How to remove letterbox/pillarbox bands

To remove the horizontal black bands of the letterbox or the vertical black bands of the pillarbox we need to change the size and aspect ratio of the source by cropping.
For example, if we want to remove the letterbox from a 4:3 frame to leave only the content with aspect ratio 3:2, we can act on the project format by doing the following steps:

1- Check the size of the base W of the original frame in pixels; e.g., W = 768 px
2- Obtain the height of the figure in 3:2, i.e., without the black bands; H can be obtained from the formula 3/2 = W/H, from which H = (768 x 2)/3; e.g., H = 512 px
3- Note that WxH = 768 x 512 is just the crop we are looking for to switch from 4:3 frame to 3:2 frame without letterbox
4- Open Set Format window: Settings --> Format
5- Change H to 512 and set Display Aspect Ratio to 3:2; press Apply and OK. Note that we leave W unchanged, since the frame width does not change.
6- If needed, act on the Camera tool to get the desired viewport.

Note: in complex situations, with multiple sources of different sizes, it may be appropriate to premise an additional step to the second: change the size of the track on the timeline via RMB --> Resize track.
In this way we crop the track to match it to the project format that we will change in the next step. This way we avoid possible unwanted distortions.

In the case of the pillarbox, we will leave H unchanged while calculating the new value of W. The formula x/y = W/H is valid for any aspect ratio (4:3; 16:9; 2.35:1; etc)