Fixing horizontally stretched video

[robjv1]

I have a homebrew DVD that was originally 4:3 footage captured from a VHS tape (I don't have the tape) at 352x480, but the actual frame itself (the visible picture) is also stretched quite a bit horizontally to the right (everything looks too wide, although not as wide as something stretched to 16:9 would look) I need to convert it to 720x480 eventually, but I need to reduce the overall horizontal stretching of the visible frame, as I plan on matching it with another source that is 720x480 and in the correct aspect ratio, and since there is motion involved I have to get the visible frames to be exactly the same size.

I'm just not sure where to begin or how to go about it properly -- is this something I can accomplish with virtualdub and avisynth, or will I need something else? I'm imagining that I will need to resize the video to fix the horizontal stretching first and then superimpose it over a 720x480 masked black frame of some kind.

Thanks in advance!

[poisondeathray]

Do you mean the 352x480 footage has the wrong AR flagged (16:9 instead of 4:3) ?

Why do you say "horizontally to the right?" Is it only in 1 direction ? not left & right ? That comment suggests something else might be up... If it was proportional , you could just resize it normally and set 4:3 flag when encoding

How are you determining this? in a media player or some other application ?

The other footage you want to match with is 720x480 4:3 ?

[robjv1]

Thanks for the quick reply.

I determined it in MPEG Video Wizard, which I often use to match footage like this.

I ripped the footage directly off the DVD -- 352x480 is the resolution (half D1 DVD, I imagine) and I'm combining it with my own footage that is 720x480. Resizing the 352x480 footage up to 720x480 results in the same problem, it's stretched horizontally within the frame.

After looking at it more closely, it appears that it is stretched equally across the frame. I took two identical frames from each source and overlayed them on top of each other in Photoshop (creating two layers), lined them up, and then put a mark on a facial feature in both frames, on both layers. Switching back and forth between them, it appears to be stretched several pictures in both directions. This makes sense, since I believe this was originally recorded with a DVD recorder and I doubt this person would have done anything very wacky to it (though I'm starting to wonder). It does not appear that it is flagged as 16:9 though as you see below.

Gspot reports that the 352x480 source has a SAR of 11:15, PAR of 20:11 and a DAR of 4:3. The footage I want to match it with has a SAR of 3:2, a PAR of 8:9, and a DAR of 4:3.

[poisondeathray]

If it's even, you should be able to resize normally , if those Gspot numbers are accurate...

However , if it's interlaced, you have to resize in an interlace aware fashion (you could use vdub and checkmark interlaced resize) , or do a special interlaced resize in avisynth

But you're saying it looks too wide in Womble ?

If you view it 1:1 it should look horizontally squeezed . If it had incorrect 16:9 flag , gspot should have reported it . So something is still fishy here... What happens when viewed in a media player ? like VLC, or MPCHC, or KMplayer ?

[robjv1]

It's the same problem, it's slightly horizontally stretched in all applications, Womble and all video playback applications, both as a 352x480 video and as a 720x480 resize. It is interlaced footage. I resized it in Virtualdub using the interlaced setting and it looks stretched still, as you may be able to see below. Something fishy indeed!

It's almost as if in my original version (the top image), there is a small amount of normal black space around the frame (about equal on the top and bottom, although the image is shifted too far to the right, by about 8 pixels, shifting it back reveals about equal amounts of black space around the image) where in the other version (the bottom image), the image itself has been stretched across that same space, pushed to the edge of the frame on both the right and left side.

Centering both frames on top of each other (or as best as possible in this case) reveals that the bottom is slightly horizontally stretched in comparison to the top frame in both directions. Oddly enough though, the second image doesn't appear to be cropped, which was my first guess.


It's hard to tell from the pictures, but when cutting between the two clips in video, the difference becomes apparent. I will often cut between 4:3 sources, which works fine, but always from dubs I made myself.

It seems to me that the only way to fix it would be to resize the image (trial and error I suppose) to match the proportions of the other frame as it seems to be in some non-standard resolution, and then superimpose that into a 720x480 frame, but I'm not sure how I would even go about doing that. Perhaps I am missing something though.

[lordsmurf]

I'd open both videos in VirtualDub, copy frame to clipboard, paste both in Photoshop. Transparency one layer, free transform width until it matches. Hide other layer. Measure dead pixels. Go back to VirtualDub, resize and matte, re-encode. Easy enough. I've done this before a few times.

[dphirschler]

I believe 352x480 is more similar to 704x480. So to match it to 720x480 footage, you may have to size to 704x480 and then pad it with 16 pixels.

You can also play with it in Avisynth. Use a script similar to this and tweak it until v1 matches v2. The values 'a' and 'b' relate to positioning; values 'c' and 'd' relate to horizontal size.

v1=avisource("myvideo1.avi")# 352x480
v2=avisource("myvideo2.avi")# 720x480

# a+b must equal 16
a=8
b=8

v1=v1.pointResize(704,480).addborders(a,0,b,0)# now it's 720x480

w=width(v2)
h=height(v2)

c=0
d=0

v1=v1.crop(c,0,w-(c+d),h).spline36Resize(w,h)
v=v1+v2

return v

View it in Virtualdub to see the changes.


Darryl

[robjv1]

Thanks again you guys, both of your suggestions worked like a charm!