transfer mode in quicktime

I am trying to alter a text track in quicktime player with the transfer mode specifier with

set test1 to (choose file with prompt "select test file")
tell application "QuickTime Player"

open test1

set transfer mode of track "Text Track" of front document to transparent

end tell

When I try to compile I get a syntax error

A identifier can’t go after this identifier.
and it highlights the “transfer mode” part of the script

below is from the dictionary for QT

transfer mode (transfer mode unknown/dither copy/no dither copy/blend/transparent/straight alpha/premul white alpha/premul black alpha/straight alpha blend/composition) : the transfer mode of the track

any hits on where I am going wrong?


transfer mode belongs to QT Player 7, the AppleScript dictionary of QT Player X is quite reduced

tell application "QuickTime Player 7"