@EpheMeroN
A video can only have one resolution. If you want the output resolution to match the second part of the video, you will need to scale the first part down by a lot (or crop a lot, which would leave very little of the original content). Try:
Code:
FFMpegSource2("VIDEO0007.mp4",atrack=-1)
# 480 / (800/480) = 288
# (800 - 288) / 2 = 256
Trim(0,729).BilinearResize(288,480).AddBorders(256,0,256,0) ++ Trim(730,1543).TurnLeft()