Can anything undo disproportional "stretch-o-vision"?

[tluxon]

I have several clips recorded from HiDef networks where a full screen (4:3 aspect ratio) image was stretched horizontally into wide screen (16:9 AR), but not at a constant rate. The center 1/3 or more of the frame is almost a true proportion while the sides are disproportionately stretched to fill out to at 16:9 AR.

Is there any way to undo this kind of stretching?

[guns1inger]

Can you post a couple of stills so we can see the extent of the problem and have a play ?

[jagabo]

I've never seen a nonlinear stretch on a broadcast although some HDTVs have it as a display option. I find it very hard to watch. I don't know of any nonlinear de-stretch filters.

[Midzuki]

There is an Avisynth plugin called "SimpleResize" which
can resize non-linearly (and undo the "warped resizing" effect as well,
I suppose):

http://www6.impacthosting.com/trbarry/Warptest2.jpg

http://www6.impacthosting.com/trbarry/warptest.jpg

[tluxon]

Can you post a couple of stills so we can see the extent of the problem and have a play ?

It wasn't easy to find a still that clearly illustrates the issue, but I happened to see something from a TNTHD broadcast of the old movie "Clueless" that illustrates the kind of stretching I'm talking about. Looking at the woman in the picture, you can see how this kind of stretching makes her right shoulder look almost the right proportion, but her left shoulder (to our right) is much longer.

[edDV]

TNT-HD is infamous for this. What they are doing is saving some coin by upscaling 4:3 SD DigiBeta tapes to Stretch-o-Vision pseudo HD 16:9. Normally these tapes would be released for 4:3 DVD. They can get these tapes near free. A true 16:9 HD transfered rental costs much more so they save those for prime time.

Even if you can reverse the stretch back to 4:3, the source is most likely still 720x480. Why bother?

[jagabo]

And it's not clear if AviSynth's SimpleResize() will use the same algorithm to unstretch the frame. So you may be left with some odd nonlinearities after processing.

[dphirschler]

I realize this thread's a year old, but it was useful to me. So I thought I would post some before/after results to prove that this filter works at undoing the non-linear/disproportional stretch.

The line that worked for me was:

v=v.WarpedResize(540,360,1.3,1)

So this filter works and works well! Thanks to Midzuki, who knew the answer.


Darryl

[lordsmurf]

CN is notorious for that -- aggravates a lot of cartoon fans.

[billylee8]

So I'm using WarpedResize(640,480,1.15,0.95) to undo-stretch-o-vision and it works great but the colors are pretty messed up. Don't tell me this only works on uncompressed avi or something...

Help?

---

EDIT: Upon closer inspection, my TV clip that I'm using this on still stretches a bit on the top and bottom... guess I'd better play with the numbers more...

[Gavino]

So I'm using WarpedResize(640,480,1.15,0.95) to undo-stretch-o-vision and it works great but the colors are pretty messed up.

If your clip is interlaced, then any vertical resizing will mess up the colors.