Describe the problem precisely
VLC's video controls distinguish aspect ratio, crop and zoom. Before changing one, decide whether the concern is the shape of objects, unwanted edges or the size of the viewing area. Those are different observations and should not be treated as one generic picture fix.
Compare against an unchanged reference
Use an authorised sample with a recognisable shape, such as a circular object or a title card you created. Preserve the initial player state. A crop can hide edges while losing picture content; changing proportions can alter shapes. Compare one control at a time.
Do not infer the correct source geometry simply because the screen becomes full. A presentation that fills the window can still distort the image or conceal useful text. No visual comparison was performed for this article.
Keep playback and export distinct
Record the selected viewing control and return to the baseline before opening an unrelated sample. A player-side change does not establish a corrected source file. If a portable corrected master is needed, define and verify that separate editing or encoding task.
Questions answered
Does filling the screen prove the proportions are correct?
No. Check recognisable shapes and whether useful content was removed.
Does changing VLC's viewing control rewrite the source?
Do not treat a playback-view adjustment as a new edited or exported file.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.