crop and resize question?

[beav]

If i crop the left and right side of my video by 4, should I add borders and then resize. or should I just resize to 720 by 540 square pixels right after the crop. Does it make a difference?

[Selur]

Sure it does, it will add distortion to the image, if it's too much distortion to bother you are not is your decision

[beav]

So it would be best to add the borders and then resize to 720 by 540 square pixels correct? In order to avoid disortion?

[Selur]

yes.

[beav]

Thanks Selur!

[hello_hello]

Are you referring to cropping and resizing a 4:3 DVD to 720x540 square pixels? If so it's not necessarily a simple answer as there's more than one way to resize a DVD. Either way I'd probably not add borders to replace the cropped video, I'd probably crop a little from the height as well to stop the picture from being distorted when it's resized that way.
Without knowing exactly what you're doing, have a play with this resize calculator (it's an exe but it's perfectly safe): http://www.mediafire.com/download/09v9bldu9a6hm00/YodaResizeCalculator.exe

Select the appropriate video input type/dimensions, add your cropping, adjust the resizing etc and the calculator will calculate the aspect ratio distortion for you. The idea being to then adjust the cropping and/or resizing as necessary to keep it at a minimum.

When you select a DVD as the input video, the calculator gives you the option of using ITU-R BT-601 coefficients. As you'll see when you check or uncheck that option, it changes the way a DVD is resized a little, which effects the way you'd crop and resize it. Without getting into a DVD resizing discussion, my rule of thumb is this:

If a DVD requires a lot of cropping each side (around 12 or more pixels) it's likely to use ITU resizing. If it requires very little cropping it probably doesn't. A 4:3 DVD is fairly likely to use ITU resizing. Most 16:9 DVDs don't (unless they're pretty old).

[beav]

Thanks hello_hello! I cropped 4 off the left and right side of my video and successfully resized correctly to 720 by 544 square pixels. 720 by 540 was the incorrect way to resize.

[hello_hello]

If you're resizing a 4:3 DVD without using ITU then you could also crop 4 pixels from the height and resize to 720x 540. That'd distort the picture slightly less and also give you an exact 4:3 output aspect ratio, but which way you do it is really personal preference. When resizing I aim for an exact 4:3 or 16:9 output aspect ratio if I'm already close after cropping, but each to their own.....