how to correctly crop mantaining aspect ratio.

[Pepepaco]

I' like to remove 8 black pixels from left,right and bottom borders from a video clip captured from VHS, but I'd like to maintain correct aspect ratio.

I have captured 720x480, and source has a 4:3 ratio.

AFAIK players take these borders into account when stretching the video back to fit 4:3 ratio.

I have read that I should simply crop the video without resize it, but this will affect the aspec ratio, for example:


1.I draw a 320x320 square into a 640x480 image.
2.then I draw a 8 pixel borders to left,right and bottom in this image.
3.then I stretch this image to 720x480.
4.remove the black borders image now is 704x472 .
5.resize back to 640x480.

after that process the square size change to 329x326 the ratio is 1.009, almost a square, but is not longer a square, the same happen if I remove 8 pixels to the top, the result is not a square. the most accurate conversion I have found is to remove only 4 pixles to the top(losing information) or 12 to to bottom instead of 8.

I wonder whats the best way to do it? are dvd players really taking this black borders into account?

your help is really appreciated.

[manono]

If for DVD, you can leave the black on the left and right alone (or replace it with 'fresh' black if it's not true black). For the bottom you can just mask it, or crop it and then replace it with 4 rows of black pixels on top and 4 on the bottom. However, me, I might do it like this:

Crop(8,0,-8,-8)
LanczosResize(716,480)
AddBorders(2,0,2,0)

That will have exactly the same aspect ratio as the source. Again, assuming it's for DVD. If it's for something else you can just crop it and then set a PAR in the encoder to assure it gets played back correctly. But not all players will honor that PAR value.

[Pepepaco]

If for DVD, you can leave the black on the left and right alone (or replace it with 'fresh' black if it's not true black). For the bottom you can just mask it, or crop it and then replace it with 4 rows of black pixels on top and 4 on the bottom. However, me, I might do it like this:

Crop(8,0,-8,-8)
LanczosResize(716,480)
AddBorders(2,0,2,0)

That will have exactly the same aspect ratio as the source. Again, assuming it's for DVD. If it's for something else you can just crop it and then set a PAR in the encoder to assure it gets played back correctly. But not all players will honor that PAR value.

thank you, that really works!!
regards.

[ConverterCrazy]

Please let me know What editing tool/software was used.

Thanks

[manono]

Please let me know What editing tool/software was used.

AviSynth

[Pepepaco]

To capture I was using VirtualDub,
The crop/resize example I converted it to virtualDub filters,

This reminds me I have not finish editing those videos!.

regards.

[ConverterCrazy]

@manono

@Pepepaco

Thanks.

[jagabo]

Assuming your captured video follows the ITU spec, for DVD you can crop down to 704x480 and make a 4:3 DVD. That will give the correct AR. The ITU spec indicates the inner 704x480 represents the 4:3 DAR. The extra 8 pixels left and right are padding. 704 is a legal width for 4:3 DVD. As for the head switching noise at the bottom, crop it away then add black borders back to 480 lines high.

[manono]

As for the head switching noise at the bottom, crop it away then add black borders back to 480 lines high.

Or just letterbox it away:

Letterbox(0,8)

But I always get rid of it for good with a crop and resize.

[ConverterCrazy]

Thanks.

I think, I'll manage with that much input. However, I was looking for WYSIWYG (What-You-See-Is-What-You-Get) kind of editing tool.

Thank you all for suggestions.

[Cornucopia]

I strongly do NOT recommend the crop + resize because that resize interpolation softens the video and VHS is already soft enough.

Much better to letterbox/overlay.

Scott