VHS Aspect Ratio Processing Confusion
 

I'm trying to take on the task of converting some old home movies for my family and I admit I don't know much about this world.

When I got started I saw a lot of people recommending this capture/processing approach: https://www.youtube.com/watch?v=KdGDwNwmyVo

I don't have the tapes any longer and it would be a pain to get them back, so the raw files I captured with the above method (at timestamp 6:51) are what I'm working with.

In short:

- I captured the VHS tapes in 720x480 resolution. (which is a 3:2 ratio)
- When processing, the video above suggests to add a resize filter equal to 1920x1440 (which is a 4:3 ratio).
- The end result looks (as you'd expect) slightly squished and "off".

At first I figured the solution was as easy as not locking aspect ratio like the video suggests and keeping the original ratio, which would be 2160x1440, but then when I started googling I saw some tremendously in-depth different answers that went waaaay over my head about removing extra lines and using aspect ratios I've never heard of before.

I have these 720x480 videos - should I just resize to 2160x1440 or is there a better option? I have quite a few of these to do and I'd hate to have to repeat all this processing if I get it wrong.

SD VHS is usually 4x3 aspect ratio. Most home recordings will be this.
(Wide screen movies are often letterboxed with black bands at the top and bottom of the image.
Some recordings could have been made with anamorphic adapters on the lens but that would be unusual for home videos.)

Digitized SD video, including VHS, is normally 720x480 pixels (for NTSC)
480 because that is the number of scan lines in the visible image area.
720 pixels per scan line is the standard and is adequate to resolve SD video detail
This allows for 4x3 or 16x9 image by using non-square pixels.

The header information in properly configured digital video files normally provides this information to the playback/display system to ensure a proper image is displayed.
However, not all files contain the full information and not all playback/viewing system, interpret it correctly. Some display system may allow manual override of file aspect information.

There is no good reason to capture VHS tapes at resolutions higher than 720x480 (for NTSC). You just get bigger files with no additional useful information and may be forced into using lossy compression for the capture. The trick is to make sure the final distribution digital files include the correct information on aspect ratio, etc.

It should not look squashed, You are doing something wrong, Post a short sample.
Ideally 720x480 should be cropped to 704x480 getting rid of the black bands on the sides of the frame then resized to 1440x1080 or 1920x1440, It would restore the frame geometry perfectly. De-interlacing is recommended to avoid switching the field order.

Here's a frame from each video along with the metadata (easier to compare if you download and flip back and forth).

Attachment 15775
Attachment 15776
Attachment 15773Attachment 15774


The first screenshot is the original 720x480 capture from the VHS. The second shot looks squished after resizing in virtualdub to 1920x1440.

What I don't understand (I'm really bad with this stuff) is being squished makes sense because 720/480 = 1.5 and 1920/1440 = 1.3. Different ratios should produce an image with different ratios, no?

But everything I'm reading says that this should "work" and is how it's supposed to be done. So I don't get what I'm supposed to do to maintain the correct aspect ratio while also changing the aspect ratio? Clearly there's a piece my layman's brain isn't getting.

It goes back to pixel aspect ratio; the size and shape of each pixel (sample) in the image.
HD video uses a square pixel (aspect ratio 1)
Digitized SD NTSC uses a non-square pixel, ratio ~0.91 That grew out of the TV industry.
Your 1920x1440 assumes a square pixel.
That grew out of the computer industry that assumed square pixels starting with the VGA standards. (EGA, Hercules, AT&T's DEB, MDA, displays used different assumed pixel standards.)

The image in an analog video signal is comprised of scan lines of a specified duration. In conversion of an analog video signal (NTSC SD at 720x480) a pixel is presumed to be one scan line high and 1/720 (based on time) of the active scan line width. In DV the scanline active image is often 704 pixels, the rest blanked to avoid overscan issues.

To me the first (720x480) image has better detail.

Okay, that explanation of different pixel sizes makes enough sense.

I'm still not sure what I'd do (if anything?) to de-interlace and upscale without creating a warped image caused by the difference in pixel shape.

It's hard to tell from a screenshot, but when I compare the original 720 capture to the upscaled one, the upscaled one actually looks a lot smoother, nicer and higher quality - the aspect ratio just looks off because it's so different from the original 720 capture.

After deinterlacing, if you want to upscale, you start from the 1080 final heigth requirement and the DAR -> 1080 x 4/3 = 1440. Then you resize 720x480 to 1440 x 1080, which has a SAR=4/3, a DAR of 4/3 and a PAR=DAR/SAR=1. That's all.

If for whatever reason you want to build the fullHD frame you add 240 black borders each side to obtain 1440+240+240=1920 x 1080. Then your SAR will be 16/9, the DAR will be 16/9 and the PAR=DAR/SAR=1.

Remember to add in the final video the DAR flag or to tell to VLC (for example) the DAR ( VLC -> Aspect Ratio -> 4:3 or 16:9)

VLC player has its own aspect ratio processing so that's not a reliable screen shot, Post a short clip from the original raw video or just trust the members here, de-interlace 720x480 -> crop to 704x480 -> resize to 1440x1080. Note the words "crop" and "resize", they mean exactly what they do.

I know this is an old thread and you've probably fixed the issue by now. I ran across this thread when searching for answers and hopefully someone can help.

I'm experimenting with this same process (720x480 upscaled to 1440x1080) and followed the same steps mentioned above. I was confused because mediainfo says the resulting file's display aspect ratio is 1.212 and doesn't say 4:3 anywhere. When I play it in MPC-HC it does look squished with the default DAR setting, but when I change it to 4:3 it looks right and "Assume square pixels (SAR)" looks exactly the same as choosing 4:3. This is probably what's happening in VLC as well.

Is it safe to assume I've performed the upscale correctly?

PAR=1.212 is video with SAR=704/480 and DAR=16/9, because DAR = PAR * SAR.

I would say not. If a program won't play a video properly, there's something amiss because the file header info is giving out wrong info for the player to interpret.

What "process" are you using? I can't work it out from the thread.

In Vdub2, do as Latreche says: Crop Filter>crop the 8 pixels off each side. Then I would just go for square pixels: Resize filter>Aspect Ratio = Disabled, New Size=1440x1080. Export with a SAR of 1:1.

I was using Hybrid, following advice from the VideoHelp forum. Attached below is a screenshot of the settings. I'll try it in VDub and see what happens. It sounds like a more straightforward method for cropping. Will version 1.9.11 work for this? Note that in Hybrid I also tried unchecking "Force input PAR type", which made no difference.

Hybrid. I tried and gave up. Too many gotchas, tricks, things to miss.

1.9.11 has a poor-man's crop system; you basically have to add another filter first and then use the crop.

VDub 2 has a dedicated Crop filter so no shenanigans. It's no problem to use, just like 1.9.11, it runs in it's own folder and you can copy any of your filters into it's plugins folders (it has 32-bit and 64-bit plugins).

I have a guide for cropping in VDub 2:
http://aaproductions.net/virtualdub2...Anchor:58xL6lk

Board failure=dupe post.

This did the trick. Thank you very much. :congrats:

Great guide too. We need more guides like this. Clear and concise, with screenshots and no room for confusion. :salute:

This has also helped me realize what I did wrong in Hybrid. Simply leaving the PAR settings in the bottom-left at default (1:1) will output 4:3.

Thanks again.

Cheers Schlock, glad it was helpful.