You might consider quick-and-dirty solutions for this which just modify the file's media descriptors in order to make playback have the desired shape.
I assume that what you call the "final output" is a .mov file.
You have QuickTime Player 7 if you have FCP 5.
Open the .mov file in QuickTime Player 7.
Window > Show Movie Properties
Video Track > Visual Settings
Deselect Preserve Aspect Ratio
Enter whole numbers in Scale Size that give the desired shape. The ratio of the numbers is what matters.
Close file, saving the changes.
Unfortunately this fix only works when the .mov file is played back with QuickTime Player 7! Other players I tried -- QuickTime Player 10, VLC Player, Blu-ray Player -- ignore the Aspect Ratio descriptor. FCP7 is befuddled by it. (I guess FCP5 likewise.)
A better method is to use QT Edit to edit a different descriptor.
Open the .mov file in QT Edit.
Video > Encoding Attributes
Enter the Pixel Aspect Ratio that gives the desired image Aspect Ratio (considering the pixel count, which you're not changing). The viewer shows the result.
File > Save
This fix works with QuickTime Player 10, VLC Player, and Blu-ray Player. It does not work with QuickTime Player 7 or FCP7. Those two read the Pixel Aspect Ratio descriptor but interpret it incorrectly.
Now you can take the .mov file that has been fixed by the second method and apply the first method to it. With both the descriptors changed the .mov file plays correctly in all four players I tested. FCP7 still can't deal with it.
Dennis Couzin
Berlin, Germany
T