Selur's Little Message Board

i was pretty sure this is how works  CROP and LETTERBOX... for example remove top/bottom noise of a VHS and make final output as the same resolution of original... right?

i placed 2 clips (one cropped+letterbox and one not) side to side and using my eyes seems there are not differences ... i'm correct?
there is no resizes involed if i use letterbox to reach the same resolution of original clip...

i 'm a lot worried about losing details.. just this. (talking again about PAL 720x576)

According to what I see, you take a source which is: 720x576, then crop it to 720x576 and then add the cropped off parts back to get 720x588.
I assume this is what you wanted.
To compare it, you can simply co to the Filtering-tab, enable 'Compare view' and look at the Vapoursynth/Avisynth preview.

Cu Selur

yes it is, and i also compare the 2 views using this method, btw i assume there are no changes (of any kind) to original footage (a part the 2 black bars)
thank you

You can look at the Vapoursynth Script to see what is happening.