Quantcast Fixing aspect ratio on VirtualDub? - digitalFAQ Forum
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03-10-2019, 09:59 PM
crissrudd4554 crissrudd4554 is offline
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Hello, I'm trying to do some test captures with VirtualDub but can't get the aspect ratio right. When I set it to 640x480 I get this. Correct frame size but image is slightly cropped on right edge.

vlcsnap-2019-03-10-22h52m19s216.png

Here it is set to 720x480. The cropped portion of the image is there but now the image is stretched.

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Anyway to fix this??


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  #2  
03-10-2019, 10:09 PM
crissrudd4554 crissrudd4554 is offline
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Another example using a different device. Set to 640x480 has the image slightly cropped on the left and right edges.

vlcsnap-2019-03-10-23h05m51s128.png

Same as other example when set to 720x480. Full image but image is stretched.

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  #3  
03-10-2019, 10:37 PM
sanlyn sanlyn is offline
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640x480 is a 4:3 aspect ratio. 720x480, which has a geometric 3:2 aspect ratio, has been the standard anamorphioc format for NTSC DVD is now the standard anamorphic frame size for SD BluRay and AVCHD; that frame size can be encoded to play at either a 4:3 or 16:9 aspect ratio. But as unencoded 640x480 or 720x480 AVI, the formats have no display aspect ratio and will always appear in the shape of their physical aspect ratio until they are encoded for a specific display aspect ratio (DAR). If the original image was designed to play at 4:3, the 720-wide frame will look stretched. if the original image was designed to play at 16:9, the 720-wide image will look horizontally squished. If encoded to play at the desired aspect ratio of 4:3 or 16:9, the image will look just fine when played.

Analog tapes can capture at 640x480 in the central 94 to 96% of the screen area with black borders on each side at anywhere from 6 to 12 pixels at left and right, and about 4 to 12 pixels of bottom border head switching noise. This has been the SMPTE (and similar) standard since Day One. Ever use a DV camera? At 720x480, the image from a real 4:3 DV video might just fill the whole frame but more usually analog tape will populate the central 704 pixels of the 720-wide frame. When encoded with your favorite DVD or BluRay encoder, those 720x480 frames will display at either 4:3 or 16:9 (it's your choice. Why don't you try it?).

What you might try is taking one of your favorite commercial DVD's and use the free trial version of DVDFab to copy the DVD video off the disc, remove copy protection, and convert it to MPEG files onto to your computer. Open the copied video in VirtualDub or another editor, and -- wow, guess what? The DVD frames aren't 4:3 (640x480) and they aren't 16:9 (856x480). The frames are either 720x480, 704x480, or even 352x480.

LS, I'm forced to say it again. It's getting really strange out there. I should stay away from subjects like this. From now on, I think I will. I'm running out of time anyway and despairing about stuff like this keeps me up at night.

Last edited by lordsmurf; 03-11-2019 at 10:40 AM. Reason: Edited, be nice!
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03-10-2019, 11:42 PM
crissrudd4554 crissrudd4554 is offline
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[If] you wanna be rude don’t comment at all. The reason why I hate asking for basically anything on sites like this or videohelp is because I run into [those] who come off like I’m supposed to know every aspect of what I’m actually seeking help with before I actually seek help with it. If that’s the case what’s the point of allowing people to seek help on these sites anyways?? We’re just 'supposed' to know?? It’s one thing if you folks wanna correct me and for the record I never claimed to be skilled in any field relating to this stuff. You sir are just bullying me. Second just about every site I’ve inquired about capturing VHS’ on has suggested I use VirtualDub. Well I’m trying, I have it in 4:3 and part of the image is cropped off. And yes I know 720x480 wasn’t gonna have it right. I was merely showing it to show how for some reason at that ratio the full image is there yet at 640x480 it’s not. I consider that somewhat of a flaw for a program apparently everyone recommends. So anyways I did not come here to be bullied. If that’s all you care to do than I’m wasting my time here.

See my reply below. -LS

Last edited by lordsmurf; 03-11-2019 at 10:43 AM. Reason: Edited. -LS
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03-11-2019, 08:59 AM
sanlyn sanlyn is offline
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I broke down information so you'd get it in small pieces and built it up to more complex matters. No, 720x480 is not "wrong" for VHS, but is usually the way people capture it because it offers greater working resolution for post processing and further encoding, and because if you want DVD or Bluray that's the format you'll need.

So let us all step back a bit:

I must be getting grumpy. or the coffee's weaker. One thing your post revealed is that you might have visited other tech forums, but maybe you got misguided. Digitalfaq has so many capture guides and restoration forums and projects that I can't see how anyone can spend more than a day in this forum and somehow manage to miss tons of it. When I first encountered tech forums like this I spent about two weeks getting my facts straight by browsing information that was already posted. Today it's getting to be more and more frequent that new visitors read less, and don't know how to find information in forums. Just looking, I guess, must be a learning project in itself.

Now, if someone gave you a series of guides and references, even if some of those guides and references might be a mixed bag of tech stuff, some dated but still relevant tutorials on how video projects have been conducted since the dawn of PC's, and the latest advanced guide to capturing and post processing, would you be willing to take up the invitation and start looking around? Or you could do it the easier way and go buy a $50 editor, but unfortunately your first step should be to dig into the product's user manual to find out what's inside. But people aren't following either of those routes. instead , they go straight to posting and bypassing years of knowledge and experience already posted. It just doesn't sit well with advanced users who know how to use forums to find information that's already there and has been there for years.

Maybe it's education: "Here, class, are the test questions and answers. You don't have to understand it. Just memorize it". Doesn't work that way with subjects like photo and video, where the mix is both science and art, where the variations are constant, and where the body of basic info and data is already out there, and new info and tech come along every day.

On this website there are some older guides. where the hardware might have changed but the basic principles still count: http://www.digitalfaq.com/guides/video.htm. Then there are newer guides for doing various things like capturing tape to a PC (Capturing with VirtualDub [Settings Guide]) or preparing certain types of data for encoded data for sampling, posting, or processing (How to upload a sample from DVD, MPEG-2 with DGindex [GUIDE]), and enough sample projects and advanced filtering guides to keep you occupied for several weeks at least, including some posted just within the past few days (Hi-8 Capture chain quality critique / advice), or fixing ugly video problems (Restoring VHS MPEG-2 transcoded tape?), or threads going back a long way such as many threads explaining how to use the controls and filters in apps like VirtualDub (post #16, post #17, post #19), or Avisynth and VirtualDub filters together (post #20) or rescuing a bad home video with Avisynth (post #21), or some debate/considerations about captures from a few weeks ago (Am I doing this video capture right?), or a catalog of capture and restoration projects posted after a query recently (post #10 and post #11), or a quickie fix for frame borders that doesn't require Avisynth (How to Properly Crop the Overscan in VirtualDub [GUIDE]).

Hopefully those links will help.

As for videoghelp they aren't as tech specific as they used to be (which is where I learned a lot up until a few years ago), but they do have a decent faq on video formats, PAL and NTSC: https://www.videohelp.com/dvd#tech, https://www.videohelp.com/hd#tech
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  #6  
03-11-2019, 11:11 AM
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Quote:
Originally Posted by crissrudd4554 View Post
Hello, I'm trying to do some test captures with VirtualDub but can't get the aspect ratio right. When I set it to 640x480 I get this. Correct frame size but image is slightly cropped on right edge.
Here it is set to 720x480. The cropped portion of the image is there but now the image is stretched.
Anyway to fix this??
A fix is not needed. Just simple understanding: aspect ratio is not aspect ratio.

You have DAR and SAR.
That is, storage aspect ratio, and display aspect ratio.
4:3 is DAR, but 720x480 is 3:2 SAR

So you capture right, just viewed wrong. But when working in an editor, you don't view as DAR, you view as SAR. The DAR is for when done, when watching on TV. Only when watching streaming does SAR=DAR.

Capture 640x480 is not ideal because you let the capture card make the choice on crop/resize, whereas you're usually better at it in software, if that crop is truly needed for streaming.

Make sense?

Quote:
Originally Posted by crissrudd4554 View Post
The reason why I hate asking for basically anything on sites like this is because I run into [those] who come off like I’m supposed to know every aspect of what I’m actually seeking help with before I actually seek help with it.
This is my pet peeve as well, and the reason I never do that to others. Generally speaking, anytime I see that happening in this forum, it is quashed. The person is reminded that not everybody knows everything. I like the Donald Rumsfeld musing about "unknown unknowns", meaning we don't know what we don't know. And again, we all have those. I'm here to try and help you understand what I know, partake my known unto you.

Quote:
Originally Posted by sanlyn View Post
I must be getting grumpy. or the coffee's weaker.
You are, and it is.

Quote:
LS, I'm forced to say it again. It's getting really strange out there.
Today it's getting to be more and more frequent that new visitors read less, and don't know how to find information
Maybe it's education: "Here, class, are the test questions and answers. You don't have to understand it. Just memorize it".
This is getting to be a problem. Not on this forum, or even about video, certainly not about anybody in this topic, but in general it is a problem in society. Even worse is not verifying what you read/hear/see, which leads to our current world political issues. The age of information brought on the age of mis/disinformation due to not researching and vetting. I wonder if that broader problem is clouding your mood on these forums. People that post on these forums are not your average dimbulbs, and are earnestly trying to solve an issue, having almost always done some degree of research already. So keep that in mind.

Quote:
I should stay away from subjects like this. From now on, I think I will. I'm running out of time anyway and despairing about stuff like this keeps me up at night.
Even if moody, your input is always valued, especially those Avisynth related topics. Heck, even I sometimes pick up tips from your scripts. So don't go anywhere.

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  #7  
03-11-2019, 03:30 PM
sanlyn sanlyn is offline
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You are right, of course. Next time, I'll type it in notepad first and wait 24 hrs.
No, crissrudd isn't stupid. Managed to start out making some screen caps. Some folks don't even get that far.
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03-11-2019, 04:00 PM
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Quote:
Originally Posted by sanlyn View Post
You are right, of course. Next time, I'll type it in notepad first and wait 24 hrs.
I still remember this lesson from college, in media courses. Back then it wasn't Notepad, but paper with pencil, so your can erase and re-write as needed. And I still practice it, and in Notepad. And sometimes to reply to PMs or post in this very forum. I also see posts where my first thought is "what the hell is this guy doing?!", I write an initial response in Notepad, re-read the post again the next day, and copy/paste the salient bits from Notepad, rewrite as needed. I don't want to knee-jerk respond, especially when having to be blunt, or a bearer of bad news.

But, back on topic ...

I think our OP here understands aspect ratios better now. And that's the goal.

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