333 / 480 = 1.777777777777778
872 / 480 = 1.816666666666667

PARs are not universal; you cannot use one for all situations. When you resize the video, you change the PAR. If you wish to keep your video 716x468, you'll have to derive a custom PAR to achieve a 16:9 aspect ratio (which would be 832x468). 64/54 will not work.

[Dogway]

if source with NAB is 16/9, source with cropped NAB shouldn't be 16/9. (Although they share the same PAR)
PARs are standarized so they should be universal. Whether this one conforms it is beyond my knowledge.

[yetanotherid]

I don't care what anyone says, by far the majority of DVDs don't use the ITU resizing method.
The first lot of images look correct to me, and the wheel on the car looks round to me in picture number 3 of the first resizing method.

What format are you converting to? I'm just wondering why you don't use anamorphic encoding rather than have to think about it.
For converting to AVI I always downsize to 720 or thereabouts but using MeGUI (for example) you can encode to anamorphic output so you only need to crop and encode.... after changing the resizing method of course, as it seems there's no way to tell it not to default to the ITU resizing method, even though very few DVDs use it.

My logic would be.... resizing to the "full dimensions" and encoding with square pixels doesn't give you more resolution than if you encode using the same shaped pixels as the original DVD, but it does require more of them.

One other thought.... what container format are you using? I use MKVs mostly as they're fairly easy to work with so I don't stress about the resizing method at all. I always use the non-ITU method and if I happen to find one encode in a hundred which should have used the ITU resizing method, then I just open the MKV with MKVToolNix, change the display dimensions accordingly and re-save it as a new MKV.

[Dogway]

Yeah my question is more about object geometry than final resolution, Im still to decide on square pixel or anamorphic, I like encoding to mp4 and normally use a lil app to change PAR if necessary once encoded. My thoughts are about whether what resolution (in case of square pixel) or what PAR (in case of 720x480) should I use after crop the black borders.
I normally like square pixel because you benefit to a certain degree from the advantages of advanced resizers in avisynth and noise and left out artifacts look according. Since afterall I will resize an anamorphic 716x468 to a mod16 720x480 anyways.

RAW screenshots:
http://img141.imageshack.us/img141/899/golen.th.png (http://img141.imageshack.us/img141/899/golen.png)
http://img248.imageshack.us/img248/2097/clockd.th.png (http://img248.imageshack.us/img248/2097/clockd.png)

sample video 35Mb (I forgot to not use MU sorry):
http://www.megaupload.com/?d=UUEG0RAP

[yetanotherid]

My thoughts are about whether what resolution (in case of square pixel) or what PAR (in case of 720x480) should I use after crop the black borders.

It's either the ITU resizing method and squished looking encodes most of the time, or you take the width after cropping and multiply it by <wrong>1.777777777777778</wrong> (sorry, dumb moment) 1.422222222 to give you your square pixel width for PAL, 1.185185 for NTSC. When it comes to resizing.... how you resize depends on how many pixels you cropped, which isn't something I can know.

Is deciding on the appropriate dimensions after resizing which is the cause for concern? Personally I think life's too short to be thinking about that sort of thing, so I tend to over-crop if necessary until I've cropped to mod-16 dimensions (generally it's only a matter of losing a few extra pixels if necessary to get there) so then there's no need to resize, no risk of making a mistake and distorting the aspect ratio, and you can encode using the same number of pixels and the same pixel aspect ratio as the original DVD.
If I don't want to over-crop for some reason I tell MeGUI to resize to mod-16 dimensions and let it to the math. If you set the allowed aspect ratio error to zero in MeGUI's options it'll send the exact pixel aspect ratio required in order to produce a non distorted image to the encoder. Or I just encode non mod16.

When it comes to resizing to square pixel dimensions you either have to accept some aspect ratio distortion in order to achieve mod16 dimensions or you usually need to over-crop a bit. I was born too late for my brain to create any aspect ratio neural pathways while it was developing so I use HDConvertToX for those encodes. Once again making sure not to enable the ITU resize method I pick the required width, let HDConvertToX pick the height, and then I adjust the cropping as HDConvertToX recalculates the amount of aspect ratio distortion. I wish all encoders would do it.... but if nothing else you can use HDConvertToX to work out the required cropping for the minimum aspect ratio distortion and then use the resulting cropping in another program. Or if you do the math yourself you can at least use HDConvertToX to confirm you got it right.

I normally like square pixel because you benefit to a certain degree from the advantages of advanced resizers in avisynth and noise and left out artifacts look according. Since afterall I will resize an anamorphic 716x468 to a mod16 720x480 anyways.

I won't argue about that one as I'm not sure whether there's really any benefit there or not, but as I generally over-crop there's usually no resizing involved when I encode DVDs anamorphically. I'd be inclined to think the minute you change the aspect ratio of the pixels the benefit of anamorphic encoding is probably lost so it might be advantageous to change to square pixels, but to be honest I compared encodes using both methods a long time ago and if there's a noticeable quality difference my perception neural wiring didn't develop all that well either. Then again I tend to extend the "over-crop" philosophy to using filters too as I rarely use any. Instead I just encode the original DVD anamorphic pixel for anamorphic pixel.

[yetanotherid]

I just looked at your video (you don't de-interlace?). About 42 seconds in there's a scene with a clock pretty much square on to the camera in the background. Whatever math you used to resize the video it seems to be right, as the face of the clock is about at close to a perfect circle as you'll get.

I assume you under-crop your encodes rather than over-crop like I do? Personally I find under-cropping somewhat annoying. I like to crop till the edges of the video are nice and sharp.... but each to their own I guess. :)

[Brother John]

The DAR of the DVD was 16:9 so assuming that NTSC 16:9 is 64:54 for Digital Content (which this seems to be) final output results to 872x480. Well that goes for the technical side, if instead I just crop and resize to 16:9 852x480, geometrics looks kinda better. What do you think I should do?
If you’re really after the »correct« AR and absolutely don’t want to take any chances, then always crop to 704 width. Because at that width the ITU and non-ITU PAR both result in the same square pixel width. Problem solved. :) Of course you loose a bit of the picture on the left/right side in most circumstances.

On the topic of mod16: Do you have hardware restrictions that make this so important? For x264 encodes mod16 is irrelevant. And even with good old Xvid the efficiency loss from non-mod16 is far from dramatic. So it’s generally not worth sticking to mod16.

[Dogway]

I just looked at your video (you don't de-interlace?).
It's an unprocessed extract of the vobs. Obviously it should be right while playing it in MPHC as it reads the tagged PAR (64:54). But its not. Read on:


1. RAW Source
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_01a.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/01a.png)

2. Look the DVD is tagged as NTSC 16:9, 64:54 PAR that's a fact*, and this is what you get:
screencap
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_01.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/01.png)

3. let's imitate what hardware does:
resize(852,480)
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_02.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/02.png)
fine!

4. To crop while preserving the geometry you first crop obviously, and multiply width(or divide height) by the PAR factor (64:54). Result: 848,46 x 468
crop(2,4,-2,-8)
resize(848,468)
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_03.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/03.png)


5. which happens to have the same aspect ratio than 870,21 x 480, which in turn will be converted to mod4 872x480.
This is the DVD as it was supposed to be seen upon DVD tagged PAR, just cropped and resized:
crop(2,4,-2,-8)
resize(872,480)
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_04.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/04.png)


##########################


6. But you know what? everything from before IS WRONG because: if by nosense I decide to crop, and resize to DAR 16:9, thus messing up the DVD proposed geometry, voila, it looks correct!
Since when doing strange procedures leads to correct results? Can someone put some logic here?
crop(2,4,-2,-8)
resize(852,480)
http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_05.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/05.png)


7. *At last to mess things further, I tested with a DVD software player. It looks just like above, so my question is, whats happening in the background? Mediainfo just tells me DAR 16:9, but this is the result of a 1.162 PAR tagged source :/

http://i212.photobucket.com/albums/cc35/Dogway/Misc/th_06.png (http://i212.photobucket.com/albums/cc35/Dogway/Misc/06.png)

[mpucoder]

Neither DVDs or MPEG-2 use PAR, the "tag" is DAR.

[Dogway]

Thanks for the info, but the third image is 16:9 and is totally different from the "correct" 2 last images.

[Keiyakusha]

Thanks for the info, but the third image is 16:9 and is totally different from the "correct" 2 last images.

I don't really understand what is so surprising here. You are smarter than your hardware. You can tell that there is borders you need to eliminate, and hardware can not.

[Dogway]

@Keiyakusha: You mean that it is originaly wrong? I thought the same until the soft of the last image understood right of the hood it had to delete borders :/
I know I will use method 6, but Im trying to figure out why I am doing it so. Because there must be some standard or thinking I and MPHC are missing and others like powerDVD or the creators of the DVD are not.

[Ghitulescu]

Besides, the black borders are usually covered by the overscan.

[yetanotherid]

Besides, the black borders are usually covered by the overscan.

There appears not to be very much overscanning taking place on Dogway's monitor.

Dogway,
I haven't read through your post really thoroughly, and I've never compared the way MPC-HC resizes video with the way other players do it, but I'm fairly sure it doesn't use the ITU resizing method... while once again you are.

Do you know for a fact 16:9 means a 64:54 pixel aspect ratio or could it be 1.7777777? Edit: Dumb moment again. I referred to the DAR when I meant to ask if the pixel aspect ratio should be 1.185185 (or 1.42222222 for PAL)

Forgetting cropping and resizing for a second, an ITU resized video will appear to be squished vertically compared to a non ITU resize of the same video, or it looks stretched horizontally... it's just different ways of looking at the difference.

So you've taken a 16:9 video and assumed the media player is resizing it using the same shaped pixels you think it should be using, and if I read your post correctly you think it looks correct. But when you resize the image yourself using your idea of what the pixel shape should be it looks different/wrong? Is that correct so far?
So then it appears you cropped some pixels top and bottom, resized using a 16:9 DAR as though no cropping had taken place, and that DAR appears correct?

My guess is that by removing the black borders before cropping and resizing to 16:9, by a lucky co-incidence it just happens to be the right amount of cropping to compensate for the fact you've been assuming a 64:54 pixel aspect ratio when 1.185185 is actually the correct one, or at least the one the media player is using. Or to put it another way...

An ITU resized video will be wider than a non-ITU resized video. If it didn't use the ITU resize method then it'll look stretched a little. By removing some top and bottom pixels before resizing, then resizing as if they were still there, you've also stretched the video vertically a little and as it turns out, by just the right amount to compensate for the extra ITU horizontal stretch and return the aspect ratio to what it should be, or at least to the same DAR as the player was using.

[yetanotherid]

If my eyes aren't deceiving me...

01. non-ITU resize
02. ITU resize
03. ITU resize and cropped
04. Same as 03 but sized up.
05. Something close to non-ITU resize
06. non-ITU resize.

It's not really easy to guess which resize method is the correct one from those screen caps. It could be either. Any scenes with a nice round object in them. One which can be checked for roundness?

[Dogway]

I posted the RAW screenshot of the metro goldwin mayer for this same reason, as I couldn't find a good frontal round object. Im going to compare with another one similar in google images.
If non-ITU resize seems the correct, what kind of resize does powerDVD in last image?
And could you tell me exactly what do you mean with non-ITU resize?

This thread (http://forum.doom9.org/showpost.php?p=637718&postcount=13) discusses something similar, and Im sure that what Brother John said in post#10 (http://forum.doom9.org/showpost.php?p=1471839&postcount=10) is right, but I dont want to crop if I can fix things resizing or adding a custom PAR.

[yetanotherid]

And could you tell me exactly what do you mean with non-ITU resize?

So it does look different to the rest? I thought it was just me, or the player window was distorting my sense of perspective. I think it's non-itu(ish).

Now maybe you'll understand why I find thinking bout PAR way too hard, and why I encode anamorphically. As I said, after cropping I just let MeGUI do the math on the PAR and if later on I decide it's wrong it's easy enough to simply change it.
Square pixel encoding is often a different story though, because generally you resize to mod16 and possibly crop any extra pixels required to get you there without distorting the aspect ratio. And of course it'll be different cropping depending on the chosen resize method.
By resizing to mod16 dimensions after cropping though, and then encoding anamorphically, or by overcropping to mod16 dimensions (same cropping for both resize methods) and then encoding anamorphically you've not made any ITU/non-ITU specific resize decisions. Later on you can change the pixels to whatever shape takes your fancy and it won't make any difference (unless of course you required an exact 16:9 display aspect ratio for some reason, but generally most people don't fuss about it too much).

[Dogway]

I just want to know the REAL anamorphic ratio this film was encoded to, then the why of it (so I dont come here asking for the same). If by any matter I get to know that, later I can do my maths to crop, uncrop, resize or adding fancy PARs, always preserving the correct geometry which is what worries me most. Because Im not doing a 1:1 encode of the film, Im trying to get the most of it (restore, etc). in fact I hardly use MeGUI, only for muxing, encoding audio...
The 2 last images are what look correct to me. The rest is what my logic (and media player also) thought.

[yetanotherid]

what kind of resize does powerDVD in last image?
And could you tell me exactly what do you mean with non-ITU resize?

Non-ITU DVDs don't use the official "ITU" PAR. They simply use either 1.7777778 or 1.3333333. In my opinion, by far the majority of DVDs use the non-ITU method.

This thread (http://forum.doom9.org/showpost.php?p=637718&postcount=13) discusses something similar, and Im sure that what Brother John said in post#10 (http://forum.doom9.org/showpost.php?p=1471839&postcount=10) is right, but I dont want to crop if I can fix things resizing or adding a custom PAR.

"If you’re really after the »correct« AR and absolutely don’t want to take any chances, then always crop to 704 width."

Maybe I'm having a dumb day but it sounds wrong to me. I have no idea how you can crop to the same width while using two different resize methods and still end up with the same aspect ratio. 704 is generally used because 704x400 is as close to 16:9 as mod16 dimensions can get and 704 x 528 is exactly 4:3. Whichever resize method you use though, surely unless you crop in order to be able to resize to those dimensions without distorting the image then you're going to be distorting the image, and surely if you start from pixel shape "A" you're going to be cropping or distorting differently than if you started with pixel shape "B". Unless I'm seriously missing something.

You may find the the ITU resize gives you 704 x 400 while the non-ITU resize might get you closer to 704x416 (as an example) but I can't see how 704 is the non aspect ratio distorting, one size fits all width which fixes everything.

[yetanotherid]

I just want to know the REAL anamorphic ratio this film was encoded to, then the why of it (so I dont come here asking for the same).

You'd be better off trying to find the pot of gold at the end of the rainbow. ;) Have a look and take a guess. Sometimes, and very sometimes, the resize method will actually be mentioned in the little, bitty print on the back DVD cover, but don't hold your breath. It's one or the other though.... well at least in theory.... I sometimes wonder....

The only reason I'm fairly confident the non-ITU method is generally the resize method used it because I've got into the habit of comparing any AVI encodes I make from Bluray with the AVI encodes I originally made from the DVD, assuming of course I have DVD encodes. I haven't compared thousands, but so far I've found one (maybe two) which made me think "wrong resize method there". All my other non-ITU DVD encodes have an identical aspect ratio to the Bluray version.

The 2 last images are what look correct to me. The rest is what my logic (and media player also) thought.

Yeah you can only go by what looks right, just don't drive yourself mad trying to decide which it is as I have a couple of times. And you're not going to want to hear this, but I swear sometimes the resizing changes on the same disc. I don't even know if that's possible, maybe it's just a symptom of going mad.
I doubt the media player gave the resize method a thought. I'm pretty sure it uses the non-ITU resize method 100% of the time. I don't think there's any way for it to tell which method was used.

[Dogway]

01. non-ITU resize
02. ITU resize
03. ITU resize and cropped

Non-ITU DVDs don't use the official "ITU" PAR. They simply use either 1.7777778 or 1.3333333. In my opinion, by far the majority of DVDs use the non-ITU method.

So shouldn't the third example of post #11 (http://forum.doom9.org/showpost.php?p=1471956&postcount=11) be non-ITU resize?:
resize(852,480) that's 16:9.

[yetanotherid]

Sorry, I'm not sure I understand your last question.

[yetanotherid]

Well the first and last images look the same shape to me, and the ones in the middle all look the same too, only not the same as 01 and 06.

"So shouldn't the third point of post #11 be non-ITU resize? resize(852,480) that's 16:9."

Sorry, I think I posted some stupid a little while ago. This is why I try not to think about this stuff. Today is the most I've thought about it for consecutive minutes in a long time.
1.77777 and 1.33333 aren't the non-ITU pixel aspect ratios, they're the non-ITU display aspect ratio..... So I think the NTSC 16:9 display aspect ratio is actually 1.823169 rather than 16:9 and for PAL it's 1.823361... At least that's what MeGUI thinks.

So maybe my above resizing theory was mathematically flawed, but it probably still applies in principle, just not in a way I'll be able to get my head around at the moment (I'm very tired). I still think you're applying a different resizing method than the one your player is using, and the images themselves still look either horizontally squished or horizontally stretched to me (depending on your perspective) which generally means non-ITU and ITU resizing respectively.

I'd have to Google the actual pixel aspect ratios but I think I'm out of aspect ratio energy now. I'm sure someone else will be able to tell you what the non-ITU NTSC pixel aspect ratios are, but I'm in PAL land and I'm pretty sure I can only type pixel aspect ratio just this one last time today. Any more and my brain will melt.....

[Dogway]

Thanks nonetheless for the thinking, let me post some operations I was doing:

64/54= 1.185
1.185*720=853.33
853/480=1.777=16/9
(16/9)/(720/480)=1.185=64/54

maths are OK but it looks incorrect, the next one DOES look correct:
(16/9)/(716/468)=1.162
1.162*720=836.64

836x480 CORRECT*
1.74 ORIGINAL DAR

*Maybe it's not correct, now I see it vertical stretched o_O

I think this is a clear example of varying DAR
I have checked carefully and Im gonna stay with my original 64:54 872x480 resolution (example 5). Seems the most reasonable

[2Bdecided]

Sorry, I think I posted some stupid a little while ago. This is why I try not to think about this stuff. Today is the most I've thought about it for consecutive minutes in a long time.
1.77777 and 1.33333 aren't the non-ITU pixel aspect ratios, they're the non-ITU display aspect ratio.....They're DARs not PARs, but they're the intended DAR for ITU and non-ITU PAR - the only time they're not the intended DAR is when you have ITU PAR, but 720 pixels filled with video.

Without a real circle to look at, who knows what this really is?

Cheers,
David.

P.S. as always...
http://forum.doom9.org/showthread.php?p=1451277#post1451277
;)

[Ghitulescu]

I have to explain once more what DAR is.

Display Aspect Ratio.

The eye see the same, vertically and horizontally. In PC terms, a PAR of 1:1, in layman terms, a stick would have exactly the same length irrespective of being horizontal or vertical, and it's perceived as such.
40x30 pixels would look completely different on a EGA/CGA screen (see wikipedia for sucklings) than on a normal PC monitor.
Most people getting problems with AR are actually thinking that a pixel is, was and will always be quadratic.
Wake up, it's not. Stop saying 852x480 or 872x480, it's nothing. "Digital" PAL is 720x576 and it's perfectly 4:3 despite 720:576 is actually 5:4. So is 704x576, yet 704:576 = 1.222 or ~64/54.
NTSC and PAL work with non-quadratic pixels, like most inkjet printers. And their sizes are not really fixed, one can simply change the deflection values in the TV (EEPROM = service menu or physical potentiometers for really old sets).
The whole thing becomes more problematic as MPEG norms defines different parameters as the DVD norms, which again are different from analog NTSC/PAL standards.
Imagine that some (usually B-category) movies are telecined to tape (because the tape can be used for TV, too), then the tape is converted to DVD, maybe some video-processors are in the chain. Nobody knows the exact SAR/PAR of the image, even if using devices form the same company. But in the end DAR should be 4:3. And within some limits it is.

But strangely enough, most perfectionist questions come from people that normally don't give a damn on that their 16:9 TV sets distortely show 4:3 footage in fullscreen modus (1.78 vs 1.33), yet they argue about 64/54 versus 11/9, in other words 1.185 vs. 1.122, whereas some pixels are intentionally left blank and covered by the overscan.

That is my experience, anyway.

[mike20021969]

The eye see the same, vertically and horizontally.Unless I've misunderstood what you've said, that is incorrect.
Human's view the world in "widescreen". The peripheral vision of the eye is greater horizontally, than vertically.

[Brother John]

what kind of resize does powerDVD in last image?
Afaik all software DVD players use non-ITU PAR.

I just want to know the REAL anamorphic ratio this film was encoded to, then the why of it
Find a sufficiently large object in the movie that you are absolutely sure is perfectly round. Then measure it with different PARs applied and pick the one that’s closest to a perfect circle. That’s the only at least halfway definite solution. See Ghitulescu’s post why there might be a lot more possible values between ITU and non-ITU.

In practice you will not notice the difference. See your #27. You’re not even certain yourself in a direct comparison. The topic might be interesting to understand the details about aspect ratios. But for actually encoding video it’s close to a non-issue. The brain is too good at adapting to distortion, especially such a small one.


Maybe I'm having a dumb day but it sounds wrong to me. [...] but I can't see how 704 is the non aspect ratio distorting, one size fits all width which fixes everything.
After actually doing the calculation: you’re not alone. ... I’m sure there was a discussion about this somewhere ... Well, I guess I mixed something up. Sorry. Forget what I said.

So I think the NTSC 16:9 display aspect ratio is actually 1.823169 rather than 16:9 and for PAL it's 1.823361... At least that's what MeGUI thinks.
Yep, those are the numbers calculated with exact ITU PAR
PAL = 720 * (512/351) / 576
NTSC = 720 * (5760/4739) / 480
For the full PAR tables see here: http://forum.doom9.org/showthread.php?p=1058927#post1058927

By resizing to mod16 dimensions after cropping though, and then encoding anamorphically
I wouldn’t recommend that. One of the major reasons why we do anamorphic encodes is to avoid resizing. In almost all cases resizing to reach mod16 will hurt quality more than the efficiency loss from a non-mod16 resolution.

The peripheral vision of the eye is greater horizontally, than vertically.
You might be right. But then who uses his peripheral vision to watch movies? ;)

[Dogway]

For the full PAR tables see here: http://forum.doom9.org/showthread.php?p=1058927#post1058927
Im going to burn that post in my mind as hard as possible:)


You might be right. But then who uses his peripheral vision to watch movies? ;)

I think its said that 16:9 fills vision proportionally better (more psychovisually pleasant) than 4:3

I can try several PARs to check which one fits better (I think in the uploaded VOB there's a globe Earth Map, thats where I tested) but I got confused because the inusual black borders size, no full 720, nor 704...

[yetanotherid]

*Maybe it's not correct, now I see it vertical stretched o_O

It'd be interesting to know if it's possible/likely for different video on the same DVD to use different pixel aspect ratios. But yeah, it can drive you mad. What frustrates me... is the brain does seem to compensate quite well when it comes to a little aspect ratio distortion, so if you look at one resize method for a minute the other then looks wrong, look at the other for a minute and the first looks wrong instead.....
A few times in the past I've encoded both ways, walked away and then later on returned to open each version for a quick look, let my "gut" tell me what's right before my brain gets in the way, deleted one of them and tried not to think about it ever again.

[yetanotherid]

Most people getting problems with AR are actually thinking that a pixel is, was and will always be quadratic.
Wake up, it's not. Stop saying 852x480 or 872x480, it's nothing. "Digital" PAL is 720x576 and it's perfectly 4:3 despite 720:576 is actually 5:4. So is 704x576, yet 704:576 = 1.222 or ~64/54.

And here was me thinking we were already discussing the varying shape of DVD pixels??

But strangely enough, most perfectionist questions come from people that normally don't give a damn on that their 16:9 TV sets distortely show 4:3 footage in fullscreen modus (1.78 vs 1.33), yet they argue about 64/54 versus 11/9, in other words 1.185 vs. 1.122, whereas some pixels are intentionally left blank and covered by the overscan.

Seriously?? You think perfectionist questions come mainly from people who run 4:3 content stretched to 16:9 on their TVs and either don't care or don't notice, or on second thought is that a fairly silly generalisation? I mean, even if by some enthusiastic stretch of the imagination it could be considered true, how would you even know which way posters asking questions here happen to run 4:3 content fullscreen on their 16:9 monitors???

[Dogway]

I compared them side to side in avsp for hundred of frames (ITU, non-ITU, and the exotic example of the 2 last images). I specially tested 2 different round objects (spheres, so no perspective distortion introduced), and a few mostly trustful frames I found on google. That joined with common sense told me that here I can apply non-ITU 64:54 PAR on them, just like the row of examples from 3 to 5. It doesn't look awful in any frame like the ITU and exotic PAR did in a few frames. I have been several days checking, let's say I could be right, even if Im not.

What made my brain mess up was actually powerDVD displaying the "exotic" PAR 1.162, making me think Im missing something important.

[Ghitulescu]

Unless I've misunderstood what you've said, that is incorrect.
Human's view the world in "widescreen". The peripheral vision of the eye is greater horizontally, than vertically.

Yes! You're talking about the visual field.

If you or anyone else rotates the head so a skyscraper is horizontal, a ball will still be round. Should the metrics be different, like it is in the analog TV, it won't be round but egg-like. The objects won't change their shape ... 1 meter remains 1 meter.

The whole issue started with the first mechanical TV and continued through decades, as the "electronic" TV changed nothing to it, except that the mechanical line sweep is done electrically. The vertical axis is digital (625/525 discrete elements) while the horizontal axis is analog (and expressed in bandwidth). That's why every studio gear mentions its bandwidth, and only recently (since the PCs kicked in) started to mention lines of resolution.

The whole issue is a problem for people coming from the recent PC world, but not for those coming from the video world. As long as the output of the PC is back to tape (analog) the PAR/DAR issue (unless intentionally or accidentally screwed up) is completely transparent.

[Ghitulescu]

And here was me thinking we were already discussing the varying shape of DVD pixels??
I'm not dragging anyone into a PAR debate.
But when people say Hey, the Non-ITU looks ok but the ITU not, s/he also must say how. How did s/he see it, righly or wrongly? If it's on a modern PC (VGA and up), then the PAR is 1:1 and any image of say 640x480 would look perfect. To send this image of 640x480 to tape (eg VHS, but also Video8, Hi8, S-VHS, betamax etc.) the videocard must convert it into a SMPTE-compliant analog image, ie the 640 pixels would be transformed (dithered) into a maximal bandwith of 15.734 kHz (around 711 samples), the 480 pixels would be placed somewhere onto the visible 483 scanlines, additional lines will be added up to 525, the whole being taped and correctly displayed on any NTSC TV set.
Seriously?? You think perfectionist questions come mainly from people who run 4:3 content stretched to 16:9 on their TVs and either don't care or don't notice, or on second thought is that a fairly silly generalisation? I mean, even if by some enthusiastic stretch of the imagination it could be considered true, how would you even know which way posters asking questions here happen to run 4:3 content fullscreen on their 16:9 monitors???
That was my experience (one can also check the other posts of some users), like the common knowledge of policemen that eat doughnuts. Not every policeman eats them, but .... :p

Coming back, the DVD was created for analog TV, and apart from MiniDV, it was the best that happened to it, for the consumer market. It was not designed for PC, for PC it was its co-pendant, the DVD-ROM designed. Yet people still try to adapt it and become frustrated because they don't understand why is this. To make things more complicated, some use the same file to feed the TV via a mediatank/multimediaplayer, whose ability to understand PAR/DAR/ITU issues can only be guessed. There's no problem playing a DVD on a DVDplayer analogically connected to a SD TV. The wheels are still round (within the TV tolerances).

[yetanotherid]

Dogway,
Well I guess we got there in the end. Sorry if I confused the issue for a bit not explaining myself properly. Looking back I referred to a non-ITU pixel aspect ratio as 1.777777 a few times which no doubt made no sense to you as it doesn't make sense. I should have said 1.185185 so I edited a couple of earlier posts so anyone reading the thread in the future won't think I'm a complete idiot. ;-)

Anyway..... ITU = 875x480, Non-ITU = 853x480. I think we're on the same page now?
Of course neither give you a mod16 width. Where my brain loses interest is when it comes to working out the extra cropping. For example the ITU method really wants to be 880x480 (mod16), which means you're resizing to 880x482. Well that one wasn't too hard, I don't think. If you lost a row of pixels top and bottom and resized to 880x480 I think that'd give you the least aspect ratio distortion. For the non-ITU resize it'd be 848x480. But you can't just crop 5 pixels off to take you from 853 to 848 because you're cropping the original anamorphic pixels, so I think it works out cropping 4 pixels from the sides would be about right. Well, I guess it's not too hard when you're not resizing down to 720 etc.

Maybe I'm lazy but that's why I use HDConvertToX. I don't always use it to convert but for the square pixel stuff it's easy to work out the desired width, let HDConvertToX pick the height and then I just fiddle with the cropping till the aspect ratio distortion is down to almost zero. The only choice to make is whether to tick the ITU resize box or not. Then I use the resulting cropping for the conversion, even if it's using another program....

[yetanotherid]

But when people say Hey, the Non-ITU looks ok but the ITU not, s/he also must say how. How did s/he see it, righly or wrongly?

Do you have a link to the relevant law there?
Surely when I look at an encode and think to myself "hey, that person's head looks like someone's grabbed it and squished it down a little" I don't have to explain how I know they really weren't doing an impression of Stewie from Family Guy and ITU resizing was the wrong choice? As you said, it might be the right one or the wrong one, but unless there's a round object in the video to check, how else do you explain why you're seeing it?

Do you require the resizing to mod16 dimensions also be factored into the explanation? I'd be willing to bet I've seen a lot of AVIs which were resized "ITU" then resized to a 720, 704 width etc, so effectively the video was "ITU stretched", then "squished to 704", giving you an ITU resize that's more like a non-ITU resize, but really isn't. Maybe that's why incorrect ITU resizing isn't always as obvious as I think it should be. Just a theory for which I have no further explanation, so I hope there's no law..... ;)

[Dogway]

Of course neither give you a mod16 width. Where my brain loses interest is when it comes to working out the extra cropping.

I don't get too obsessed with mod16 resolutions. Its mainly for aesthetics and "just in case", besides it doesn't give you much room for geometry preservation. Instead I use mod4 852x480, 876x480, etc the small distortion percentage is minimal and forgiveable. But if by any mean you DO care for that minimal deviation, you can always compensate it by a custom PAR. But you must be aware that at playback the image will adjust (resize) to the defined PAR, rendering your 1:1 square pixel intention (when resizing to 852x480 for example) meaningless, so really wouldnt had been a bad idea to encode anamorphic in first place (720x480)

[Ghitulescu]

Do you have a link to the relevant law there?

What law? You may want to say maybe norm or standard or agreement or recommendation.

But I am convinced that you have no idea what DAR is. As I said before, I stop here, open your own thread on DAR if you want to continue it. :rolleyes:

[yetanotherid]

What law? You may want to say maybe norm or standard or agreement or recommendation.

Do you even follow your own posts? You made a statement:
"But when people say Hey, the Non-ITU looks ok but the ITU not, s/he also must say how."
So I asked why is that, how do you prove an opinion, or was it just a silly statement?

But I am convinced that you have no idea what DAR is. As I said before, I stop here, open your own thread on DAR if you want to continue it. :rolleyes:

After two days of discussing resizing non-square pixels in this thread and you then popping in to enlighten us all with your knowledge of the DVD pixel not being square, I really can't decide whether your claim I've not grasped a simple concept such as DAR shows your own grasp on reality is far more tenuous, or whether you're simply being a child.
Just in case you hadn't noticed, THIS thread is entitled "aspect ratio", but feel free to start your own thread on "The History of the TV Pixel, A Fascinating Journey to Analogue Tape"... if you think you'll find someone who cares.

[Ghitulescu]

Do you even follow your own posts? You made a statement:
"But when people say Hey, the Non-ITU looks ok but the ITU not, s/he also must say how."
So I asked why is that, how do you prove an opinion, or was it just a silly statement?
How would I know how a stranger (that is probably 10000 km away from me) sees the image? His image? I deducted he sees it on a modern PC, which by default has a PAR of 1, and when he means 853x480 pixels he implicitly assumes that the DAR is 16:9. As 853.33333333 / 480 is 16/9, assuming the width of a pixels is equal to its height. If he sees a PAL image of 720x576 (directly copied from a DVD) he won't see the DAR of 4:3 or 16:9, he will see the SAR (of 5:4). He didn't say milimeters, he said pixels. Should s/he be aware of PAR, s/he would have said 853 Hpixels x 480 Vpixels.
Because DAR has absolutely nothing to do with the pixels.
After two days of discussing resizing non-square pixels in this thread and you then popping in to enlighten us all with your knowledge of the DVD pixel not being square, I really can't decide whether your claim I've not grasped a simple concept such as DAR shows your own grasp on reality is far more tenuous, or whether you're simply being a child.
Just in case you hadn't noticed, THIS thread is entitled "aspect ratio", but feel free to start your own thread on "The History of the TV Pixel, A Fascinating Journey to Analogue Tape"... if you think you'll find someone who cares.
People that do not care will always be confused about PAR, DAR, SAR and stuff and they will always get into conversion problems. Leave the computer for what it was designed to do, processing data, and use the things appropriately. No video standard I know was designed with personal computers in mind, implicitly or explicitly. As this thread shows, the HW players have no problems at all doing things a SW fails -> http://forum.doom9.org/showthread.php?t=159158&highlight=avatar. If I would have enough time I would find for each and one aspect of A/V processing such a thread.

Should nevertheless the user be determined to convert a DVD into a space-oriented format to be watched on a computer, I strongly suggest her/him to do some visual tests with various settings (PAR and cropping) before the real encoding step.

[2Bdecided]

Yep, those are the numbers calculated with exact ITU PAR
PAL = 720 * (512/351) / 576
NTSC = 720 * (5760/4739) / 480
For the full PAR tables see here: http://forum.doom9.org/showthread.php?p=1058927#post1058927There's nothing exact about the "exact" numbers there. They're more wrong than the common approximations.

The absolutely correct ITU PAL PAR is 1150/1053=1.09211775878
The very common and good enough approximation is 12/11=1.0909090909
The supposedly "exact" number above is 128/117=1.09401709402

I'll be the first to admit that this discrepancy doesn't matter - it's one pixel - but it irks me to see someone say "this more complex method is more exact" when the dead simple and far more common method is actually more exact!


Reality isn't that complex. I'll provide the link yet again
http://forum.doom9.org/showthread.php?p=1451277#post1451277
...and another...
http://forum.doom9.org/showthread.php?p=1100187#post1100187

Cheers,
David.

[2Bdecided]

Because DAR has absolutely nothing to do with the pixels.Well it does on the square pixel PC displays most of us are using to type messages onto this forum. You can do the measurement it in pixels or cm and the result will still be the same - because when you divide one number by another, the units cancel ;)

(I know PC displays don't have to be square pixel, but most are. The days of non-square-pixel LCD "H"DTVs are over too, so I don't know who is buying non-square-pixel displays that work with PCs these days)


No video standard I know was designed with personal computers in mind, implicitly or explicitly.FLV? ;)

Cheers,
David.

[Ghitulescu]

FLV? ;)
And this corresponds to which SMPTE or ITU-R or EBU? :rolleyes:

[Groucho2004]

And this corresponds to which SMPTE or ITU-R or EBU? :rolleyes:

How is this related to your statement?

[Ghitulescu]

In case you read only the last line, please notice that my answer was a comment to a comment to a statement of mine.

I'll repeat the statement for your comfort - no video standard was ever created with the PC in mind. One would not find any reference to the PC platform, nor limitations thereof, in any of SMPTE/IEE/JIT/AES/EBU/ITU-R and so on, concerning video and/or audio. Of, course, there are common features a PC shares with RISC CPUs and GPUs used in standalones or studio gear.

But this seems to go off topic. ;)

The topic was: what to use?

The answer is: it depends. Someone provided a list of DAR/PAR values, for some usual cases involving a DVD and its possible origin. Also whether cropping/resizing is needed or not. This list is somewhere in this forum, in thread concerning DAR and PAR.

[Brother John]

There's nothing exact about the "exact" numbers there. They're more wrong than the common approximations.

The absolutely correct ITU PAL PAR is 1150/1053=1.09211775878
The very common and good enough approximation is 12/11=1.0909090909
The supposedly "exact" number above is 128/117=1.09401709402
Interesting ... so those two half lines make another difference. I’ve never heard about that. Then let me do a:
post#31.replace("exact", "somewhat approximately exactish");

Do you maybe have any links or other resources with more details about that issue? Google didn’t turn up anything besides your posts here on Doom9 and I’d really like to wrap my head around this completely.

[Ghitulescu]

Interesting ... so those two half lines make another difference. I’ve never heard about that. Then let me do a:
post#31.replace("exact", "somewhat approximately exactish");

In this post of yours that you refer to few posts above you did commit a series of errors. - http://forum.doom9.org/showthread.php?p=1058927#post1058927

First of all, that SAR is another name for PAR. This seems to be a common mistake. Even your calculations contradict you.

No, the pixels in the sample (new term) or storage (old term) frame have nothing to do with the pixels in the displaying device (PAR/DAR). Now that HDTV is a reality, the PAR of any FullHD display is 1:1, and the A/V chain would translate those 720x480/x576 pixels into 1920x1080 ones.

DAR governs what is displayed, SAR governs what is stored/recorded. PAR refers to display.

The second one are the values. They are approximations, the good ones are deducted from timings (remember, the analog standards have no pixels, the only "digital" thing being the number of scanlines, and the teletext of course :p) and bandwidth.

The third one is difficult to be spotted because people generally interpret the images. They know that the top/bottom bars (matting) or the pillarbox sidebars are not part of the image. And because of this, they got tricked into thinking that a spaghetti western has a DAR of 2.35:1. False! The DAR cannot be anything else than 16:9 or 4:3. For 2.35:1 to be achieved, black bars are added (and for 16:9 the image would be anamorph encoded, and the bars would be thinner). One sees this if the image has subtitles - on a proper DAR these cannot be outside of the image :p:p:p:p:p:p:p:p:p:p like it's usually the case.

[GodofaGap]

First of all, that SAR is another name for PAR. This seems to be a common mistake.
Excuse me, but in H264 what you call PAR is called SAR. SAR stand there for sample aspect ratio (for reference check the x264 setting for anamorphic video) and a sample is in principle just a more generic word for pixel.

[cacepi]

There's nothing exact about the "exact" numbers there. They're more wrong than the common approximations.
And let's not forget that the SAR values for MPEG-4 are only valid for cropped images:

For the examples in Table E-1, the term "without horizontal overscan" refers to display processes in which the display area matches the area of the cropped decoded pictures and the term "with horizontal overscan" refers to display processes in which some parts near the left and/or right border of the cropped decoded pictures are not visible in the display area. As an example, the entry "720x576 4:3 frame with horizontal overscan" for aspect_ratio_idc equal to 2 refers to having an area of 704x576 luma samples (which has an aspect ratio of 4:3) of the cropped decoded frame (720x576 luma samples) that is visible in the display area.

In other words, 12:11, 16:11, 40:33 and 10:11 all assume a cropping rectangle of the clean aperture only (or "active picture" or whatever you want to call it... 704x480 for NTSC, 704x576 for PAL).

Hard as it is to believe - as the concept seems loosely understood on this thread - 16:9 really does mean 16:9.

[yetanotherid]

How would I know how a stranger (that is probably 10000 km away from me) sees the image? His image?

Having a conversation with you is like trying to determine the PAR used on a DVD, while banging your head against the desk.
Once again, you said:
"But when people say Hey, the Non-ITU looks ok but the ITU not, s/he also must say how. How did s/he see it, rightly or wrongly?"
And once again, I'm asking... why must they say how, and how do they prove prove what's usually just an opinion as to which method looks right?
I've no idea how you'd know why a stranger 10000km away from you sees one method as correct and the other wrong, but I'm equally baffled as to what it might have to do with the question. Unless your day job has you employed as the PAR police?

People that do not care will always be confused about PAR, DAR, SAR and stuff and they will always get into conversion problems. Leave the computer for what it was designed to do, processing data, and use the things appropriately.

On dear.... not that old chestnut again??? Please define "data" because I was under the impression the PC can't process anything else.
Just in case you hadn't noticed, and your odd "PC for processing data" theory aside, in the real world people use their PCs for converting video all the time, including DVDs, so naturally there will be discussions as to how to achieve the best result, including the determination of PAR. Living in denial as to whether they should be doing so is irrelevant. It's time to accept it and move on.
Just in case you also hadn't noticed, the people posting here don't fall into the "don't care" category anyway, so your point is irrelevant in two completely different ways.
And why are you posting in a thread discussing the subject of converting DVDs with a PC if you think people shouldn't be doing it? Surely there must be more appropriate threads for you to post in, such as they best way to convert video with your toaster, or whichever appliance it is you use for the job?

Should nevertheless the user be determined to convert a DVD into a space-oriented format to be watched on a computer, I strongly suggest her/him to do some visual tests with various settings (PAR and cropping) before the real encoding step.

Just out of curiosity, have you read any of this thread, because if this thread's not about experimenting with visual tests and various settings, I'm curious as to what you think it's actually about?

The third one is difficult to be spotted because people generally interpret the images. They know that the top/bottom bars (matting) or the pillarbox sidebars are not part of the image. And because of this, they got tricked into thinking that a spaghetti western has a DAR of 2.35:1. False! The DAR cannot be anything else than 16:9 or 4:3. For 2.35:1 to be achieved, black bars are added (and for 16:9 the image would be anamorph encoded, and the bars would be thinner).

These "people" you refer to, it sounds like another gross over-generalisation to me. It might be a mistake someone new to encoding would make once, and probably not make again.

One sees this if the image has subtitles - on a proper DAR these cannot be outside of the image like it's usually the case.

Usually?? So it wouldn't be hard for you to provide an example?
Are you sure it's not a case of the video having been encoded with a PC, the subtitles placed below the image (which can be done), and your "never use a PC for converting video" phobia has you making incorrect assumptions regarding the DAR?

[manono]

Excuse me, but in H264 what you call PAR is called SAR. SAR stand there for sample aspect ratio (for reference check the x264 setting for anamorphic video) and a sample is in principle just a more generic word for pixel.
And the H264 people took an acronym that already had a perfectly good definition and redefined it to mean something else, thus confusing the issue. For me and many others SAR stands for Storage Aspect Ratio. Why redefine what the letters stand for when PAR already exists?

And yetanotherid, your sarcastic attitude will either stop immediately or you'll be struck. If you have something to say, say it politely. I'm removing the second of your two posts above. Don't respond in kind, Ghitulescu.

[Ghitulescu]

Usually?? So it wouldn't be hard for you to provide an example?
Are you sure it's not a case of the video having been encoded with a PC, the subtitles placed below the image (which can be done), and your "never use a PC for converting video" phobia has you making incorrect assumptions regarding the DAR?

I'll try to provide some images, provided they will be quickly approved.

[yetanotherid]

And yetanotherid, your sarcastic attitude will either stop immediately or you'll be struck. If you have something to say, say it politely. I'm removing the second of your two posts above. Don't respond in kind, Ghitulescu.

Well I've read through my post again several times, and I'm at a loss as to your definition of sarcastic.
Personally I think I showed great restraint given I'd been discussing DVD PAR in a PAR thread for two days, only to have the resident PAR expert pop in to enlighten us with his knowledge of DVD PARs not being square, explain we shouldn't be converting DVDs with a PC, and then proceed to tell me if I wanted to continue discussing PAR I should start my own thread. Pity none of it helped the OP answer his actual question, but I guess of you give me a strike next time it'll have to do while I happily spend my time doing something else.

[GodofaGap]

And the H264 people took an acronym that already had a perfectly good definition and redefined it to mean something else, thus confusing the issue. For me and many others SAR stands for Storage Aspect Ratio. Why redefine what the letters stand for when PAR already exists?
That may be true (although storage AR is something of questionable use), but it is rather irrelevant to the point made.

[Ghitulescu]

Excuse me, but in H264 what you call PAR is called SAR. SAR stand there for sample aspect ratio (for reference check the x264 setting for anamorphic video) and a sample is in principle just a more generic word for pixel.

SAR is used to obtain a usable image using the information actually stored. For instance, valid frame sizes for DVD MPEG-2 are 352x, 704x and 720x576 (for PAL). That means the actual PAL image of a single scanline was compressed to be stored on 352, 704 or 720 pixels. How many pixels has a PAL scanline? Well, none. How many samples has 1 second of music? Still none. Based on spectral analysis, frequency response of the tape based systems and using technical common sense, it was established, but this only after digitalisation came into the video world, that it makes sense to have 702 samples on a PAL scanline, and 711 on an NTSC scanline. Still no 352, 704 nor 720, but 701(some decimals here) and 711(some decimals here too). How on hell did those values appeared?
Well, any digitizer is based on binary logic, like the PC, and since 8 and 16 were already in use in computers as well as in micro electronics, it made sense to the standardizing bodies to accept those values. 712 (the most close 8multiple to 711) was not chosen, instead 704 and 720, for the same reason why 44kHz1 was chosen for CD audio. And 704 was used to digitize analog PAL signals (close to the 702 samples).
Why 352? Because it's 704/2 and Philips thought that this is the theoretically resolution of the VHS system (corrected with the kell factor). JVC took this info in the NTSC world.
A perfect playing device needs nothing more than the storage frame size and the DAR to output a perfect PAL/SECAM signal. Because it simply need to enlarge the horizontal signal (based on the line length in storage pixels) to 711/702 samples. It's exactly the same principle as used in stretching/shrinking the audio from one standard to the other (PAL <-> NTSC). And, like in music, when one senses the wrong pitch, one can sense the wrong DAR.
The signal travels the wire and reaches a display device. What does the device do? Take the signal and stretches it to fit its native resolution. And what if the image be distorted? Then the is an incompatibility between the PAR of the source and the PAR of the display (provided the DAR is the same for both, ie 4:3 signal, 4:3 display or 16:9 source, 16:9 display). Then the device takes the signal, corrects it with PAR (display PAR), then fits it in the native resolution. It should be a perfect fit, if the PAR was correctly calculated. Is the signal in another DAR? Then the DAR is transported along (WS signalling) or the correction is done internally in the playing device. On top of this, and to partially correct some issues, came SDE, usually called Pan&Scan, which takes only one portion of the stored frame to display (logical matting).

Why is there so much confusion in the PC world?

Because the signals are no longer converted into well established standards ("wire transport" is missing). And thus the PARs for both must be recalculated, generally for a display PAR of 1:1. This is why the old term of Storage aspect ratio was changed into Sample aspect ratio. Simply because one known factor, considered to be fixed, is no longer fixed in the PC world.
As I said, it was necessary to have only the frame size (actually the line width in sampling points/values) and the DAR to be able to reconstruct a perfect NTSC/PAL signal.

But in computer world, when a video has 800x500 pixels, there's no way of knowing what kind of standard is this (remember, it also lacks the fps element). Is it 4:3, or maybe 16:9, was it cropped, or maybe matted? It can't be fit in any of the TV standards without serious "patching" (cropping to 640x480 (assuming a PAR of 1) then sending it as 720x480 through the wire to the TV; or maybe adding black borders around to become 852x576 then send it as 720x576 through the wire with WS flag set).

Why do I mention analog?

Because a DVD is not born a DVD. Is born in the analog world, be it film (that has to be scanned) or Live TV (that has to be digitized). Even the digital recorders/camcorders are analog compliant. And thus these limitations has to be known.

People that process their own recordings, digitally made, like all these HD camcorders, smartphones, digital photocameras and the like have next to no problems. Such problems encounter those that care enough about quality yet they stubbornly insist in converting into a digital-only format.

My advice? Wanna backup your DVD collection? COPY/PASTE.

[GodofaGap]

This is why the old term of Storage aspect ratio was changed into Sample aspect ratio.
No no and no. People are using SAR the same as PAR here because it is defined H264 that way, and you are not going to weasel your way out of your uninformedness by posting a large blob of text.

Those people aren't making a mistake like you said.

[Ghitulescu]

Are you replying for the sake of replying? Do you read more than one line from a post?

Please look for the word H.264 (or its equivalents) in the original post.

The OT was what AR should a DVD have it when displayed on a PC monitor. In green my deductions, he said pixels so I assumed he thought the pixels are equally big on both axis. And the DVDs originates from the analog world, where standards must be obeyed. A DVD-video cannot have any other codec than MPEG-2 (and MPEG-1 for assuring VCD compatibility).

[GodofaGap]

Are you replying for the sake of replying? Do you read more than one line from a post?

Please look for the word H.264 (or its equivalents) in the original post.
Your comment that SAR was not used correctly did not refer to the original post of this topic. It referred to a post in a different topic that was definitely about H264.

In this post of yours that you refer to few posts above you did commit a series of errors. - http://forum.doom9.org/showthread.php?p=1058927#post1058927

First of all, that SAR is another name for PAR. This seems to be a common mistake. Even your calculations contradict you.

Now try again. And who is not reading?

[Ghitulescu]

You're right, but this notion was used to obtain some values, to support a certain crop/resize method.

Anyway, I'll stop here, not without mentioning that the exact values are not really important, as long as 853(decimals) or 852(decimals) or even 854(decimals) - values computed using various PAR values - must be anyway rounded to the nearest multiple of 4/8/16 as required by the encoding codec.

[Dogway]

My advice? Wanna backup your DVD collection? COPY/PASTE.
Rather than backup, I want to restore...



The OT was what AR should a DVD have it when displayed on a PC monitor. In green my deductions, he said pixels so I assumed he thought the pixels are equally big on both axis.

I always check my monitor pixel ratio is 1. The question was more about what kind of NAB has this source that fits into any standard, and therefore which PAR should it match to.

[Ghitulescu]

Then I misunderstood your question.

You want to "restore"? As opposed from "degrade" but not from "save"?

If you intend to repack the "restored"/processed movie back on DVD, you don't need to touch anything - do your restorations taking into account several limitations (interlaced, chroma upsampling bug etc.) without any resize/crop etc. Then save it back on a DVDR [DL] and be happy.

[Dogway]

why should I use a lower profile codec when technology provides me with an advanced industry supported one (h.264)? Excepting raw film, analog world is getting behind the digital.
You talked a lot about 704 pixels wide, but this film was 716, I want to know if the guys who made this DVD made any mistake (as through the time Ive been around here I have seen many official DVD's are wrong, and this one isn't really really official at all)

[Ghitulescu]

I said it before and I 'll say it once more: the DVD is the best what happened to the SD video for consumers (MiniDV for camcorders), the almost perfect combination of price, handling, quality, features and not least size.

Yet the medium and the format have both flaws. Some of these flaws are difficult to be treated correctly, usually what's done is masking.

Like it was the case in the 90ies, when a lot of "lost" movies appeared on VHS and people feared that these movies will be lost again, forever, now it happens the same with the DVD. Those movies appeared again on DVD, in a much better quality (anyway, better than could do Average Joe), depending on the source.

If a movie has the potential to attract watchers or belongs to so "cult movies" for various population groups, it will be rereleased on BD, in a better quality than Average Joe would obtain.

Unless the movie has to be immediately watched/used, there's no hurry to do this. My opinion.

[Dogway]

My question is not only for this source, but in general, for learning purposes (through practical examples). Digital media formats playback is a reality, I see it in Zune (Xbox360), iTunes, Steam(?), and many other online or on-demand systems.
I dont say the idea of DVD is bad, its good at its conception, but like everything it might be bad executed. That's what many threads are about; "how can I fix this source?"
BD releases depend on potential profit, not exactly on cinematographic, artistic, cult, or human values (although its sometimes linked). And I don't see this film ever released on BD.

Edit: I agree you can have your own opinions but I opened this thread to discuss an specific AR issue. I wouldn't like this to derivate into an offtopic debate.

[henryho_hk]

Storage Aspect Ratio = "Number of horizontal pixels" : "Number of vertical pixels"
Sample Aspect Ratio = Pixel Aspect Ratio = "Width of a pixel" : "Height of a pixel"
Signal Aspect Ratio = Picture Aspect Ratio = Display Aspect Ratio = "Width of picture displayed" : "Height of picture displayed"

................. I have a headache .................

[Gavino]

Sample Aspect Ratio = Pixel Aspect Ratio = "Width of a pixel" : "Height of a pixel"
Just to muddy the waters further :), let me say that the term Pixel (or Sample) Aspect Ratio is a bad name (although it's too widespread now to correct the 'misuse').

Pixels (as represented in a digital storage medium) don't have a width and height - they are point samples. The correct term should be Pixel Spacing Ratio. The distinction may seem academic, but it causes immense confusion when trying to understand what really goes on during resizing (ie resampling to a different sampling grid).

See Alvy Ray Smith's classic 1995 paper: A Pixel Is Not A Little Square (http://alvyray.com/memos/6_pixel.pdf)

[henryho_hk]

No, I don't agree with you. Pixel, being a sample of the picture, has a shape, and thus width and height. Point hasn't (by definition). Pixels' shape is defined by the point spacing (or sampling).

The term "Point Spacing Ratio" is a good idea. ^___^

[Ghitulescu]

No, I don't agree with you. Pixel, being a sample of the picture, has a shape, and thus width and height. Point hasn't (by definition). Pixels' shape is defined by the point spacing (or sampling).

The pixel is a display unit, not a recording one.

Gavino is right. During the acquisition, the luma is sampled at 13.5 MHz, that means the instant amplitude value of the signal is captured. And, like audio, during play, in analog domain, the samples are outputted at the same rate (13.5 MHz) and the resulting video amplitude "interpolates" the points/samples.

However, on a PC, one needs pixels. Otherwise the image of a Bitmap would look like Milky Way (the galaxy) :p. So, by convention, the screen was filled in.

So by CRTs. The height of the "pixel" is given by the thickness of the electronic spot. Try to adjust its diameter, like one does in an oscilloscope, and you'll see the raster.

[mpucoder]

"A pixel is not a little square" is another topic of debate as it depends on how the image was sampled. Digital cameras do not sample points, the sensors have definite size. ADC systems sampling at 13.5MHz (ITU601) may appear to sample a point in time as they use sample and hold circuits, but the signal has been through a low pass filter which smoothes the values, therefore spreading the sample out over a short distance in time. Vertically even analog camera scan lines have thickness.

But Ghitulescu brought up a good point that everyone seems to have ignored. The active area of NTSC is NOT 704x480, and PAL is NOT 704x576. He mentions the correct horizontal sampling of approximately 711 for NTSC and 702 for PAL. Only approximate because the number of samples in a scan line is determined by the sampling rate (13.5 MHz) and the appropriate analog standard definition for the active area. The vertical active area is also different from the digital standard, NTSC lost 5 scan lines in the move to the digital domain. These lines were part of the image shot a 4:3.

Now in the DVD world there are multiple paths to a DVD. It could come from analog television cameras or telecined movies, in which case the active area for NTSC would be 711x485. Or it could come from film or CGI and be 720x480 (ignoring the older ITU standard and using the full capability of the media). These are the two most common.

Dogway mentioned the scan lines appear to have 716 samples per line. This could come from timing errors in the source. Older analog cameras have analog adjustments for sync pulse, back porch, and blanking area that need to be calibrated periodically. Most digitizers will encode 720 samples per line to allow for timing errors (horizontal skew - the blanking area may be the correct width, but not aligned correctly with the sync pulse, moving the image left or right a few samples).

[yetanotherid]

why should I use a lower profile codec when technology provides me with an advanced industry supported one (h.264)? Excepting raw film, analog world is getting behind the digital.

None that I can see. Given you're "restoring" and therefore eventually re-encoding anyway, why would you keep the video in some archaic format when you can convert it one which will play on a larger number of devices, and take up far less space for a given quality? I don't see one person's obsession with not using a PC to transcode an anamorphic video to square pixels as a good enough reason, especially when as far as I'm concerned he's not offered any logical reason for not doing so.
So what if there's a decision to be made regarding the resizing? I don't see how on one hand someone can write an essay on the various ways the DAR can be fudged when recorded and displayed in the analog world, then on the other use that as the very reason for not trying to get it right when converting in the digital world. It makes no sense to me.

Personally, if I was "restoring" a DVD or any other format, my last choice for output format would be DVD again. I've not backed up a DVD to DVD format for years. Why would you?
Is there even any guarantee the software you're using to re-encode the DVD you're restoring will use the same PAR as the original source?

I agree you can have your own opinions but I opened this thread to discuss an specific AR issue. I wouldn't like this to derivate into an offtopic debate.

Good luck with that. ;)

[yetanotherid]

But Ghitulescu brought up a good point that everyone seems to have ignored. The active area of NTSC is NOT 704x480, and PAL is NOT 704x576. He mentions the correct horizontal sampling of approximately 711 for NTSC and 702 for PAL. Only approximate because the number of samples in a scan line is determined by the sampling rate (13.5 MHz) and the appropriate analog standard definition for the active area. The vertical active area is also different from the digital standard, NTSC lost 5 scan lines in the move to the digital domain. These lines were part of the image shot a 4:3.

I don't know if it's a case of ignoring it, or (in my case) failing to see the relevance it has to this topic.
So I'm converting a DVD to AVI or x264 etc. I crop the non-picture area, choose a pixel resizing method and encode. Sure, if for some reason I still don't think it looks right I can resize the whole image slightly to compensate, but in what way exactly should I be stressing about active picture area and number of scan lines before I do?

I'm actually interested to know, because I'd like to know where I went wrong when encoding a DVD of an old TV series recently. In reference to the active picture area, the were sections within a single episode which required virtually no cropping, some where I needed to crop 20 or more pixels from one side and only a few from another, and some where I had to crop nearly 30 pixels from each side. So I cropped by an amount which removed the non picture area from a whole episode, picked the resizing method which seemed correct (non ITU) and encoded. What else should I have done?
(And no ....because I know it's inevitable.... I'm not interesting in hearing about the overscanning when watching the video on a display I'm never going to use).

In fact it's those recent encodes which prompted me to mention I sometimes think there's more than one PAR or DAR used on a single DVD at times, because while the majority of the time I think the non-ITU resizing was correct, there's a few times when it seemed like it wasn't. But what do you do, drive yourself mad trying to chop an episode into sections and crop and resize each differently, then try to join all the bits together?
And even if I'd left the whole thing on the DVD because of a phobia of re-encoding to play the video on another device, if there were different resizing methods used in sections of the DVD, does my dragging an old CRT TV out of the shed to display them somehow fix them?

I am curious to know, because at the moment I can't find a way to see advice not to transcode a DVD to another format as anything but silly. And for the record, aside from having cropped the crud, my encodes looked identical to the way the original DVDs were being displayed when viewed side by side on my monitors (MPC-HC). I don't know if the same thing would apply to watching them on a CRT or LCD TV, but it's irrelevant to me, because I never use one.

[2Bdecided]

Interesting ... so those two half lines make another difference. I’ve never heard about that. Then let me do a:
post#31.replace("exact", "somewhat approximately exactish");

Do you maybe have any links or other resources with more details about that issue? Google didn’t turn up anything besides your posts here on Doom9 and I’d really like to wrap my head around this completely.I don't have any links justifying my calculations. They were from first principles, like yours.

However, scanning on an analogue CRT is (theoretically) like this...
http://www.pembers.freeserve.co.uk/World-TV-Standards/Line-Standards.html#Vertical
...giving a picture with a height of 575 lines - the half width lines turn out to have effectively half height too.

I'm not sure what point Ghitulescu is trying to make.

Cheers,
David.

[2Bdecided]

And this corresponds to which SMPTE or ITU-R or EBU? :rolleyes:Once we have square pixels (SMPTE 274M and 296M), progressive scanning (ditto), same colours (sRGB vs Rec.709), and same gamma, I fail to see how you can say the standards target or don't target PCs. They define a video standard. To say the authors didn't anticipate PCs at all in the late 1990s and early 2000s seems a strange claim indeed.

The sample rate of CDs is tied to analogue VCRs - but I'm damn sure that the Yellow Book and Orange book anticipate PC use, while keeping the "legacy" sample rate.

Cheers,
David.

[2Bdecided]

And let's not forget that the SAR values for MPEG-4 are only valid for cropped images:
For the examples in Table E-1, the term "without horizontal overscan" refers to display processes in which the display area matches the area of the cropped decoded pictures and the term "with horizontal overscan" refers to display processes in which some parts near the left and/or right border of the cropped decoded pictures are not visible in the display area. As an example, the entry "720x576 4:3 frame with horizontal overscan" for aspect_ratio_idc equal to 2 refers to having an area of 704x576 luma samples (which has an aspect ratio of 4:3) of the cropped decoded frame (720x576 luma samples) that is visible in the display area.Where's that quote from? I ask because it's clearly wrong. The 704 vs 720 difference has nothing to do with overscan. That casts doubt on the authority of the rest of it, though I happen to think the rest is correct ;)

In other words, 12:11, 16:11, 40:33 and 10:11 all assume a cropping rectangle of the clean aperture only (or "active picture" or whatever you want to call it... 704x480 for NTSC, 704x576 for PAL).I've only seen "Clean Aperture" officially defined for HD, but it's smaller than active picture - it's active picture minus the edges that might have conversion artefacts (ringing etc) - SMPTE 274M defines it as 1888x1062. FWIW, as you might expect, the concept of clean aperture is widely ignored for HD - people expect the whole HD picture to be usable.

Active picture is the part of the signal that contains, well, picture! It could be less than 704 pixels. It could (in theory) stretch outside the 720 too.

Cheers,
David.

[2Bdecided]

SAR is used to obtain a usable image using the information actually stored. For instance, valid frame sizes for DVD MPEG-2 are 352x, 704x and 720x576 (for PAL). That means the actual PAL image of a single scanline was compressed to be stored on 352, 704 or 720 pixels. How many pixels has a PAL scanline? Well, none. How many samples has 1 second of music? Still none. Based on spectral analysis, frequency response of the tape based systems and using technical common sense, it was established, but this only after digitalisation came into the video world, that it makes sense to have 702 samples on a PAL scanline, and 711 on an NTSC scanline. Still no 352, 704 nor 720, but 701(some decimals here) and 711(some decimals here too). How on hell did those values appeared?
Well, any digitizer is based on binary logic, like the PC, and since 8 and 16 were already in use in computers as well as in micro electronics, it made sense to the standardizing bodies to accept those values. 712 (the most close 8multiple to 711) was not chosen, instead 704 and 720, for the same reason why 44kHz1 was chosen for CD audio. And 704 was used to digitize analog PAL signals (close to the 702 samples).
Why 352? Because it's 704/2 and Philips thought that this is the theoretically resolution of the VHS system (corrected with the kell factor). JVC took this info in the NTSC world.
A perfect playing device needs nothing more than the storage frame size and the DAR to output a perfect PAL/SECAM signal. Because it simply need to enlarge the horizontal signal (based on the line length in storage pixels) to 711/702 samples. It's exactly the same principle as used in stretching/shrinking the audio from one standard to the other (PAL <-> NTSC). And, like in music, when one senses the wrong pitch, one can sense the wrong DAR.
The signal travels the wire and reaches a display device. What does the device do? Take the signal and stretches it to fit its native resolution. And what if the image be distorted? Then the is an incompatibility between the PAR of the source and the PAR of the display (provided the DAR is the same for both, ie 4:3 signal, 4:3 display or 16:9 source, 16:9 display). Then the device takes the signal, corrects it with PAR (display PAR), then fits it in the native resolution. It should be a perfect fit, if the PAR was correctly calculated. Is the signal in another DAR? Then the DAR is transported along (WS signalling) or the correction is done internally in the playing device. On top of this, and to partially correct some issues, came SDE, usually called Pan&Scan, which takes only one portion of the stored frame to display (logical matting).I think you're really confused!

First there was analogue video.
It was digitised at a sample rate above Nyquist.
The sample rate was chosen to work equally well for composite PAL and composite NTSC. Also component PAL and component NTSC. It had to be a multiple of 1.5MHz. IIRC the full explanation is in the EBU tech article on the 20th anniversay of Rec.601 if you want to reach it.
The part to "keep" (the active line length - the actual picture!) was chosen so it could be the same length for both formats.

Normal DVD players don't care about PAR or DAR or SAR or whatever when it comes to horizontal resolution - they take the samples, and push them through their DAC at 13.5MHz (or oversampled). They don't care which ones are active.
If you tell it you have a 16x9 TV, it takes the DAR and uses it to set the WSS flag.
If you tell it you have a 4x3 TV, it takes the DAR and uses it to vertically squash the content (or not).
Yet the DAC always runs at 13.5MHz.

The number of active pixels comes from the original analogue video standards, and the chosen sample rate for digitisation.

They didn't pick the number of active pixels they wanted first, and then figure out a sample rate to match.

Cheers,
David.

[Brother John]

@2Bdecided
Thx for the link. Might be a good start for some digging and thinking on a rainy Sunday. ;)

Where's that quote from? I ask because it's clearly wrong.
That would be the H.264 specs. In the ITU document version from 03/2010 it’s note 1 on page 374, where they describe the aspect ratio fields in the video stream.

[Ghitulescu]

I think you're really confused!

First there was analogue video.
It was digitised at a sample rate above Nyquist.
The sample rate was chosen to work equally well for composite PAL and composite NTSC. Also component PAL and component NTSC. It had to be a multiple of 1.5MHz. IIRC the full explanation is in the EBU tech article on the 20th anniversay of Rec.601 if you want to reach it.
The part to "keep" (the active line length - the actual picture!) was chosen so it could be the same length for both formats.

Normal DVD players don't care about PAR or DAR or SAR or whatever when it comes to horizontal resolution - they take the samples, and push them through their DAC at 13.5MHz (or oversampled). They don't care which ones are active.
If you tell it you have a 16x9 TV, it takes the DAR and uses it to set the WSS flag.
If you tell it you have a 4x3 TV, it takes the DAR and uses it to vertically squash the content (or not).
Yet the DAC always runs at 13.5MHz.

The number of active pixels comes from the original analogue video standards, and the chosen sample rate for digitisation.

They didn't pick the number of active pixels they wanted first, and then figure out a sample rate to match.

Cheers,
David.

I'm not confused at all. This is exactly what I said. But I started with the DVD first, because this was the topic, then I said why it was chosen this way.

Sorry if anyone else misunderstood my arguments. But the DVD players do care about the DAR (not the very old ones), because they have to signal the TV, Hey this is a 16:9 video, using the WS[S] flag.

Short comment: digitizing above Nyquist. This implies that you expect a value, to be able to double it :). This value was obtained using the engineering common sense, the electronic spot was a sort of round, so the "pixel" aspect ratio should have been close to 1. So why NTSC pixels are long while the PAL are wide? Because the sampling rate was identical and NTSC had less scanlines than PAL.

[cacepi]

Where's that quote from? I ask because it's clearly wrong. The 704 vs 720 difference has nothing to do with overscan. That casts doubt on the authority of the rest of it, though I happen to think the rest is correct ;)
In the H.264 spec, "overscan" means "anything outside the cropping rectangle." It doesn't refer to display overscan.

I've only seen "Clean Aperture" officially defined for HD, but it's smaller than active picture.
Hence the "whatever you want to call it" and dimensions for NTSC and PAL in my post.

But to properly answer, it's my Quicktime bias; all uncompressed video in Quicktime has a clean aperture, HD or not.

[yetanotherid]

I guess the fact that none I've my questions in post #74 were answered, it means none of the following posts directly apply to the original topic?

[2Bdecided]

Short comment: digitizing above Nyquist. This implies that you expect a value, to be able to double it :). This value was obtained using the engineering common sense, the electronic spot was a sort of round, so the "pixel" aspect ratio should have been close to 1.I'm not trying to be an arse (honest!) but that's not really right either.

The original analogue black-and-white standards tried to define a bandwidth which gave equal vertical and horizontal resolution. System A was the first with interlacing, and arguably allocated the wrong bandwidth because the effects of interlacing on vertical resolution weren't fully appreciated. All the subsequent standards pretty much agree on the bandwidth needed (there's are only small ~1MHz difference in luma bandwidth, for a given number of lines, the world over). (Ignoring 819-line broadcasts!).

When digital sampling came along, the sample rate was chosen based on the analogue bandwidths - which had been chose decades before. It had nothing to do with getting "close" to square pixels or round spots.

Since all the signals at the time were interlaced, having exactly square pixels wouldn't have given equal horizontal and vertical resolution (in the strict sense of the word) anyway!

So why NTSC pixels are long while the PAL are wide? Because the sampling rate was identical and NTSC had less scanlines than PAL.Yes, can't argue with that ;) Except for 16x9 :)

Cheers,
David.

[2Bdecided]

In the H.264 spec, "overscan" means "anything outside the cropping rectangle." It doesn't refer to display overscan.Wow - they had great fun giving widely used old words brand new (and contradictory!) meanings in that spec, didn't they?

Even so, the idea that 704x576 and 704x480 are the pixels that map to the correct standard DAR is a very fine one which doesn't break the old ITU standards at all (well, by less than a pixel, so who cares?). Better than the whole 720/704 confusion that the world adopted in practice.

Cheers,
David.

[2Bdecided]

I'm actually interested to know, because I'd like to know where I went wrong when encoding a DVD of an old TV series recently. In reference to the active picture area, the were sections within a single episode which required virtually no cropping, some where I needed to crop 20 or more pixels from one side and only a few from another, and some where I had to crop nearly 30 pixels from each side. So I cropped by an amount which removed the non picture area from a whole episode, picked the resizing method which seemed correct (non ITU) and encoded. What else should I have done?It sounds like the different cameras weren't set up very well! What's common over here is that the length of the active picture is correct (52us, 702 pixels), but it's location WRT horizontal sync shifts around a little from camera to camera. It almost always falls entirely within the 720 capture window (assuming that's placed correctly - without access to the analogue video signal and a video scope to start measuring things WRT to the analogue horizontal sync pulse, it's not possible to know for sure!)

Such cameras really should be ITU compliant (actually ITU-R BT.470 or SMPTE 170M compliant, digitised in a ITU-R Rec. BT.601 compliant way - I think ITU compliant will do for shorthand!). Given what sounds like very poor engineering maintenance, maybe those had drifted way off. Fixing it is like a video restoration task - way beyond a simple "what is the correct PAR?".

Like you, I'd be tempted to crop off all the black - but then I'd be left with some totally non-standard size, and I don't like that.

And even if I'd left the whole thing on the DVD because of a phobia of re-encoding to play the video on another device, if there were different resizing methods used in sections of the DVD, does my dragging an old CRT TV out of the shed to display them somehow fix them?No, of course not. If the PAR changes from camera to camera, then that DVD is wrong because the original production was wrong, because of shoddy engineering standards. Nothing will automatically fix it now.

However, I think it's more likely that the PAR is consistent between cameras, but the blanking is inconsistent. You'd have to find someone with intimate knowledge of analogue cameras 20 years ago to be sure though.

There's a more general question about what to do with crud that would be lost in the overscan of a CRT, but is clearly visible on a PC. Crop, blank, or leave? It's up to you - they're your encodes.

Cheers,
David.

[Ghitulescu]

I'm not trying to be an arse (honest!) but that's not really right either.

The original analogue black-and-white standards tried to define a bandwidth which gave equal vertical and horizontal resolution. System A was the first with interlacing, and arguably allocated the wrong bandwidth because the effects of interlacing on vertical resolution weren't fully appreciated. All the subsequent standards pretty much agree on the bandwidth needed (there's are only small ~1MHz difference in luma bandwidth, for a given number of lines, the world over). (Ignoring 819-line broadcasts!).

When digital sampling came along, the sample rate was chosen based on the analogue bandwidths - which had been chose decades before. It had nothing to do with getting "close" to square pixels or round spots.

Since all the signals at the time were interlaced, having exactly square pixels wouldn't have given equal horizontal and vertical resolution (in the strict sense of the word) anyway!

You're not an arse :) Your arguments and info are really sound and documented, unlike other people that are happy to cite wiki only. Not that wiki is wrong, but it may be.

But the need for equal H and V resolutions was required by the scanning spot (and the reproduction spot). VHS and various other sources do not have equal resolutions (optical, pixels, samples, you name it) yet few people can see the difference. Was not even in the first mechanical TV systems, it is not in some HDTV flavours (like HDV).

This way resulted the bandwidth, not vice-versa (ie the bandwidth generated the resolution and the PAR and the DAR). In the "ancient" times of the TV, the bandwidth was so limited, that interlacing was invented to keep it at the minimum while still preserving the PAR/DAR/timings/etc. Should it be the bandwidth the "first born" and all other parameters made dependent thereon, it would have been no problem to let the scanning spot sweep longer the scanlines for wider "pixels" (slower changes, lower frequencies, more distant sampling intervals, you name it), like is the case with the VHS/Video8. Nobody would have noticed it, like with the VHS case.

[mpucoder]

WRT to post 74 - the info about the true geometry of NTSC was meant more for informative purposes. If someone is going to argue about the real PAR then start with the real geometry (the AR is well known).

I agree with 2Bdecided about the DVD in question - badly made. There are other ways the aperture could shift besides the cameras, though. Analog cameras not only need their timing properly adjusted, but, in order to be transitioned (with what used to be called an SEG, but more and more just called a switcher) the signals must be synchronized to each other. There are 2 ways to do that, either by genlocking the cameras to a master clock, or using TBC/framesync after the camera. Getting the timing right is very tricky, and subject to change day to day or, in the case of genlocked cameras, simply moving a camera can change its timing (the capacitance of the cable can be affected by bending it). If this were the case the shifts would occur at camera changes and you would be able to determine which camera was off.
If, on the other hand, the shifts are unrelated to which camera and don't change from shot to shot, but from sections that are seamingly random, the problem lies elsewhere. My best guess would be different equipment used to telecine different segments, possibly with some processing - every analog processor also has to account for its propagation delay. Some equipment introduces very small delays that go uncorrected to save cost since the delay is barely noticable.
Such are the headaches of analog video (there are even worse, such as color shifts in live remote broadcasts caused by environmental factors, that's why there was a vectorscope in the receiver room)

For anyone trying to view the full sized images in the first post - I had to remove the links to imageshack after one of their advertisers attempted to lure me into downloading a fake virus scanner (av8scan scam)

[mpucoder]

I had another thought - different parts of the production could have been shot on different days, or even in different studios, which could account for large sections having different apertures.

[yetanotherid]

I had another thought - different parts of the production could have been shot on different days, or even in different studios, which could account for large sections having different apertures.

I've no doubt that was the case. The opening credits would have required a particular amount of cropping, the stuff shot live in the studio generally another, the exterior shots required a different amount of cropping and not of of them by the same amount, and when the amount cropped was similar sometimes the picture was placed to the left or right rather than in the centre etc....
Those DVDs were of course an extreme example, but it's hardly something which is uncommon. In the case of those DVDs I did crop off all the crud, picked a mod16 width after cropping (an average for all episodes) and resized them all to the same width. As they were 4:3 content I also cropped enough from the top and bottom to end up with a perfect 4:3 display aspect ratio. To me that was best way to transfer the video from DVD-land and end up with nice, clean copies.

What I'm still not sure about though, is the OP started this thread to try to work out the best way to resize and crop his DVDs when encoding, but so far none of the bickering over old analogue standards seems to have any direct relevance to the original topic. While I guess it's nice to discuss it (even though hypocritically one of the participants told me earlier I should start a new thread if I wanted to have a PAR discussion) how does any of it have any real practicality when it comes to deciding how to make an encode of a DVD?

[2Bdecided]

What I'm still not sure about though, is the OP started this thread to try to work out the best way to resize and crop his DVDs when encoding, but so far none of the bickering over old analogue standards seems to have any direct relevance to the original topic. While I guess it's nice to discuss it (even though hypocritically one of the participants told me earlier I should start a new thread if I wanted to have a PAR discussion) how does any of it have any real practicality when it comes to deciding how to make an encode of a DVD?Because if it was properly made in the first place you'd know what the PAR was! ;)

Cheers,
David.

[mpucoder]

I see two sides to this, the perfectionist, and the practical. Practical works for me.
To be practical, pick a method that looks good to you, your brain will adjust to any anomolies. You may have to correct some really bad DVDs, but hopefully they are rare.
To the perfectionists - you can spend a lifetime trying to get it perfect, and then someone like me will point out a flaw. One big one to consider is viewing angle - to be perfect one must view the image dead center both vertically and horizontally. This doesn't happen in the cinema for anyone (they would block the projection) yet no one complains (well, maybe the people in the wall aisle do, or the front row). Sitting off-center introduces perspective that creates a trapezoid (trapezium to the British) image, yet the brain compensates.

[yetanotherid]

Because if it was properly made in the first place you'd know what the PAR was! ;)

Which logically means it's only relevant if there's a way to determine whether the DVD was properly made?

Okay, so I just grabbed a PAL DVD. It's 16:9, no black bars, but needs a row of pixels top and bottom removed (half lines of "crud"). Even though it probably doesn't need cropping at all at the sides, I'd crop a couple of pixels from both to make the sides nice and sharp. Can I determine the correct PAR from any of that?

[Sharc]

Which logically means it's only relevant if there's a way to determine whether the DVD was properly made?

Okay, so I just grabbed a PAL DVD. It's 16:9, no black bars, but needs a row of pixels top and bottom removed (half lines of "crud"). Even though it probably doesn't need cropping at all at the sides, I'd crop a couple of pixels from both to make the sides nice and sharp. Can I determine the correct PAR from any of that?
Not sure if I understood your question fully, but by just cropping something off you don't change the PAR (i.e. Pixel Aspect Ratio). The PAR (Pixel Aspect Ratio) is only changed with resizing. When one applies cropping plus resizing one can calculate the "New PAR" like:
New_PAR = Original_PAR x (resized_height x cropped_width) : (cropped_height x resized_width)
Unfortunately only the studio could tell you what "Original PAR" they applied when they encoded the DVD. Otherwise you can only guess using the circles/squares method, or you may want to start from the Movie Aspect Ratio (like 2.35:1) which you find on the DVD cover or from a movie database, crop the black borders (if any) exactly off and try to calculate (spreadsheet) which of the standard PARs (generic, Mpeg-4, ITU) gets closest to the active width/active height ratio.... Good luck.

[Dogway]

Unfortunately only the studio could tell you what "Original PAR" they applied when they encoded the DVD. Otherwise you can only guess using the circles/squares method, or you may want to start from the Movie Aspect Ratio (like 2.35:1) which you find on the DVD cover or from a movie database, cropp the black borders (if any) exactly off and try to calculate (spreadsheet) which of the standard PARs (generic, Mpeg-4, ITU) gets closest to the active width/active height ratio....

Would it be safe to assume they didn't crop out any of the original active picture and I only need to crop the blanking and apply the DAR informed on the Movie Database (or any film generic AR, 1.85,2.35,1.77...)
This doesn't seem a very orthodox procedure as for a 1:1 DVD conversion, but maybe for a good workaround DVD restoration(?)

[Sharc]

Would it be safe to assume they didn't crop out any of the original active picture and just crop the blanking and apply the DAR informed on the Movie Database (or any film generic AR, 1.85,2.35,1.77...)

No, I wouldn't take it as granted. We don't know how they cropped. I just mentioned the Movie Aspect Ratio as one method how to come to a conclusion on the "most likely" applied PAR. At least I had cases where it became reasonably obvious whether ITU or Generic has been applied. The method can also help to confirm the conclusion from the "circles" tests. The errors are small anyway, so the problem is luckily a bit academic.

[SeeMoreDigital]

To the perfectionists - you can spend a lifetime trying to get it perfect, and then someone like me will point out a flaw.Here's another option for the perfectionists to pursue.

Find some still images from the "square pixel" Blu-ray version of the movie to work-out the movies aspect ratio. And use them to determine the level of aspect ratio signalling required for your anamorphic encodes.

[Dogway]

If only I had any 1080 MGM lion screenshot... :rolleyes:

[yetanotherid]

Not sure if I understood your question fully, but by just cropping something off you don't change the PAR (i.e. Pixel Aspect Ratio).

Yeah.... my question/example though related to the earlier statement by another poster....
"because if it was properly made in the first place you'd know what the PAR was"

I'm trying to establish if there's really any way to know whether a DVD was in fact made properly. i.e. If there's "x" amount of active picture area then PAR "y" must have been used. That sort of thing.

[Ghitulescu]

I'm trying to establish if there's really any way to know whether a DVD was in fact made properly. i.e. If there's "x" amount of active picture area then PAR "y" must have been used. That sort of thing.

Yes, phone the mastering engineer and ask him this question. He'll be glad to tell you what source has been used and how this was digitzed.

[netmask]

Of course there is another variable to consider just to muddy the waters a tad..... a bit off topic but a possibility :)

most feature movies were shot using celluloid ie optical film and generally they only use one camera. Same with modern productions using digital camera's - just one camera and many set ups. There are exceptions with block buster movie's to cover one off effects but in the main unlike TV production the philosophy of using one camera is to maintain artistic integrity and correct lighting from one point of view. The moment you have 2 camera's shooting simultaneously the lighting has to be compromised and also makes it difficult for folk like me, the sound recordist to move the microphone around the action without casting multiple shadows. So returning more to the thread you need to establish "how" the movie was shot before worrying too much about aspect ratios. Also look up the work of Kuberick and what he did to aspect ratio right at the source putting masques in the camera and fiddling with the final negative...

[netmask]

http://kubrickfilms.warnerbros.com/faq/general_faq.html

# Why are some of Kubrick’s films not available "letterboxed" on home video?

Kubrick had total control over the aspect ratios (ratio of the width of a film image to its height) of his films, in their theatrical release and on home video. He liked to experiment, and he liked to question conventions regarding aspect ratios, so it’s no surprise that there is no real consistency regarding the home video versions of his films.

Spartacus and 2001: A Space Odyssey were the only films he shot using a "widescreen" format (Super Technirama on Spartacus and Super Panavision on 2001), so those would be the only two really hurt by not being letterboxed (both are available on video and DVD letterboxed to approximately their proper aspect ratios).

A Clockwork Orange and Barry Lyndon were shot and released in most theaters in the matted 1.66 : 1 widescreen ratio, and The Shining, Full Metal Jacket and Eyes Wide Shut were shot open-matted (or full-frame) and framed for a theatrical release in the American standard ratio of 1.85 : 1.

However, Kubrick preferred on all these films that they be transferred to home video fullscreen (a ratio of about 1.37 : 1). Had he remained alive to see the rising popularity of widescreen and high-definition TVs, he may have eventually changed his mind about these films.
# What is the definition of "letterboxed"?

"Letterboxed" is the term commonly used to describe when a feature film is shown

in its original aspect ratio on TV (meaning that there are black bars on

top of and below the image, to simulate a movie screen).

"Matting" can also be used, but is more commonly a term used in connection with the actual filming process, i.e. "Kubrick normally matted his films for a 1.66 : 1 aspect ratio."

It means putting an actual hard mat inside the camera to cut out part of the image. When referring to home video, "letterboxing" is the more common term.

[Ghitulescu]

Many films were shot in Academy, yet released in the matted versions (for both technical and marketing reasons). Since the DVD employs non-square pixels and there are several standards and recomandations that it has to obey (for MPEG-2, DVD, NTSC/PAL) this issue is difficult to be solved otherway than by trial-and-error. The BD solved at least the geometric aspects.

[yetanotherid]

Yes, phone the mastering engineer and ask him this question. He'll be glad to tell you what source has been used and how this was digitzed.

So you're saying none of your off-topic attempts to share your intimate knowledge of the history of the analogue pixel had any relevance to the discussion of determining DVD PAR and which resizing method to choose when converting a DVD?
I thought not. I can usually pick a dinosaur when I see one.

[Ghitulescu]

Converting is a notion that needs 2 items to become functional: a starting point and a destination. Your cry for help won't get any answer, as the destination is unknown.
I said before and in other occasions why I am against converting DVDs into new codecs, in short, apart from a sligth size reduction (irrelevant today), only problems (if one wants to do a perfect job).

BTW: one of the top 10 mankillers is a dinosaur. Another toptenner is a close relative. Beware! :) :p

[yetanotherid]

Converting is a notion that needs 2 items to become functional: a starting point and a destination. Your cry for help won't get any answer, as the destination is unknown.

So why'd you spend so much time pontificating about DVD PAR in this thread if it's irrelevant.?

I said before and in other occasions why I am against converting DVDs into new codecs, in short, apart from a sligth size reduction (irrelevant today), only problems (if one wants to do a perfect job).

Aside from PAR, which problems are they?
A "slight" as you put it.... if you can consider a half to 3/4 reduction to be "slight".... is still quite relevant unless you want to be lugging discs or transferring 12GB of vob files to a portable device to watch a couple of movies.
And I can think of enough benefits to outweigh a non-existent reason for not doing so. If I encode a DVD anamorphically and do so pixel for pixel, where's the problem? The display aspect ratio of an MKV isn't written in stone and I can change it at any time. I can make one encode using the non-ITU resize method for me, then run it through MKVToolNix and change the DAR for you so you can watch an ITU resized version while you reminisce over your old CRT TV. And if later on I decide I want it to be perfect and resize different sections different ways, I've still got the DVD source from which to make a new original encode.
So where's the reason for not doing so? I'm still not seeing it.

[Ghitulescu]

Sorry, forget an old fool. Of course you're right and I was wrong. Please use your infinite wisdom and enlighten the original poster with some bits of knowledge.

[yetanotherid]

Sorry, forget an old fool. Of course you're right and I was wrong. Please use your infinite wisdom and enlighten the original poster with some bits of knowledge.

Okay. Just the relevant bits, or will you be returning?

[Sharc]

Would it be safe to assume they didn't crop out any of the original active picture and I only need to crop the blanking and apply the DAR informed on the Movie Database (or any film generic AR, 1.85,2.35,1.77...)
This doesn't seem a very orthodox procedure as for a 1:1 DVD conversion, but maybe for a good workaround DVD restoration(?)
I downloaded your sample .m2v. Applying my method and ASSUMING a Movie Aspect Ratio of 1.85:1 the most likely PAR I found is 40:33 (i.e. mpeg-4 for NTSC 16:9 DVD). It's almost within 1 pixel accuracy which may be attributed to the half line scan issue explained by 2bdecided (thanks!), or due to some rounding or pixel ruler errors.
I don't know the title of the movie, so I took 1.85:1 as my initial assumption and everything seems to fit pretty nicely....

[Dogway]

You mean this?:

(64/54)*((716/720)/(468/480))=1.2088
Film is said to be 16:9 in imdb...

[manono]

Film is said to be 16:9 in imdb...
How about a link? Until very recently there were no movies made meant to be shown at 1.78:1, although DVDs do sometimes change the theatrical aspect ratio. For me 16:9 is a DAR and not a movie aspect ratio.

[Dogway]

IMDB (http://amazon.imdb.com/title/tt0089052/)
I read it here or in amazon, but I swear I saw it, they may have changed it.

[Sharc]

You mean this?:

(64/54)*((716/720)/(468/480))=1.2088
Film is said to be 16:9 in imdb...
No, I mean:
Your source DAR is 16:9, format is NTSC, 720x480 for full DVD picture.
I don't believe the movie aspect ratio is 16:9 because letterboxing (borders) have been applied. So looking at the size of the borders my guessing was for 1.85:1 for the movie aspect ratio.

The active height of your picture is 468 pixels.
Now the studio had the choice between applying the Generic 64:54, mpeg-4 40:33 or ITU 5760:4739 PAR.
What is the anamorphic active width when assuming the 40:33 PAR?
=> 468*1.85*33/40=714.3
So one has to add total 6 pixels borders (e.g. 4 left, 2 right) for 720 DVD compliance. This is very close to what has been done to your original picture. Hence I concluded on a PAR of 40:33.
You can do the same calculation for the other PARs and you will find that they deviate more.

As I said, this is my best guess.

[Ghitulescu]

Did ever occured to anyone of you that the film might be side cropped before reaching the DVD? Soemtimes is done to mask the side irregularities or defects.

[manono]

Did ever occured to anyone of you that the film might be side cropped before reaching the DVD? Soemtimes is done to mask the side irregularities or defects.
Hehe, I suspect it's 1.33:1 (cropped on top and bottom) as IMDB says it was both shot and displayed at 35mm (although I suppose it could have been matted during display), and the pics I saw in reviews seem to show it to be 1.33:1 (or maybe Academy Ratio (1.37:1)).

Did you cap this film, Dogway, as there doesn't seem to be an official DVD release? Too bad, as I'd like to see it. It looks like a fine film.

Edit: I take back that last paragraph as Amazon.com lists a DVD of it. But with no mention of the aspect ratio or of the DAR, which is unusual for them.

Edit again: But one of the user reviews at Amazon.com says it's a 16:9 DVD.

[Dogway]

I don't know if I can call it official, its sold by amazon in a DVD-R. I think it was originally widescreen as noted in the amazon trailer

[Sharc]

Hehe, I suspect it's 1.33:1 (cropped on top and bottom) as IMDB says it was both shot and displayed at 35mm (although I suppose it could have been matted during display), and the pics I saw in reviews seem to show it to be 1.33:1 (or maybe Academy Ratio (1.37:1)).

Did you cap this film, Dogway, as there doesn't seem to be an official DVD release? Too bad, as I'd like to see it. It looks like a fine film.

Edit: I take back that last paragraph as Amazon.com lists a DVD of it. But with no mention of the aspect ratio or of the DAR, which is unusual for them.

Edit again: But one of the user reviews at Amazon.com says it's a 16:9 DVD.
1:33 or Academy was my first thought as well, but given the sample clip of Dogway I assumed a 16:9 DAR DVD as source.

[yetanotherid]

Did ever occured to anyone of you that the film might be side cropped before reaching the DVD? Soemtimes is done to mask the side irregularities or defects.

Yes. :)