Determining Aspect Ratios and Resolutions

[DJRumpy]

The whole reason for this guide is to understand how to do the math, or o understand how and why the math works. If they want a tool, they can always get one from the TOOLS section that will do these calculations for them.

[Roderz]

Very comprehensive info.
now I think I understand how to do the math.
But now I let excel calc it all 4 me. feed the figures into MainConcept and perfect dvd's with correct displays!
Cheers vey much

[sunmanking]

hello,

this is quite a peculiar case. so you might be interested in it.

i have a pal vhs capture from the tv. it's a film and it's letterboxed. i want to make a pal vcd (352*288).

the capture is at 352*288 (w*h) since i was interested in capturing at the same resolution as the pal vcd format.

using vdub and crop i learn that the real height (letterbox removed) should be 160. that is letterbox is on the top 64 on the botton 64, being that 128.

according to your guide, to remove letterboxing and keep the aspect ratio i should do the following:

352/288= 1.222

vcd display aspect ratio is 1.333 so...

288*1.333=384 width

384/1.222=314 heigth

that is: 384*314

now the letterboxing would be removed, wouldn't it?

however, our resolution is wider and taller than the pal vcd resolution (352*288)!!! how could it be? so what can i do here? since my main goal is removing the letterboxing AND following close to the vcd standard... if i input 384*314 to tmpgenc that will not output a standard compliant vcd at all.

what's more, tmpgenc let's you choose the aspect ratio. it is autodetected and in my case it has autodetected 4:3 625 line (PAL, 704x576). however this is not the real aspect ratio my video source has, as i have just explained above...

i am lost now...

please, any help would be welcome.

greetings,


sunmanking

[DRP]

hello,

this is quite a peculiar case. so you might be interested in it.

i have a pal vhs capture from the tv. it's a film and it's letterboxed. i want to make a pal vcd (352*288).

the capture is at 352*288 (w*h) since i was interested in capturing at the same resolution as the pal vcd format.

As it's a capture then I would have thought that the MPEG aspect issues would not yet be a problem like it is when when you rip from an already MPEGed source like from a DVD. Your aspect ratio is simply as it would be if it was an AVI - 352/160 = 2.2:1

I would simply stick it in TMPGEnc as I would an AVI file and specify 4:3 for the aspect ratio with an encode size of 352x288 with a letterbox window within that of size 336x160 to maintain the right aspect ratio and allow for the TV overscan.

[sunmanking]

hello,

As it's a capture then I would have thought that the MPEG aspect issues would not yet be a problem like it is when when you rip from an already MPEGed source like from a DVD.

well, i thought aspect ratio had to do with captures too not just with mpged sources.

now,

I would simply stick it in TMPGEnc as I would an AVI file and specify 4:3 for the aspect ratio with an encode size of 352x288

that is ok. just done.

with a letterbox window within that of size 336x160 to maintain the right aspect ratio and allow for the TV overscan.

here comes the problem. how can i make it with a letterbox window within that of size...??? i have played around with tmpgenc for a while but never had faced such an issue. i've had a good look at every option and setting and still don't know how to tweak it. could you please let me know? maybe you're referring the the cropping in vdub? but cropping would actually "erase" valuable" width image if we keep the source aspect ratio at 195x160, wouldn't it? or maybe you refer to resizing with vdub? but don't you think resizing would affect video quality a LOT? since it will be resized again in tmpgenc...

btw, you mention 336x160, that is an aspect ratio of 336/160=2.1 however, shouldn't it be 195x160=1.222 ? i mean, since the original capture aspect ratio is 1.222 (352*288) then 195x160 does keep the aspect ratio.

and last doubt...

thanks a lot for your reply.

greetings,


sunmanking

[DRP]

hello,

As it's a capture then I would have thought that the MPEG aspect issues would not yet be a problem like it is when when you rip from an already MPEGed source like from a DVD.

well, i thought aspect ratio had to do with captures too not just with mpged sources.

now,

I would simply stick it in TMPGEnc as I would an AVI file and specify 4:3 for the aspect ratio with an encode size of 352x288

that is ok. just done.

with a letterbox window within that of size 336x160 to maintain the right aspect ratio and allow for the TV overscan.

here comes the problem. how can i make it with a letterbox window within that of size...??? i have played around with tmpgenc for a while but never had faced such an issue. i've had a good look at every option and setting and still don't know how to tweak it. could you please let me know? maybe you're referring the the cropping in vdub? but cropping would actually "erase" valuable" width image if we keep the source aspect ratio at 195x160, wouldn't it? or maybe you refer to resizing with vdub? but don't you think resizing would affect video quality a LOT? since it will be resized again in tmpgenc...

Please search the Guides on this site for one by author "ElmarK". He has done only one guide so it's easy to find. There is a PDF file on his site with a section in it dealing specifically with aspect ratios, how to work them out and what settings to put in TMPGEnc to make it all work. It answers all the questions you have posed here.

[DJRumpy]

the capture is at 352*288 (w*h) since i was interested in capturing at the same resolution as the pal vcd format.

Even though your destination format is VCD, you should capture at a higher resolution. The reduction in size, when you resize it to VCD will actually help to reduce noise. It also gives you a conveniant excuse to pre-filter your capture as well, using a temporal or spatial smoother, to remove as much analog noise as possible.

352/288= 1.222

vcd display aspect ratio is 1.333 so...

Not quite right. Remeber that these calculations are based on NTSC figures. To make them work for PAL, you have to first convert it back to NTSC. To find that for VCD, you would have to find the VCD format's full width. Since it has a vertical height of 240 (ntsc), and the VCD format supports only a 4:3 MPEG aspect flag, you would multiply 240x1.333 to get 320. This is the part that confuses people. The VCD format has a 352 width, but the math we're doing says it should have a 320 pixel width. Just remember that the width, just like the SVCD format's width, is pretty much irrelevant to our end product. The math still works. Moving on...

Next, we convert your PAL video's image area height of 160, to NTSC by dividing it by .8334. That gives us 134 rounded (160 / .8334 = 134). Now you can do the math.

320 / 134 = 2.38, which, when placed into the closest aspect ratio, is 2.35 (you'll rarely find one that comes out exactly to the aspect ratio values...human error, cropping, etc will usually keep it a decimal or two off the expected aspect ratio decimal value). Your video has a 2.35:1 aspect ratio.

Ok, quick recap (remember these use NTSC values).
Find true horizontal width: 240 vertical * 1.333 = 320
Convert your video's vertical to NTSC: 160 / .8334 = 134
Divide the width by video's vertical to find the aspect: 320 / 134 = 2.35

Since your using TMPGenc, the rest is simple. Start the Wizard in TMPGenc, and pick the PAL VCD template. Use the Browse button when prompted to browse to your AVI or AVS file. Select '4:3 625 line (PAL)' for your aspect ratio and click NEXT. The next wizard page will let you specify your CLIP options (to remove the letterboxing from the top and bottom of your video). If you haven't edited your source to remove the letterboxing, check the CLIP option and input your top and bottom crop values. The next page will let you set your bitrate. On the last wizard page, make sure you UNCHECK the option to 'Start Encoding Immediately' and click OK. Click the SETTING button, and then Advanced tab, and set the 'Video Arrange Method' to 'Center'. This will resize your video to fullscreen, cropping off the left and rigth sides automatically. Your output will be VCD compliant.

[allvol]

I am in the process of converting a PAL Anamorphic (2.35:1) DVD to NTSC Anamorphic (2.35:1) DVD.

I have already converted the audo files from 25 fps length to 23.97 fps length. I have done the same with subtitles as well. I did a video transfer (sound and subtitles synced very nicely) but the aspect ratio was all screwed up.

Now I have found this thread.

The PAL Anamorphic DVD is 720x576. From what I read, its actual size (without borders) is 720x432? Now to encode for Anamorphic NTSC DVD and maintain the 2.35:1 aspect ratio, I would need to resize the video to 720x360 with 60 lines of black bars above and below to give 720x480? Or can I just resize from 720x576 -> 720x480 without removing bars and then adding them back?

[DRP]

I am in the process of converting a PAL Anamorphic (2.35:1) DVD to NTSC Anamorphic (2.35:1) DVD.

I have already converted the audo files from 25 fps length to 23.97 fps length. I have done the same with subtitles as well. I did a video transfer (sound and subtitles synced very nicely) but the aspect ratio was all screwed up.

Now I have found this thread.

The PAL Anamorphic DVD is 720x576. From what I read, its actual size (without borders) is 720x432?

No. That's not correct. If you're saying that the anamorphic letterboxing black bars top and bottom of the PAL DVD video amount to 144 pixels total (576 - 432), then the true width is not 720. The width is actually the display aspect ratio of the DVD - which will be 16:9 - multiplied by the video height *including* the letterboxing black bars.

Your true width is therefore 576 x 16:9 = 1024.

The true height is much simpler to work out. You just simply cut off the black bars and what you're left with is the true height = 432

The true aspect ratio is thus 1024 / 432 = 2.37:1[/quote]

[ricky1756]

Are you related to Dr. Shrink? Great guide

[DRP]

Are you related to Dr. Shrink? Great guide

Umm, are you being sarcastic? I can't tell. No, I'm not related to a Dr. Shrink. What I posted wasn't meant as a guide. I was merely pointing out something I think the previous poster had got wrong. I'm sorry if you disagree. I had a great deal of trouble working out aspect ratios in MPEG files myself, but I think I now have a pretty good handle on it such that I very rarely make mistakes anymore.

There are plenty of guides already written on the subject which describe in much geater detail what I briefly offered.

[ricky1756]

no, i'm not being being sarcastic, im complimenting you, because you both did nice things for the video community, free of charge

[allvol]

No. That's not correct. If you're saying that the anamorphic letterboxing black bars top and bottom of the PAL DVD video amount to 144 pixels total (576 - 432), then the true width is not 720. The width is actually the display aspect ratio of the DVD - which will be 16:9 - multiplied by the video height *including* the letterboxing black bars.

Your true width is therefore 576 x 16:9 = 1024.

The true height is much simpler to work out. You just simply cut off the black bars and what you're left with is the true height = 432

The true aspect ratio is thus 1024 / 432 = 2.37:1

[/quote]

Thanks. The 1024x432 is what would be displayed on a HDTV. However, when i look at the video in a video editor, the width is always 720. I assume that the HDTV stretches the width to the proper width of 1024.

So, essentially, the video should be resized to a height of 360. In the "file" the width will be 720 but its true width is 846?

I guess my question is do I need to resize the file from 720x576 to 720x480 or just cut 96 lines of black bar from the file? I am trying to convert from PAL Anamorphic to NTSC Anamorphic.

[DRP]

Thanks. The 1024x432 is what would be displayed on a HDTV. However, when i look at the video in a video editor, the width is always 720. I assume that the HDTV stretches the width to the proper width of 1024.

So, essentially, the video should be resized to a height of 360. In the "file" the width will be 720 but its true width is 846?

I guess my question is do I need to resize the file from 720x576 to 720x480 or just cut 96 lines of black bar from the file? I am trying to convert from PAL Anamorphic to NTSC Anamorphic.

Okay. You want to go from PAL DVD to NTSC DVD right? I'm not actually an expert on doing that as I don't have a DVD-writer, but I do make SVCDs from DVD everyday, so hopefully I can offer you some kind of assistance.

Here's what I would do. Firstly, find out the true dimensions of your DVD source without any black bars - picture only. Every PAL DVD I've ever seen has dimensions of 720x576, Interlaced with Top Field First and most have a 16:9 display aspect ratio. Most also have additional letterboxing (black bars) to make them the wider aspect ratios of either 1.85:1 or 2.35:1 when they get displayed on a TV.

So. Your picture width is 16:9 x 576 = 1024 as I have already explained.

The height in your example is 576 - 144 of black bars = 432.

So, what you have now is a picture of 1024x432. Forget everything else and don't confuse yourself. You've done the hard bit. The rest is easy. Just treat it like an AVI file from here.

I would then shove that into TMPGEnc and specify an MPEG-2 size of 720x480 (NTSC size) with "Full screen maintain aspect ratio" selected, specify your other settings as you see fit and encode with the appropriate NTSC settings.

It would be more complicated if you wanted to crop it and/or allow for TV overscan, but you haven't asked about doing that so this is about it.

[DRP]

Thanks. The 1024x432 is what would be displayed on a HDTV. However, when i look at the video in a video editor, the width is always 720. I assume that the HDTV stretches the width to the proper width of 1024.

Yes. That's right. I know it's confusing because I had great problems understanding it as well, but the *WIDTH* is unimportant. That 720 number is for a large extent meaningless. Try to forget about it. The *REAL* width is established from the HEIGHT. The height of the video is the important thing.

So, essentially, the video should be resized to a height of 360.

That would be the NTSC equivalent as I understand it yes. You don't need to specify this yourself though. You can just let TMPGEnc do it for you by selecting "Full Screen (maintain aspect ratio)"

In the "file" the width will be 720 but its true width is 846?

I can't figure out where you got that number from. The equivalent NTSC true width is worked out in exactly the same way as for PAL. It is the video height *including* all letterboxing multiplied by the display aspect ratio. Thus... 480 x 16:9 = 853

I guess my question is do I need to resize the file from 720x576 to 720x480 or just cut 96 lines of black bar from the file? I am trying to convert from PAL Anamorphic to NTSC Anamorphic.

I think you might be thinking that you can convert from one to the other by only cropping/resizing. I'm not sure as I'm not a DVD 2 DVD expert, but I don't think this is possible. I think you must re-encode and create an entirely new MPEG file with the new dimensions. I could be wrong though so hopefully someone else with expertise in this area will help you out. I was of the impression that you would need to re-encode the video again. I know I certainly do when I make SVCDs (which afterall are just slightly smaller DVDs anyway).

The only thing important about that 720 number is if you decide to do some cropping of that 720 "width" to remove black bars or to reduce the aspect ratio of the film as a whole, be aware that you will be cropping from that 720 dimension rather than from the true width of 1024, so you will need to compensate for that by a factor of 1024 / 720 = 1.42

[DJRumpy]

No need to do any math when converting from PAL DVD to NTSC DVD. Since you are not changing any of the aspect ratios, then you can simply resize from 720x576 to 720x480. The only remaining steps, are to slow down the video to 23.976 fps, and to slow down the audio. This is one of the easiest types of conversions, becuase your keeping everything else the same in regards to D1 resolution, and aspect ratio.

Resize it, letterbox and all.

[JustSomeGuy]

If dvd has the following image dimension available:

720 x 480
704 x 480
352 x 480
352 x 240

The aspect ratio's of these are:

720 / 480 = 1.5:1
704 / 480 = 1.46:1
352 / 480 = .73:1
352 / 240 = 1.46:1

I don't see how these resolutions are used to derive the standard
aspect ratios of 4:3 16:9 2.11:1 etc...
Unless the pixels are not square...

[Sulik]

Do not confuse Pixel Aspect Ratio and Display Aspect Ratio.

4:3 / 16:9 always refer to the display aspect ratio.
Pixels are rarely square, one example would be 4:3 display aspect ratio for a 640x480 frame -> pixels aspect ratio is 1:1 (square), and display aspect ratio is 4:3.

[JustSomeGuy]

So if I download a divx avi file how do I determ what the pixel aspect ratio is so that circles are circles and squares are square on a 4:3 or 16:9 display?

[irvie]

I am not sure if my problem is related to this topic. I extracted an MPG video from .bin and .cue files. TMPGenc DVD Author cannot open the mpg, saying that "the resolution 482x480 cannot be used in standard DVD." IS there a way to adjust resolution of MPGs so that TMPGenc will recognize the file and then able to author to a DVD?

Thank you for your help!

[DRP]

So if I download a divx avi file how do I determ what the pixel aspect ratio is so that circles are circles and squares are square on a 4:3 or 16:9 display?

AVI files do not support display aspect ratio flags. This confusion is only present when working with MPEG files. With AVI files, it is much simpler, what you see is what you get. If the AVI file has dimensions of 512x384 pixels for example, then it will always display at a ratio of 512 / 384 = 1.33:1 (or full screen on a 4:3 TV).

The only way you can change this ratio without introducing image distortion is to crop either the width or height by simply cutting off pixels and discarding that part of the picture.

[DJRumpy]

Just some guy, don't stress so much. Just remember that pretty much every movie out there will tyically comply with 1 of 3 primary aspect ratio's.

2.35
1.85
1.33 (4:3)

There are chances you might get something in between. If you do, then you have to adjust accordingly, but 95% of everything you see will fit into one of the three above. If I find an AVI that doesn't fit one of these, I will typically go do a google search to see what the dvd release or theatrical release aspect was, and resize accordingly. This assumes that whoever created the DivX didn't chop it into pieces . As you get familiar with each aspect ratio, you'll be able to spot them just by sight. If your not sure, just divide the width of your AVI by the height, and that will give you the aspect. No guessing invovled. As DRP said, AVI doesn't support aspect ratio, so they are displayed using their actual aspect ratio. What you see is what you get.

Irvie, you should create your own post. This thread is related to guide guestions. You'll get more responses in the main forum.

[chh]

Very useful info.

Re Tables 1 and 2 in the bottom of the guide: Would like to see the numbers of lines corresponding to aspect ratio 2.11:1 included. (Tmpgenc uses this ratio as source)

[DJRumpy]

I've been getting a few requests for that. I'll see about throwing them out there today.

[DJRumpy]

After a bit of research, I've come to the conclusion that the author of TMPGenc must have been smoking crack or drinking heavily when he wrote the text into the GUI.

He should have found a better way to label input/output settings, and mpeg flag settings, or found a better translator. Great piece of newbie software. Horrible use of the english language

chh, the setting your referring to isn't related to an input video's aspect ratio. That setting is for the output MPEG's DAR (Display Aspect Ratio) setting. It's also a typo. It should be 2.21:1, no 2.11:1. In addition, that setting should NOT be used for DVD Video. It is supported in the MPEG-2 specification, but not in the DVD MPEG spec. Use it only if your output MPEG-2 and NOT destined for DVD.

That said, on a whim, I went ahead and included the 2.20 aspect ratio in the tables and guide, to give a non-standard example of what aspects people might come across. Although there is a 2.21 video aspect ratio that is in use, it is used in approximately 6 total dvd titles in production, and all of those are region 2 dvd only. I also polished up the descriptive text for the Display Aspect Ratio, and Video Aspect Ratio, to hopefully help the reader better understand the difference between the two. Reading the last few posts, it seems there is still a lot of confusion as to the differences between the two.

Hope that helps!

Cheers - DJRumpy

[wwaag]

I've read this thread a couple of times and still have a question. What I want to do is display DV with a 1.33 aspect ratio on a 16x9 TV. Rather than cropping 60 pixels from the top and bottom, I want to simply add black bars to the side in order to maintain the original aspect ratio (the TV has a mode that adds gray bars to a 4x3 image which is really distracting). Using Vdub, I've arbitrarily resized the original DV to 540x480 and then added the black bars so that the final image is again 720 x 480. I then encode using a 16x9 DAR using CCE basic. The resulting image looks OK, but I'm sure there must be a more precise way than to simply "guess". Thanks in advance.

wwaag

[DJRumpy]

Just use a 1.33 (4:3) width of 640 pixels (widescreen is 852 in width).


For your image height according to your video aspect:
2.35 would use 272 pixels in height
1.85 would use 360 pixels in height
1.78 would use 384 pixels in height
1.33 would use 480 pixels in height

The rest of the vertical can be filled with letterboxing if your video is anything but 1.33 or 480 pixels in height.

Since your video is 1.33, you would resize to 640x480, and add letterboxing to the 640 to fill out the sides.

[absinthecarolinas]

Ok, I've posted a question in about every thread for every guide you've written but this one, so I guess we're due 8).

There's something weird about (S)VCD video with 2.35 A/R. If I rip a DVD which quite clearly has an aspect ratio of 2.35:1, and I want to put that on a standard (480x480) SVCD, the following math should be correct:

480 x 1.33 = 640 (true width)
640/2.35 = 272 (height for encoding)

So, I write a script like this:

lanczosresize(480,272)
addborders(0,104,0,104)  ## 480-272=208/2=104 top and 104 bottom

Problem is, this just doesn't display correctly at all. It's way too thin, and yes I'm definitely encoding it as 4:3 video. My TVs are all standard 4x3 (can't afford the 16x9 just yet ).

The same problem occurs with the math for VCD.

I played with the numbers a while, and as it turns out I get a correct visual result by using the same math I would use for a 1.85:1 A/R. Today, I encoded two movies with 2.35 A/R's for SVCD using this script ...

lanczosresize(480,344)
addborders(0,68,0,68)

I actually compared playback with the SVCD yielded from this script vs. playback of the original DVD itself by holding a piece of paper up to the television and measuring. It was correct. But it was definitely smaller (had more vertical border area) than a proper 1.85:1 movie encoded using the same script.

I also tested this with a VCD. I made a backup of my kids' DVD of "Peter Pan," the box of which reports the film to have an A/R of 2.40:1! I used -

lanczosresize(352,174)
addborders(0,33,0,33)

The result played back visually identically to the DVD (in size, that is, not quality :P).

Why is this? Or am I (as is usually the case) overlooking something very simple?

thx,

-abs

[DJRumpy]

I have no idea. It could be the way your player handles svcd. Mine always comes out identical to the source. The first I could understand as a possible misprint on the box or somesuch. I have also seen issues where the dvd player was setup with the display set to 16:9, when it was actaully a 4:3 tv. It gives you more image area, but your video is actually to tall.

[absinthecarolinas]

I have no idea. It could be the way your player handles svcd. Mine always comes out identical to the source. The first I could understand as a possible misprint on the box or somesuch. I have also seen issues where the dvd player was setup with the display set to 16:9, when it was actaully a 4:3 tv. It gives you more image area, but your video is actually to tall.

Well this is just weird. I've done the DVD-vs-(S)VCD-piece-of-paper comparison on two different players and the result is the same. I double-checked one of the players and it's definitely set to output to a 4x3 TV (I've lost the original remote to the other player so I can't check that one, but it's always seemed correct).

I'm really scratching my head over this one. Let me clarify: if I resize to what should be mathematically correct, the picture's aspect ratio really is correct inasmuch as the shape of the picture itself appears 2.35:1. But the picture still appears squished, as though the A/R were supposed to be 1.85, even though I'm positive that's not the case.

There's definitely something to this; the phenomenon even seems to occur previewing in Media Player Classic.

Here's a capture from a movie with a 2.35:1 A/R encoded to MPEG1 for VCD sized at 352x136 with 52 pixel borders top and bottom (which ought to be correct), as previewed in MPC:


And here's the same scene sized at 352x176 with 32-pixel borders:


Weird. Any ideas?

-abs