About OpenMax AL

Hello :
I have a problem about OpenMax AL, please help me, thanks!
XADisplayRegionItf->SetRegion(XADisplayRegionItf self, XAint16 top, XAint16 bottom, XAint16 left, XAint16 right). The top left corner of the display is (0, 0). A negative values indicates a position off-screen or partially off-screen. Video or image content scales to fit specified display region.
IF the video size of 720X480, set up display region - of size 320x240. The video resizes display partially video by cropping or display complete video by compression??? and AL norm whether allow display partially video by cropping??