PAL DVD - How to make square pixels

[TheLastOfThem]

Hi Everyone,

Is it better to retain anamorphic flag from a DVD (720x576) or make it 767x576?

Also for NTSC DVD's is 640x480 really identical to 720x480 in terms of detail ?

[usually_quiet]

Hi Everyone,

Is it better to retain anamorphic flag from a DVD (720x576) or make it 767x576?

Also for NTSC DVD's is 640x480 really identical to 720x480 in terms of detail ?

The DVD spec doesn't allow the use of square pixels. Use 720x576 for PAL and 720x480 for NTSC.

If you want to convert, it is better to retain the vertical dimensions and re-size horizontally. An odd number of pixels probably won't work. The number of horizontal pixels can be even for some encoders, but other encoders require a multiple of 4.

[TheLastOfThem]

Hi Everyone,

Is it better to retain anamorphic flag from a DVD (720x576) or make it 767x576?

Also for NTSC DVD's is 640x480 really identical to 720x480 in terms of detail ?

The DVD spec doesn't allow the use of square pixels. Use 720x576 for PAL and 720x480 for NTSC.

If you want to convert, it is better to retain the vertical dimensions and re-size horizontally. An odd number of pixels probably won't work. The number of horizontal pixels can be even for some encoders, but other encoders require a multiple of 4.

I won't be putting it back on a DVD .

So what do you suggest in making the size to retain the Aspect Ratio of the PAL rip for square pixels?

[El Heggunte]

............

So what do you suggest in making the size to retain the Aspect Ratio of the PAL rip for square pixels?

If the aspect ratio is 4:3 ==> then resize to 768x576

If the aspect ratio is 16:9 ==> then resize to 1024x576

You might also want to remove the black borders (letterboxing), but only if you think that saving a few kB or MB in the final filesize is important...

[pippas]

I agree with El Heggunte - that's the sizes I always use.

You might also look into whether it's a good idea to de-interlace as well. I think it is, but a lot of other folk don't.......it may depend on how you intend to keep and play your files of course?.....

[usually_quiet]

For a DVD with a 4:3 aspect ratio video, resize to 768x576 if it is a PAL DVD or 640x480 it it is NTSC DVD when converting to a different format that uses square pixels. Technically one might take the ITU spec into account when resizing some DVD video and crop a few pixels from the left and right, but not many DVDs follow the ITU spec.

[TheLastOfThem]

Thank you all so much. Is it true that DVD's still display 640x480 for NTSC sources? It's something called Pixel Aspect Ratio? Like your player resizes down? And for PAL it resizes upwards?

[TheLastOfThem]

So in reality....You aren't really getting a 720pixels wide pixture..?

[manono]

So in reality....You aren't really getting a 720pixels wide pixture..?

You get whatever the resolution your HDTV or computer monitor use. If, for example, your television is 1080p your video gets resized to 1080p as well. If the DVD is 16:9, 1920x1080. If 4:3, 1440x1080 with black bars added to the sides.

[TheLastOfThem]

But is 640x480 really the same image as the 720x480 image ? This is where I get confused

[Skiller]

The source picture of 720x480 may carry more detail than what is left after resizing it to 640x480. Though that's not often the case.
Anyways, you can use any resolution you want. So if you do not want to shrink to 640x480, then what about expanding to 720x540 instead?

[Cornucopia]

No it is not the SAME. But it's as close as you can get with a square-pixel equivalency, given vertical resolution constraints (particularly important with interlace-originated material).

Scott

[jagabo]

But is 640x480 really the same image as the 720x480 image ?

No it's not. By downscaling to 640 you are loosing ~11 percent of the resolution. And doing so may create moire artifacts. Later, when the TV or DVD player upscales to 1440x1080 those artifacts are going to be even more visible. Even upscaling PAL to 768x576 or 1024x576 may reduce quality.

I usually keep the original resolution (only cropping away black borders) and encode anamorphically with the same sample aspect ratio as the source. That way the video is only resized once -- during playback. The occasional exception is animated material which can be upscaled pretty well if you have the right tools.

Of course, if you use anamorphic encoding you must be sure your players support it.

[TheLastOfThem]

But is 640x480 really the same image as the 720x480 image ?

No it's not. By downscaling to 640 you are loosing ~11 percent of the resolution. And doing so may create moire artifacts. Later, when the TV or DVD player upscales to 1440x1080 those artifacts are going to be even more visible. Even upscaling PAL to 768x576 or 1024x576 may reduce quality.

I usually keep the original resolution (only cropping away black borders) and encode anamorphically with the same sample aspect ratio as the source. That way the video is only resized once -- during playback. The occasional exception is animated material which can be upscaled pretty well if you have the right tools.

Of course, if you use anamorphic encoding you must be sure your players support it.

I heard that upscaling the height is the worst thing you can do. Like making something 720x540 instead of keeping 480. I thought 720x480 was just the frame size? And that the TV/Player automatically applies a PAR of 8/9 for ITU? Making it naturally 640x480 on playback. Why would sizing is down to 640x480 non-square with no anamorphic flag lose 11%? Just because frame size of PAL DVD is 768 width-wise, does not mean the content is necessarily in that resolution does it?

[jagabo]

I heard that upscaling the height is the worst thing you can do.

Only for interlaced video. Every time you watch a DVD on an HDTV both the width and height are being upscaled.

Why would sizing is down to 640x480 non-square with no anamorphic flag lose 11%?

Here's a list of 10 integers.

0 1 2 3 4 5 6 7 8 9

Try to reduce that to 9 integers without creating any discontinuities. Or try converting it to 11 integers without creating discontinuities. You can't do either. Therein lies the problem with digital scaling.

Just because frame size of PAL DVD is 768 width-wise, does not mean the content is necessarily in that resolution does it?

The frame size on DVD isn't 768, it's 720. Try to resize this 720x576 image to 768x576 without creating artifacts.



Try upscaling directly to 1440x1080 vs a two step resize to 768x576 then to 1440x1080. which looks better?

[TheLastOfThem]

OK.

Doing the 720X576 to 768x576 made the right side of the image get affected heavily.

For the latter, doing direct to 1440x1080 was definitely less blurry.

So what you're saying is resizing of any kind is advised against? I assumed anamorphic flags were already resizing....so that counts right? So that's 1...then your 1080p TV upscales (thats another). If you resize before that fact...then it's like 3 resizes?

Wrong? Right?

[jagabo]

Anamorphic flags are not resizing. They are just a number or two in the file. They tell the player how to resize the video during playback. The player will directly upscale from the video's frame size to the required screen size. So when you use anamorphic encoding there is only one resize.

[usually_quiet]

You should consider how your videos will be played. Square pixels may be required by particular playback devices or needed for playback in a web browser. The same is true for deinterlacing. Other than that, it is up to you.

I prefer not to re-encode my videos, so I play a lot of interlaced SD video on my computer and pretty much all of it uses non-square pixels. I use software players that do a decent job playing it, so I don't find it to be a problem.

However a lot of people who come to VideoHelp with questions have expressed a preference for square pixels and deinterlaced video when watching on a computer, even in situations where it isn't strictly needed.

[TheLastOfThem]

So anamorphic isn't resizing? I assumed that's what anamorphic was doing when it tells it the display aspect ratio "multiply the height by this number" to get this number - 720 * 8/9 = 640

[LigH.de]

The video on a "DVD Video" disc is always anamorphic = skewed, squeezed horizontally. There are never square pixels on a DVD Video.

To watch the skewed video on a DVD conveniently, the player has to deskew it, as much as the aspect ratio flag defines. The MPEG-2 video in DVD Video discs uses target "Display AR" flags (width:height of the deskewed video, including possibly contained black borders, resize to a ratio of either 4:3 or 16:9). Other video formats may prefer "Sample AR" flags (a deskewing factor to multiply the width with).

You can either keep the material anamorphic during your conversion, then you will have to flag the copy with a similar aspect ratio flag to have the player deskew it while playing it. Or you can deskew the video while converting it.

[jagabo]

So anamorphic isn't resizing?

No. DVDs are already anamorphic. If you encode with the DVD's frame size and keep it anamorphic there will be only one resize operation -- when the player plays the video. Say you have a 720x576 4:3 DVD and you intend to watch it on a 1920x1080 HDTV. If you encode at 720x576 and play that video full screen it will only be resized once, from 720x576 to 1440x1080 (the player will add black bars to the sides to fill the screen rest of the screen). If you convert to square pixels and encode at 768x576, then play video full screen it will be resized twice, once by you from 720x576 to 768x576, then again by the player to 1440x1080.

I assumed that's what anamorphic was doing when it tells it the display aspect ratio "multiply the height by this number" to get this number - 720 * 8/9 = 640

No. It tells the player how to maintain the display aspect ratio. If yo play the video in a 480 line high window it will be resized to 640x480. If you play it at "half" size it will be resized to 320x240. If you play it at double size it will play at 1280x960. If you play it full screen on a 3840x2160 display it will be resized to 2880x2160.

If you resize to square pixel and always view the video at its native resolution on a square pixel display then there will be only one resize operation. But if you view it at any other size there will be two resizes. One by you, one by the player.

[TheLastOfThem]

So anamorphic isn't resizing?

No. DVDs are already anamorphic. If you encode with the DVD's frame size and keep it anamorphic there will be only one resize operation -- when the player plays the video. Say you have a 720x576 4:3 DVD and you intend to watch it on a 1920x1080 HDTV. If you encode at 720x576 and play that video full screen it will only be resized once, from 720x576 to 1440x1080 (the player will add black bars to the sides to fill the screen rest of the screen). If you convert to square pixels and encode at 768x576, then play video full screen it will be resized twice, once by you from 720x576 to 768x576, then again by the player to 1440x1080.

I assumed that's what anamorphic was doing when it tells it the display aspect ratio "multiply the height by this number" to get this number - 720 * 8/9 = 640

No. It tells the player how to maintain the display aspect ratio. If yo play the video in a 480 line high window it will be resized to 640x480. If you play it at "half" size it will be resized to 320x240. If you play it at double size it will play at 1280x960. If you play it full screen on a 3840x2160 display it will be resized to 2880x2160.

If you resize to square pixel and always view the video at its native resolution on a square pixel display then there will be only one resize operation. But if you view it at any other size there will be two resizes. One by you, one by the player.

Wow okay. I see...that really makes sense to me....wow. I see....Kind of mind blown a bit. I thought anamorphic was a resizing operation done by itself or something but really its just an info marker for the player...Makes sense. a lot of sense.

If the content is 640x480 on a DVD frame of 720x480...what does it look like? Because I don't notice it looking squished. What is PAR of DVD? Basically trying to figure out what a raw 4:3 image looks like

Thanks everyone for the wonderful explanations,

[manono]

If the content is 640x480 on a DVD frame of 720x480...what does it look like?

The content is 720x480 in an NTSC DVD. As already explained, when resized at playback (or if resizing to square pixel) the 4:3 content might get resized to any 1.33:1 ratio - 320x240, 512x384, 640x480, 720x540, 1280x960, 1440x1080, etc. - depending on a variety of factors.

You want to see how it looks as stored in the DVD VOBs? One easy way is to open a VOB in DGIndex and scroll around. It should be easy to tell that everything is slightly 'flattened' and people look slightly fat in 4:3 NTSC DVDs. Or go and find something round - a ball, sun, wheel or clock viewed head on - and it'll be even easier to see.

Here's an easy-to-follow article on DVD display aspect ratios:

http://www.doom9.org/aspectratios.htm

[TheLastOfThem]

If the content is 640x480 on a DVD frame of 720x480...what does it look like?

The content is 720x480 in an NTSC DVD. As already explained, when resized at playback (or if resizing to square pixel) the 4:3 content might get resized to any 1.33:1 ratio - 320x240, 512x384, 640x480, 720x540, 1280x960, 1440x1080, etc. - depending on a variety of factors.

You want to see how it looks as stored in the DVD VOBs? One easy way is to open a VOB in DGIndex and scroll around. It should be easy to tell that everything is slightly 'flattened' and people look slightly fat in 4:3 NTSC DVDs. Or go and find something round - a ball, sun, wheel or clock viewed head on - and it'll be even easier to see.

Here's an easy-to-follow article on DVD display aspect ratios:

http://www.doom9.org/aspectratios.htm

Very odd that they look fat in 4:3 too. I guess it's those nonsquare pixels of DVD...any way for me to photoshop and check?

[manono]

Very odd that they look fat in 4:3 too.

In NTSC DVDs people are fat in the unresized 720x480 4:3 DVDs and tall and thin in 16:9 DVDs.

any way for me to photoshop and check?

You want to capture a picture of how it looks as stored on the DVD? That same DGIndex can do that. Open a VOB, scroll to the place you want and then go File->Save BMP.

[TheLastOfThem]

Very odd that they look fat in 4:3 too.

In NTSC DVDs people are fat in the unresized 720x480 4:3 DVDs and tall and thin in 16:9 DVDs.

any way for me to photoshop and check?

You want to capture a picture of how it looks as stored on the DVD? That same DGIndex can do that. Open a VOB, scroll to the place you want and then go File->Save BMP.

If you can provide a capture - would love it

[jagabo]

Take any 4:3 square pixel image and resize it to 720x480. That will simulate how a 4:3 video looks on a DVD without compensating for the display aspect ratio.

[manono]

If you can provide a capture - would love it

A capture of what? You know, this video work requires a certain amount of ... initiative? Are you saying you don't know how to take pictures of DVD frames yet you are planning on using Photoshop for something related to this? Here, top picture from a DVD at 720x480. Lower picture, same frame at 640x480

[TheLastOfThem]

If you can provide a capture - would love it

A capture of what? You know, this video work requires a certain amount of ... initiative? Are you saying you don't know how to take pictures of DVD frames yet you are planning on using Photoshop for something related to this? Here, top picture from a DVD at 720x480. Lower picture, same frame at 640x480

Hi,

I know how to take pictures of DVD frames, I just don't have any available to me right now

And this goes back to what I was saying. 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.

From what I can tell a lot of 640x480 images are stored 720x480....so not understanding why on earth it would lose 11% or be assumed to lose .11111

[Skiller]

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.