Pixel iteration when footage smaller than sequence size?

Hi everyone,

I am having a problem with my plugins when the footage is smaller than the sequence.

For some reason Premiere (and only Premiere, AE is fine in this regard) iterates pixels not from the clip origin (let's say 200,100), but from sequence origin (0,0). Since it only iterates the amount of pixels that is proper clip size (correct), it results in part of the layer being totally cut off (in this example 200 pixels from the right, and 100 pixels from below).

For what it's worth, if the clip has proper aspect ratio, and scale to sequence size is clicked, or if the bigger clip is scaled down, the effect is applied properly.

I have tried using various offsets, but I could not get it to work. Obviously I'm missing something. I am using AE SDK.

Thanks for any help.

Bart