Determining Aspect Ratios and Resolutions

[Bardmaster]

DJRumpy, I'd love to hear how you've fared in your quest for the perfect codec and encoding solution (software, settings, etc.!). Check out my recent post! I'm also building a media server and would like to keep my movies at a decent size while still having good quality for an LCD TV.

https://forum.videohelp.com/viewtopic.php?t=320071

Relevant to this post: after encoding letterbox movies to DivX or XviD I've found the black bars on top and bottom cut further into the video by about 1 inch each! In other words, compared to viewing from the DVD player on the same LCD TV, my streamed avi video is getting "squished" vertically! Any ideas why?

[DJRumpy]

Your TV will normally overscan a video from a source like a dvd which takes away about an inch on all sides. That makes the black bars look a bit smaller. When you view them with a media pc however, most people adjust the video output so that there is no overscan (so that your windows desktop doesn't get it's edges chopped off), and that alone will make the black bars appear a bit bigger. That is the most likely cause for the difference your seeing.

As to your question regarding the perfect codec, I would have to say the best option right now is x264 (check out MEGUI for your tool of choice). Makes excellent copies at around 800-900 kbps at full dvd resolutions.

[Bardmaster]

I don't think my MediaLounge supports x264 but I'll check it out, thanks!

Any solutions to the "lack-of-overscanning" issue? If I want the video to fit more screen space, do I simply have to increase the resolution? I understand I should do this in multiples of 16 for maximum compatibility. Obviously this would cut off the left and right edges of the video - this is technically what normal TV output does to 16x9 letterbox video, right?

So if the resolution is 720x308, perhaps increasing to 752x340 would fill the screen better - again, understanding there would be some video cropping on the sides.

[DJRumpy]

No, changing the size of the video would do nothing as it would still be scaled to fit the screen edge to edge. To reduce letterboxing you would have to chop off the left and right edges of your video.

If your source video is 640x272 and you had a 4:3 TV, you could crop it down to 480x272, and it would fill a 4:3 tv screen. Get the idea? I would never recommend it. It's an extreme fix just to get a video to fill the screen. If you don't have a widescreen then think about the fact that you probably will in the next few years.

[Bardmaster]

I think I figured out my issue: the s/w I was using (InterVideo DVD Copy 5 Platinum) was taking the 16x9 source and creating a 4x3 output! I assumed it would keep the source aspect ratio, but I guess this program is not very smart. So the TV likely has to squash to keep the entire picture on its screen.

I'm trying out AutoGK 2.40 now, because several people recommend for XviD and DivX encoding.

[graysky]

Great guide man. If I'm understanding it correctly, can you guys check my work here:

DVD rip with 16:9 DAR (that's what Stream Information.txt that dvd decrypter tells me). It is 720x480 and when I crop the black bars out I lose 124 pixels totally (480-124=356). So the math is 720*1.778=853 for the new width and from your guide, I take 853/356=2.39 which matches the 2.40:1 that the DVD box advertises. OK!

Now I know my signaling AR needs to be 12:5 but what do I encode my video to keeping mod16 in mind? 720x352?

I don't care if this is DVD compliant or whatever, I'm just going to play it in mplayer but mplayer reads that signaling AR and scales accordingly. So I guess I need to understand how me taking away those 124 lines will change what I encode to size-wise.

Does that make sense?

[graysky]

Update: When I play the resulting file in mplayer it thinks the AR is 2.04:1 and NOT 2.40:1. Here is the output:

VDec: vo config request - 720 x 352 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 2.05:1 - prescaling to correct movie aspect.
VO: [directx] 720x352 => 720x352 Planar YV12

I can get it to play correctly if I do a

mplayer -aspect 12:5 movie.mkv

which gives this partial output:

VDec: vo config request - 720 x 352 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 2.40:1 - prescaling to correct movie aspect.
VO: [directx] 720x352 => 844x352 Planar YV12

[DJRumpy]

MPlayer is usually good about respecting embedded apsects, even in DivX/XviD files. I always use mod16 of 352 for 2.35, and it works well for 2.40 as well.

Sounds like it's not picking up an embedded SAR in your first example. In the second one, you telling it exactly what the SAR is, and it resizes it properly on playback.

[graysky]

Yeah, it's a problem with MeGUI. When I set the AR in mkvmerge GUI, it works just fine.

VDec: vo config request - 720 x 352 (preferred colorspace: Planar YV12)
VDec: using Planar YV12 as output csp (no 0)
Movie-Aspect is 2.40:1 - prescaling to correct movie aspect.
VO: [directx] 720x352 => 846x352 Planar YV12

Notice the prescaling to 846x352 line. The solution to this problem was to take MeGUI out of the loop and manually set the aspect ratio from within mkvmergeGUI. I simply used 12/5 for the video stream. Here is the resulting commandline it used

"mkvmerge" -o "D:\work\V\trial\forced 12to5 in mkvmerge"  --language 1:eng --default-track 1:yes --aspect-ratio 1:12/5 -d 1 -A -S D:\work\V\trial\megui.mkv --sync 0:0 -a 0 -D -S "D:\work\V\trial\audio.ogg" --track-order 0:1,1:0

Now the question in my mind is what the hell are the global MeGUI_darx = x and global MeGUI_dary = y good for if they don't get passed on to the muxer? Is this a bug or is this me?

[graysky]

@DJRumpy: Can you take a look at the related question in this thread for me? Now that I have mastered this whole anamorphic stuff, I wonder which would better preserve the source quality.

[DJRumpy]

Bizarre. Thee they work perfectly for me every time. You might try a wipe of your MeGUe install and let it re-update with the latest code. I've noticed mine gets gacked every few months and some items don't update properly.

I'll take a look at the other thread.

[graysky]

Thanks... so when you rip a movie and make your avs script in megui, you overcrop and the resulting global MeGUI_darx=x and global MeGUI_dary=y are correct?

They aren't for me even after a reinstall. For example, the 2.40:1 movie is detected as 87/35=2.48:1.

It got the 1.85:1 movie correctly and the 16:9 movie correctly though. Other problem is it still doesn't pass those to the muxer :/

[DJRumpy]

Correct. Just use the built in AVISynth script creator. Auto Crop, and then select the 'Clever (TM) anamorphic encoding'. The source DAR will be selected automatically and the global SAR variables will be set in your script.

[meldavid]

Hi, if I have an avi that is 640 x 368 (aspect ratio of 1.739), and want to create a 16:9 DVD, is this script correct?

AddBorders(8,0,8,0)
LanczosResize(720,576)

Basically I just added borders to the left and right sides (rounded to nearest 4) to give an AVI that is closer to a 16:9 aspect ratio.

368 * (16/9) - 640 = 14.2222222
14.22222 / 2, rounded to nearest 4 = 8

So avi is now 656 x 368 (1.783 aspect ratio) which gets resized to 720 x 576.

Am I going about this the right way? I can understand the maths when the aspect ratio is greater than 1.7777777 but get confused when it is less. I prefer to add letterboxing than cropping the sides.

[DJRumpy]

This is correct. Your source AVI is 1.78 and you've resized it to the proper DVD resolution.

When the aspect is less than 1.78, you would simply add letterboxing to the left and right sides (say for a 1.66 aspect), or it it's 1.333 (4:3) you would just resize it to 720x576.

[jagabo]

Hi, if I have an avi that is 640 x 368 (aspect ratio of 1.739), and want to create a 16:9 DVD, is this script correct?

AddBorders(8,0,8,0)
LanczosResize(720,576)

In all likelihood the original source was 16:9 and was resized to 640x368 because 368 is an even multiple of 16 (MPEG codecs are at their best with multiples of 16). So simply resizing to 720x480 would probably work just fine.

[hydrophonicaudio]

This thread has been invaluable in helping me with re-sizing and re-encoding video that I backup from my DVD's. I do have a question though. Occasionally I get video files that my family wants to see so I re-size it for Widescreen and through it on disc for them. One of the files that I received recently has a size of 576 X 432. Obviously, it was encoded for fullscreen viewing. But I'd like to re-size it for Widescreen aspect so that it's in 16:9 format on disc. I tried using your formula so that I re-size it as close to 720 X 480 as I could get it, but I'm getting some weird numbers.

When I divide 576 by 432 I get 1.333;Then dividing 852 by 1.333 I get 639 which I KNOW is wrong since the height can't be greater than 480. I thought of maybe just leaving the height at 432 and re-sizing 576 to 720 and adding padding to compensate for the difference between 432 and 480. But then I realized that the picture would be horribly dis-proportioned. I'd really like to have this movie encoded in Widescreen format....is their anything that I can do to accomplish this?

[DJRumpy]

This is simple enough, although you may find the output a little too cropped depending on your input. You would simply chop off a bit of the top and bottom to convert Full Screen to Widescreen.

To convert 4:3 video to 16:9 (the closest widescreen resolution), you would crop a 640 wide video's height to 360 (352 if you want to retain a number divisible by 16). You do that by dividing the AVI's width of 640 by the aspect ratio you want to convert it to (640 / 1.77 = 360 ).

If you're burning that to DVD, then you would resize that cropped video to 720x460 and then add letterboxing of 10 on top and 10 on bottom to fill out the 460 to 480.

If your content LOOKS cropped when cropping it to a widescreen resolution, you can always crop it to something in between 1.33 and 1.76 video and then resize that to a 1.77 widescreen aspect. It may look a tiny bit 'short' but it won't crop as much (something like cropping it to a 1.5 aspect ratio and then resizing that to a 1.77 aspect).

That would crop a 640 width video to 640 x 426 (640 / 1.5 = 426 ) and then resize that to 720x460 and then add the 1.77 letterboxing of 10 on top and 10 on bottom. Kind of a hybrid fullscreen to widescreen approach that doesn't crop quite so much.

Two possible options depending on your source and preferences.

[FulciLives]

This thread has been invaluable in helping me with re-sizing and re-encoding video that I backup from my DVD's. I do have a question though. Occasionally I get video files that my family wants to see so I re-size it for Widescreen and through it on disc for them. One of the files that I received recently has a size of 576 X 432. Obviously, it was encoded for fullscreen viewing. But I'd like to re-size it for Widescreen aspect so that it's in 16:9 format on disc. I tried using your formula so that I re-size it as close to 720 X 480 as I could get it, but I'm getting some weird numbers.

When I divide 576 by 432 I get 1.333;Then dividing 852 by 1.333 I get 639 which I KNOW is wrong since the height can't be greater than 480. I thought of maybe just leaving the height at 432 and re-sizing 576 to 720 and adding padding to compensate for the difference between 432 and 480. But then I realized that the picture would be horribly dis-proportioned. I'd really like to have this movie encoded in Widescreen format....is their anything that I can do to accomplish this?

The image you have that is 576x432 ... is it 4:3 Letterboxed or 4:3 Full Screen? If it is 4:3 Letterboxed then you need to figure out how much needs to be cropped from the top and bottom so that just the image is seen and none of the black because if it is 4:3 Letterboxed then it should have black above and below the image. Once you have the proper height less the black you can figure out how to properly resize for a 16x9 WS display.

If it is 4:3 Full Screen then you can only make it anamorphic by either adding black to the sides (to maintain the aspect ratio) or you need to either cut into the image or stretch the image and either way you ruin it.

- John "FulciLives" Coleman

[DJRumpy]

Hmm..good point. Is your source a widescreen video encoded to a fullscreen aspect? In other words does your encoded video have letterboxing? Those are fairly rare for video encoded to AVI but it does pop up from time to time if someone encoded it without stripping the letterboxing.

If so, crop off the letterboxing and then simply divide the width by the height on the cropped video to figure out what aspect it really is.

[hydrophonicaudio]

The image you have that is 576x432 ... is it 4:3 Letterboxed or 4:3 Full Screen?

There is no letterboxing in the video at all. It is 4:3 Fullscreen. Since I'm using VisualHub on the Mac, I'm thinking of just leaving it as is and enabling the "Force Anamorphic 16:9" option when I encode for DVD.

[FulciLives]

The image you have that is 576x432 ... is it 4:3 Letterboxed or 4:3 Full Screen?

There is no letterboxing in the video at all. It is 4:3 Fullscreen. Since I'm using VisualHub on the Mac, I'm thinking of just leaving it as is and enabling the "Force Anamorphic 16:9" option when I encode for DVD.

I'm not sure what that option does ... don't have a MAC ... but you should either encode as standard 4:3 or if you encode at 16x9 you want to make sure you get a standard 4:3 image with black on either side. If you do it the 2nd way then those with a 16x9 WS TV will be forced to watch it in the correct aspect ratio in that the image will be centered at 4:3 with black on either side. However on a 4:3 TV the image, while in the correct aspect ratio, will have black on all 4 sides of the image.

If you want the image to fill a 16x9 WS TV then the only way is to either stretch the image to fit (which looks weird if you ask me) or to crop the top and bottom so that it will fit ... but then you are cutting into the image and that could cut information that is needed for a proper image.

- John "FulciLives" Coleman

[DJRumpy]

In that case you can follow my original advice if you like and crop the 4:3 video to a widescreen aspect ratio (assuming you want it to look right on a widescreen TV without letterboxing of any sort).

It's not necessary to add letterboxing to your video's left and right sides when encoding for a 16:9 display. It will automatically add that letterboxing on playback assuming the Display Aspect Ratio flag is set as 4:3. Your player will 'pillar' the playback with letterboxing.

[holeepassion]

This is a very enlightening topic as I am trying to create a DVD from 640 x 480 avi videos. I was thinking how do I get a DVD solution with such a small resolution.

Thanks very much for your kind and generous effort on this.

Just to clarify that I get it right though. I did not get it the first time I read but I think, I sorta get it now especially wit the tables.

Now, being in Australia, if I want to create a DVD, in PAL, then I have to get the display aspect ratio of 720 x 576. I am just wondering there are a lot of options. Are the bigger the number, the better it is, or the actual ratio ( I meant as compared to the like of 720 x 480 for example, by memory). Since I might be producing the DVD for playing on NTSC TV format also, what is the best way to serve both ??? What are the compromises if any ?

I am going to be using the deshaker where it asks for the source pixel aspect, which I think is the 640 x 480 figure. Now, the selection with the ratio of 1.333 is HDV 1440 x 1080 and this is the only option, does this affect anything ? or it is the ratio that matters ???

Thank you very much for your anticipated responses.

Best regards

PS:

I also have questions regarding how to avoid degrading resolution in the process of editing avi files in virtualdub, wax and other commercial packages like Sony Vegas ??? What do I have to watch for ???

Secondly, I also like to create slide show of pictures in Wax, where the pictures have a much higher resolution of 2816 x 2112. I am wondering if I need to change the pixels or not ? I am concerned about the quality if I reduce it ?

Thank you

Best regards

[FulciLives]

You need to decide if you want to do NTSC DVD or PAL DVD as they are different.

NTSC DVD is 720x480 whereas PAL DVD is 720x576

In short you would resize from 640x480 to either 720x480 for NTSC DVD or 720x576 for PAL DVD. If you want to be 100% proper then you should actually resize to a width of 704 and you can encode it as 704 or you can add 8 pixels of black to either side which would make it a width of 720 ... the later method (resize to 704 with 8 pixels of black on either side to make it 720) is the more common way.

Also you need to consider the frame rate of the original AVI video. If it is 25fps then that makes it PAL whereas NTSC can be 23.976fps or 29.970fps. Now you can still take a 25fps AVI and make a NTSC DVD instead of a PAL DVD. You can also take a 23.976fps AVI and make a PAL DVD instead of a NTSC DVD. However you have to be careful how you handle the frame rate difference. The easy way is to use DGPulldown if needing to go from 23.976fps to 25fps or vice versa.

If the AVI is 29.970fps then it would be best to make it a NTSC DVD.

- John "FulciLives" Coleman

[holeepassion]

thanks Fulcilives ... now NTSC DVDs be played on PAL system ?D
or do I need to create both ? what is the common practice ?
For example: people making DVDs cater for PAL countries versus NTSC countries ... do they produce two separate DVDs ? How about for computer playing ? Is that different again ???

Thanks

Happy New Year by the way !!!

PS: been checking out VirtualDubMod, is it worth it compared to just VirtualDub ??? since the release on VirtualDub is more current ?

[holeepassion]

OH .... I am a bit confused with the resizing bit still I think .. if I add the 8 pixels on either side ... would it be displayed on TV set ? It looks kinda ugly isn't it as compared to the top and bottom style ???? If I let the software system resize, would they degrade the resolution much ???

The frame per second is 30, so I guess NTSC is the more correct system then ???

Thanks again ...

[zardano]

I typically convert 4:3-Letterbox DVDs to anamorphic widescreen so they will play correctly on widescreen TVs. (I did this with the 2.35 "Bonus discs" of the star wars trilogy and it worked nicely).
Now I have a NTSC DVD with 4:3-LBX encoding at 1.66:1 ratio. Since 1.66 is less than the 16:9 DAR flag of 1.78, is it even possible to do this, and if it was encoded/compiled as a 16:9 DVD would it display any differently on the widescreen tv?

Using the math in the guide, 852/1.66 = 513 (round to 512), but NTSC only has 480 lines to work with. I imagine I could resize the height, and allow the 16:9 DAR flag to squeeze the video to the proper ratio, but I'm having a hard time figuring out the math, and again, if this would even change anything when played back on a 16:9 TV.
The black bars are 42 and 50 from vdub's null transform, so I would do:
Crop(0,42,0,-50)
but I don't know what to resize the video to, and then what amount of borders to add.

Maybe its 4:3-letterbox on the source DVD for a reason..

[FulciLives]

thanks Fulcilives ... now NTSC DVDs be played on PAL system ?D
or do I need to create both ? what is the common practice ?
For example: people making DVDs cater for PAL countries versus NTSC countries ... do they produce two separate DVDs ? How about for computer playing ? Is that different again ???

Thanks

Happy New Year by the way !!!

PS: been checking out VirtualDubMod, is it worth it compared to just VirtualDub ??? since the release on VirtualDub is more current ?

NTSC countries do not favor PAL at all ... in short you can expect a NTSC country to only be able to play back NTSC and not PAL ... that is how most equipment is in a NTSC country.

PAL countries are a bit more favorable to NTSC and from what I have read most PAL DVD players and televisions will have no issues playing back a NTSC DVD.

A computer can just as easily play back NTSC and PAL so no such issues exist on a computer as to which format the DVD is in.

If you want to make a DVD that you intend to sell to both PAL and NTSC countries then it makes the most sense to make two releases ... one in NTSC and one in PAL.

OH .... I am a bit confused with the resizing bit still I think .. if I add the 8 pixels on either side ... would it be displayed on TV set ? It looks kinda ugly isn't it as compared to the top and bottom style ???? If I let the software system resize, would they degrade the resolution much ???

The frame per second is 30, so I guess NTSC is the more correct system then ???

Thanks again ...

Most televisions have TV OVERSCAN which means the image is slightly "blown up" so that the extreme edges (top, bottom, left, right) are masked i.e., outside the visible range of the TV. So in short very few televisions will show those 8 pixels of black. You can just go ahead and go straight from 640 to 720 but technically this will produce an aspect ratio error ... however the error is so little that it is not noticeable by the naked eye.

If that AVI is 30 fps (I'm assuming it is 29.970fps) then you are better off making a NTSC DVD from it.

- John "FulciLives" Coleman

[FulciLives]

I typically convert 4:3-Letterbox DVDs to anamorphic widescreen so they will play correctly on widescreen TVs. (I did this with the 2.35 "Bonus discs" of the star wars trilogy and it worked nicely).
Now I have a NTSC DVD with 4:3-LBX encoding at 1.66:1 ratio. Since 1.66 is less than the 16:9 DAR flag of 1.78, is it even possible to do this, and if it was encoded/compiled as a 16:9 DVD would it display any differently on the widescreen tv?

Using the math in the guide, 852/1.66 = 513 (round to 512), but NTSC only has 480 lines to work with. I imagine I could resize the height, and allow the 16:9 DAR flag to squeeze the video to the proper ratio, but I'm having a hard time figuring out the math, and again, if this would even change anything when played back on a 16:9 TV.
The black bars are 42 and 50 from vdub's null transform, so I would do:
Crop(0,42,0,-50)
but I don't know what to resize the video to, and then what amount of borders to add.

Maybe its 4:3-letterbox on the source DVD for a reason..

There are 16x9 WS anamorphic DVD Videos on the market. How do they do it? Well since 1.66:1 is not as "wide" as 1.78:1 you have to have black on either side of the image to make up that extra space.

Think about it. It really isn't that different from encoding 1.33:1 for 16x9 WS anamorphic. With 1.33:1 you make it so it fits from top to bottom and then add black to either side to take up the extra space where there is no image. You do the same thing with 1.66:1 or any ratio that is less than 1.78:1

As for the math ... that can get tricky but FitCD should be able to help you figure it out. FitCD is a great tool for working out how to resize from one format to another.

Here is an example from a commercial NTSC DVD that is 16x9 WS anamorphic but has an aspect ratio of 1.66:1
For this example I am using the single disc release of THE ROCKY HORROR PICTURE SHOW (UPC Code: 024543051008)

Here is the image as it is stored on the DVD Video disc ... this image is 720x480 resolution:


When you adjust this for the proper aspect ratio you have to resize it to 852x480 resolution:


Using this as an example there is approximately 28 pixels of black pixels on either side of the image (actually it is 30 on the left and 28 on the right). This leaves an image of 662 width wise (when you cut 30 from the left and 28 from the right). I am of course talking about the first image (the one that is 720x480 resolution).

Now let's get to your issue at hand. You have a 4:3 video source and the image is approximately 1.66:1 inside of that. To convert this to 16x9 WS anamorphic you would have to first crop the image which means cutting off the top and bottom ... which will give you something less than 480 (assuming you have a 720x480 4:3 source to begin with). I can help with the math if you can post an image of the original unedited frame ... use VirtualDub(Mod) for this or AviDemux etc. and please be clear if you are going from PAL to PAL or NTSC to NTSC etc.

Note that using my example of RHPS we would expect to take your cropped image and resize it to 662x480 and then add 29 pixels of black on either side. However the exact resize will depend on what you are left with after doing your crop ... in other words the aspect ratio might not exactly match that of RHPS or be exactly 1.66:1

So if you can post that image of your source I will work out the correct resize and fill plus do my best to explain how I did it.

- John "FulciLives" Coleman