PAL DVD - How to make square pixels

[TheLastOfThem]

The image on a DVD is actually sampled at 720 or 704 and not just upscaled from 640.
640x480 is not a common source for professional productions.

However, I agree, you do not necessarily lose any visible resolution by resizing down to 640. This is not related to the original source being 640, it's simply because the image is blurry enough.

If the video is really detailed and not low-pass filtered you will lose visible resolution by resizing down to 640.

Also the resizing in itself is destructive, as jagabo pointed out.

When sampled do you mean the picture is actually 720 or 704? Because then why would it be stretched if it wasn't a different size?

[manono]

When sampled do you mean the picture is actually 720 or 704?

Yes, that's what he means. You do understand, don't you, that DVDs usually use sources of much higher resolution to begin with? So, why would it be difficult to digitize and then resize a 1.33:1 film source or a 1440x1080 digital source to 720x480?

Because then why would it be stretched if it wasn't a different size?

All DVDs are, by definition, stored at a 'stretched' resolution. And that's because DVDs have, by definition, DAR's of either 4:3 or 16:9. If you want 1:1 (non-stretched, non-anamorphic), you can encode an MPG for that, but not DVD video.

[jagabo]

Why would taking 720x480 and resizing to 640x480 nonsquare "lose 11%" of resolution? It's not like the image is ACTUALLY 720 even if the DVD PAR stretches it.

Yes, if the source was VHS tape with only ~350 lines of resolution, or even studio video tape with ~500 lines of resolution, downsizing from 720 to 640 may not noticeably degrade the image. But some DVDs are made from source that have much higher resolution. A 1.37:1 movie shot of film might be digitized at ~4000x3000 resolution and downscaled for DVD.

[TheLastOfThem]

DVDs usually use sources of higher resolution..this I was unaware. But at the same time - how does one know it's using a higher sampled source? Because at the end of the day - the display size ends up being 640x480 according to DGIndex for the DVD I have. Display dimensions: 640x480. So how can one say you'd lose 11% if you go to square pixels?

Basically I'm wondering how does one know the image is actually 720x540 as opposed to 640x480 in a DVD? Jagobo says you'd lose 11% but how is that explained?

[jagabo]

how does one know it's using a higher sampled source?

Look at it.

Because at the end of the day - the display size ends up being 640x480

Only if you view it in a 640x480 window or display. IN ALL OTHER CASES THE VIDEO WILL BE SCALED DIRECTLY FROM 720X480 TO THE TARGET DISPLAY SIZE.

[TheLastOfThem]

how does one know it's using a higher sampled source?

Look at it.

Because at the end of the day - the display size ends up being 640x480

Only if you view it in a 640x480 window or display. IN ALL OTHER CASES THE VIDEO WILL BE SCALED DIRECTLY FROM 720X480 TO THE TARGET DISPLAY SIZE.

Can you please explain how you got 11% resolution loss going from a 720x480 frame to a 640x480 nonsquare? I didn't understand that. I am viewing the DVD on a PC and it shows as a 640x480 square on VLC.

[jagabo]

640 / 720 = 0.88... about 11 percent reduction.

[TheLastOfThem]

640 / 720 = 0.88... about 11 percent reduction.

That's ASSUMING the source is actually filling up the width of the DVD frame though....which it clearly isn't. It's outputting a 640x480 square on my PC.

[manono]

Can you please explain how you got 11% resolution loss going from a 720x480 frame to a 640x480 nonsquare? I didn't understand that.

640/720=0.88888...=11+% loss of resolution.

I am viewing the DVD on a PC and it shows as a 640x480 square on VLC.

Because that's how it's being resized by VLC, and that's what it tells you in its information. I play a 4:3 VOB file from a DVD using MPC-HC and it tells me the VOB is 720x480. That information is provided by MediaInfo and if you opened your VOB in MediaInfo it would tell you the same.

People are going to get a little annoyed with you if you repeat your same questions time and time again. Have you done any research at all for yourself? Here, read this from top to bottom - or at least the parts that interest you - and if you still have questions when all done, then come back and ask them:

http://www.dvddemystified.com/dvdfaq.html

[TheLastOfThem]

Can you please explain how you got 11% resolution loss going from a 720x480 frame to a 640x480 nonsquare? I didn't understand that.

640/720=0.88888...=11+% loss of resolution.

I am viewing the DVD on a PC and it shows as a 640x480 square on VLC.

Because that's how it's being resized by VLC, and that's what it tells you in its information. I watch a 4:3 DVD using MPC-HC and it tells me the VOB is 720x480. That information is provided by MediaInfo and if you opened your VOB in MediaInfo it would tell you the same.

People are going to get a little annoyed with you if you repeat your same questions time and time again. Have you done any research at all for yourself? Here, read this from top to bottom - or at least the parts that interest you - and if you still have questions when all done, then come back and ask them:

http://www.dvddemystified.com/dvdfaq.html

I'm not asking the same question. I'm asking 1 question which people are not answering. If obviously a 720x480 DVD is being RESIZED to 640x480 on the PC or say a 640x480 display...that's the AR set. That doesn't mean just because you stretch a 640x480 image master to 720x480 it's suddenly 11% better on the DVD. Even if it's sampled from 4000x3000 which would mean film....It still has to be 4:3. In which case they can't take 720 pixels width-wise from the frame. The visible area would still be 4:3....

If the AR is 4:3 then thats the frame they can shoot in. They can't squeeze a wider image onto a smaller frame (640 width with 720 pixels of the scene - maybe showing more of a tree) without using a wider angle lens...otherwise something will look worse

[LMotlow]

LOL!. Looks like you guys have another winner from videohelp's target demographic.

[_Al_]

It is NOT resized to 640x480 on the screen. It is resized to your monitor resolution or players's window.

It CALCULATES new resolution. Alghorithms have 720 pixels available and compute 1440 out of it, if you have 1920x1080 monitor and using full screen.
IF the source was 640x480 then algorithm has only 640 pixels to calculate 1440 pixels out of it. That is less than 720. So 720 is better.

Imagine you had "alien" anamorphic DVD that has 7200x480 pixel BUT 4:3 aspect ratio. Watching it on 4000x3000 monitor , big like a house. Now watch the same video with 640x480 on the very same screen, 4000x3000. That would look like crap comparing to that first one. So those 720x480 has a slight advantage.

In reality is not that a bif deal though. Real world videos are not like testing pictures. Having inderlaced DVD and deinterlacing DVD using QTGMC, then resizing gives a very good result even if ending up with 640x480.

[TheLastOfThem]

It is NOT resized to 640x480 on the screen. It is resized to your monitor resolution or players's window uses.

Alghorithms have 720 pixels available and compute 1440 out of it, if you have 1920x1080 monitor and using full screen.
IOF the source was 640x480 than algorithm has only 640 pixels to calculate 1440 pixels out of it. That is less than 720. So 720 is better.

Imagine you had "alien" anamorphic DVD that has 720x480 pixel BUT 4:3 aspect ratio. Watching it on 4000x3000 monitor , big like a house. Now watch the same video with 640x480 on the very same screen, 4000x3000. That would look like crap comparing to that first one. So those 720x480 has a slight advantage.

In reality is not that a bif deal though. Real world videos are not like testing pictures. Having inderlaced DVD and deinterlacing DVD using QTGMC, then resizing gives a very good result even if ending up with 640x480.

I know what you're saying about it resizing to the native display. I already acknowledged that. But what no one is still answering is - if the output on a PC ends up being 640x480 in VLC...then that must mean the original source WAS 640x480 does it not just squeezed in DVD form frame? Otherwise please tell me how some studios can take 4000x3000 (which consists of an entire scene) and then obviously they have to squeeze it down to 720 pixels wide and 480 in height (which is not the same AR). So there's stretching involved. It's not like they're creating more detail to say "you lose 11%" if the image is the same as a 640x480 image just bigger from the film master

[TheLastOfThem]

LOL!. Looks like you guys have another winner from videohelp's target demographic.

If you're going to be the big sarcastic lack of contribution to society that you are go do it elsewhere, please. No need to make fun of anyone confused/learning. It is called VideoHELP. If you think you're better, then please go F*** off and make a VideoExpert.com site. Reported. And I quite frankly don't care if my language is equal to being reported (which I already did to myself as well - in fairness). You're flaming and are the only one who looks seriously beyond stupid acting high and mighty on a site meant to help people and complaining about it like its a bad thing.

[_Al_]

OK, we have 4000x3000 movie source, now, imagine I make myself anamorphic video 4000 x 480 giving it aspect ratio 4:3 ! Totally possible. It would look fantastic (comparing to anamorphic 720x480 or square pixel 640x480) on UHD TV or PC monitor with VLC on full screen.

While watching that video on VLC player in resized 640x480 window, it might look very bad due to downscaling artifacts, or with combination deinterlace/downscale combo. But in real world, nowadays , you upscale all the time basically evn watching that stuff on the phone.

[TheLastOfThem]

_Al_ thank you for your continued patience with my questions.

So basically people here are saying that if you have 720x480..and you make it 640x480 theoretically even if the picture on the frame is 640x480 - you'd lose a theoretical 11% of possible scanline data from the DVD frame as opposed to just simply leaving it set with anamorphic because otherwise resizing would make it look worse?

Also not clear on your 4000 width-wise example. If we have a film master of say Seinfeld...and we take 4000 width wise - we'd obviously have to proportionately take a 3000 height wise sample. We cannot possibly just take 480 pixels and have 4000 as the width with missing height information?

[jagabo]

if the output on a PC ends up being 640x480 in VLC...then that must mean the original source WAS 640x480 does it not

No. The image on the DVD is 720x480. The 4000x3000 image was downscaled "anamorphically" to 720x480. 640x480 never existed anywhere.

[TheLastOfThem]

if the output on a PC ends up being 640x480 in VLC...then that must mean the original source WAS 640x480 does it not

No. The image on the DVD is 720x480. The 4000x3000 image was downscaled "anamorphically" to 720x480. 640x480 never existed anywhere.

Even if you anamorphically downsize to 720 x 480 - you are still using an image which is 4:3. Stretching it out onto a 720 wide frame should not theoretically make it any better as anything you do can only display in multiples of 4:3 anyways (640x480 being one of them) - assuming it's on a PC screen where it doesn't force stretch to fit your screen.

I took a 4000x3000 image - shrinked and stretched down to 720x480. It's still the SAME image. Similar to if a studio got this image http://www.socwall.com/images/wallpapers/40025-4000x3000.jpg

and shrunk it down - its still the same image being altered. why would it being housed in a 720x480 block be better than being housed in a 640x480 block at the end of the day? You're still using the original dimensions of 4000x3000 of the picture. Not 4720x3000.

[jagabo]

why would it being housed in a 720x480 block be better than being housed in a 640x480 block at the end of the day?

Because 720 pixels hold 11 percent more information than 640. Using your logic: resize the image to 16x12. That's still 4:3. How good is the picture then? You are fundamentally misunderstanding the relationship between aspect ratio and frame size. Any frame size can represent any aspect ratio. The frame size limits the amount of detail the image can contain. The aspect ratio is just the shape of the final displayed picture.

[manono]

Not 4720x3000.

I think you mean 4500x3000.

Okay, have it your way. Say you resize that 4000x3000 image first to 4500x3000 before then resizing down to 720x480. You don't think that 720x480 image will have more detail than a 640x480 image resized from it?

And what if you performed both operations at the same time - stretched it to 1.5:1 at the same time you downsized to 720x480 (jagabo's 'downscaled "anamorphically" to 720x480')? You don't think that 720x480 image will have more detail than a 640x480 image resized from it?

Edit: Too late

[TheLastOfThem]

why would it being housed in a 720x480 block be better than being housed in a 640x480 block at the end of the day?

Because 720 pixels hold 11 percent more information than 640. Using your logic: resize the image to 16x12. That's still 4:3. How good is the picture then? You are fundamentally misunderstanding the relationship between aspect ratio and frame size. Any frame size can represent any aspect ratio. The frame size limits the amount of detail the image can contain. The aspect ratio is just the shape of the final displayed picture.

720 pixels hold 11 percent more information even if the image being stretched to fit that 720 pixel frame size is still sourced from say a 4:3 AR image of 4000x3000? It must still display on a PC that doesn't force-stretch at 4:3...which would be 640x480. That 720 pixels cannot possibly mean you have 500 MORE discrete resolution width-wise of the 4000x3000 image.. it's still 4000x3000.

[TheLastOfThem]

Not 4720x3000.

I think you mean 4500x3000.

Okay, have it your way. Say you resize that 4000x3000 image first to 4500x3000 before then resizing down to 720x480. You don't think that 720x480 image will have more detail than a 640x480 image resized from it?

Yes 4500x3000 sorry. But the studios won't make it 4500x3000. They'd still put a 4000x3000 image on the 720x480 block/frame. It doesn't give the image more data.....the end result with AR on a 720x480 will still show as 640x480 on a PC

[_Al_]

Also not clear on your 4000 width-wise example. If we have a film master of say Seinfeld...and we take 4000 width wise - we'd obviously have to proportionately take a 3000 height wise sample. We cannot possibly just take 480 pixels and have 4000 as the width with missing height information?

Yes , we can, this is anamorphic video. This is the whole point. DVD's are like that. With/Height does not have to be same as displayed aspect ratio. Imagine anamorphic video with rectangle pixels.

Also think of anamorphic resolution only to exist, to be created for storing purpose only. They are never proportionally shown with that width/height ratio. Correct proportions are always calculated while watching it on screen.

[TheLastOfThem]

Take a look at this image.

It is 4000x3000

http://www.socwall.com/images/wallpapers/40025-4000x3000.jpg

I fit it into 720x480 like movie studios.

https://snag.gy/AnwjX3.jpg

I then put it on DVD like this -

https://snag.gy/WdIB56.jpg

This image when done anamorphically - will be 640x480 on display.

So why wouldn't a 640x480 image from this picture look the same? It would just end up looking like this

https://snag.gy/RTfSNX.jpg

Looks the same ....because it's the same image just stretched on 720x480

[TheLastOfThem]

Also not clear on your 4000 width-wise example. If we have a film master of say Seinfeld...and we take 4000 width wise - we'd obviously have to proportionately take a 3000 height wise sample. We cannot possibly just take 480 pixels and have 4000 as the width with missing height information?

Yes , we can, this is anamorphic video. This is the whole point. DVD's are like that. With/Height does not have to be same as displayed aspect ratio. Imagine anamorphic video with rectangle pixels.

Also think of anamorphis resolution as existing merely for storing purpose. They are never proportionally shown with that stored ratio.

That's a very stretched image though....

https://snag.gy/SsHx29.jpg

[TheLastOfThem]

I apologize to anyone for my incompetence but...the way I'm looking at it is the original source is 4:3. That's Aspect Ratio. Then they put it on a 720x480 square....which then continues to stretch the image. This image gets unstretched and is shown as 640x480. 720x480 stretching out what was already a 4:3 square from say 4000x3000 does not mean it was from a 4500x3000 image....how on earth can it possibly have more information when the image is exactly the same on that frame? (Basically there are NO extra pixels on that bigger frame). Just an image which was STRETCHED. So why can't we just unstretch that image into square pixels and make it 640x480 1:1?

Where can "extra information" be coming from?

[_Al_]

That's a very stretched image though....

Nothing is stretched. That 4000x480 is only for storing purposes. While watching that video, VLC player would read that storage aspect ratio which would be 480/3000 = 4/25 fraction or in decimal value 0.16 . While playing that video it would pick up that 480 and divide it with that stored aspect ratio. 480/0.16 . It would get 3000 and that would give on screen. So while thinking about anamorphic video, you must think of that. Value of that stored aspect ratio is not the same as real display aspect ratio.

So you can try it , having 4000x3000 video, resizing it to to 4000x480 and encode it with 4/25 stored aspect ratio (using x264 for example) and then give it to VLC. Both videos should be played proportionally correct, same way, sure that 4000x480 would look like crap, because it lacks resolution and VLC would need to extrapolate a lot of pixels, upscaling it, outputting it on screen but that is another subject.

Another example , you have DVD 720x480 and you want to encode it as anamorphic as well, using x264 encoder. Assume video is already progressive. You'd need to tell encoder to use aspect ratio, x264 calls it SAR, stored aspect ratio, in that case it would be 640/720=8/9. So while playing that video VLC player would get 480 and devide it with 8/9 getting 540. 720x540. Or multiplying horizontal resolution by 8/9 getting 640. Whatever needs to be done, there is active window involved, so it calculates whatever it needs to be fit on screen. That it would output on screen, perhaps not 720x540 or 640x480, always 4/3, but whatever monitor resolution or active player window you'd have, but always with correct 4/3 aspect ratio then. Even if video was stored as 720x480 which is not 4/3. That stored aspect ratio value must be always present in H.264 anamorpic video. You did not have it involved on your image sample, so all you get is a stretched image only.

While making DVD, you do not have to input that so called stored aspect ratio, it is called a bit different, someone might pick this up , but anyway, because DVD has only two, one for 4:3 video and another for 16:9 video. This is simplified a bit because DVD could be 704 not 720, it is complicated, perhaps DVD always assumes 704 and those 16pixels are just pillarboxed while viewing, heated discussions about this, ..., but just to understand , while making DVD you choose 4:3 or 16:9 reference and all is taken care of automatically. In H.264 video you'd need to specify that value as I mentioned. Or not, then it is assumed that value is 1.0 , square pixel video.

Anyway, back to that posted image. One interesting thing. Photoshop can create anamorphic project as a matter of fact, creating PSD project . At least for DV/DVD projects, as far as I know, I use it all the time (well used it), it has DV template , it is 720x480 but when you paste any object in it, it is proportionally corrected right away for DVD, so when you export 720x480 jpg to be viewed on DVD, it is proportionally correct then.

[LMotlow]

LOL!. Looks like you guys have another winner from videohelp's target demographic.

If you're going to be the big sarcastic lack of contribution to society that you are go do it elsewhere, please. No need to make fun of anyone confused/learning. It is called VideoHELP. If you think you're better, then please go F*** off and make a VideoExpert.com site. Reported. And I quite frankly don't care if my language is equal to being reported (which I already did to myself as well - in fairness). You're flaming and are the only one who looks seriously beyond stupid acting high and mighty on a site meant to help people and complaining about it like its a bad thing.

Cool, sparky. Keep at it. The clique here will have this thread going until 2020 and will love you for it. Good luck, and keep in touch with yourself. Meanwhile, you'll find out that this group is really good at flaming, so keep up that great simple-simon act and they'll go orgasmic.

[jagabo]

720 pixels hold 11 percent more information even if the image being stretched to fit that 720 pixel frame size is still sourced from say a 4:3 AR image of 4000x3000?

Yes.

It must still display on a PC that doesn't force-stretch at 4:3...which would be 640x480.

No, it does not have to be displayed at 640480 to maintain a 4:3 aspect ratio. It can be displayed at 320x240, 480x360, 960x720, 1024x764, 1280x960, 1440x1080, 2880x2160... any 4:3 size you want. At the larger frames sizes you will get 11 percent more detail from a 720x480 anamorphic frame than from a 640x480 square pixel frame.

Why are you obsessed with 640x480? 640x480 is never involved in making a DVD. It's only one possible way of displaying it.

[manono]

...stretching out what was already a 4:3 square from say 4000x3000 does not mean it was from a 4500x3000 image....how on earth can it possibly have more information when the image is exactly the same on that frame?

That's right, a 4500x3000 image made from a 4000x3000 image doesn't have more information than the original 4000x3000 image. It has a helluva lot more information than a 720x480 image made from it or made from the 4000x3000 source, and even more (11% more) than a 640x480 image made from the 720x480 image.

My suggestion is if you can't understand basic mathematics you just forget about it. By not resizing 720x480 and setting a SAR flag to tell the player to do the resizing when it plays it at 640x480 or any other 1.33:1 ratio, you avoid a resizing step, which by itself saves quality. Having said that, I resize both my DVD and tape sources to 640x480 for MP4 before then uploading them to YouTube. In addition, not all playback devices will use that aspect ratio flag to play the videos properly. If you know yours do, then you'll be slightly better off keeping them at 720x480.