The process of altering the size of a video without altering the content of the picture (i.e. without cropping) is commonly referred to as resizing. This can mean that we are either expanding or reducing the size of a given video.
Common reasons for resizing are:
Burn to Video or SuperVideo CD (VCD, SVCD respectively) or another standard that defines the dimensions of the video.
Reduce the number of bits required to encode the video at a given quality.
Increase the quality of the video with the specific bit rate/number of bits available.
Before going into the specifics of VirtualDub, we need to know how to calculate the new dimensions with respect to the aspect ratio of the video and the "divide by 16" rule. Prepare yourself to see a couple of mathematical equations in the following text; I promise, however, to provide shortcuts to make it easier.
Suppose the width and height of our video are w and h respectively. The next step is to find out the aspect ratio and crop any black bars...