How to access certain value (scale of transform strip in VSE)


how can I access the value in the red circle in the screen shot? It’s a property of a Transform strip in the VSE.

The value is animated, i.e. there is an F-curve for it, so it’s value changes during animation.
I’ve copied the data path using right-click -> copy data path:[“Video”].sequence_editor.sequences_all[“Transform”].scale_start_x

which syntactically works, but during rendering an animation (Ctrl+F12, NOT Alt+A), the value is constant for all rendered frames. It has the value at the current frame when starting the animation. Maybe that’s what the name “scale_start_x” indicates.

So how can I access the value at the frame to be rendered? (I want to use it in a Driver using a scripted expression)