Crop-Filter; Options for "Preserve Aspect Ratio" and "Size Restriction"

[guju]

When there is set a DAR (in video stream or in the container)
it is necessary to leave the aspect ratio of the frames.
For not have to calculate the ratio it would be nice to have
a check option of preserving the ratio.

A restriction for sizes of width and height (as multiple of 2, 8, 16, ...)
would be helpful, as some codecs have that constraints.

It would be nice if these two enhancements would work with
the existing automatic croping too.

[guju]

... and (due to experiences I made ...)

the check option for preserving the ratio should be checked as default.
Unchecking it maybe could give a warning ("If DAR is set in codec or container, changing the ratio ...").

The restriction for the size of dimensions could be simplyfied
by not using a check box but only the multiples (default = 1).

Yes, I admit, electric windows, ... but simple and nice ones, aren't they?