yoffset in SPUMUX not working?
 

I use the formula

464-{height of the subtitle .png}

to determine the y-offset in SPUMUX for variable size subtitle .png images when authoring NTSC DVD. A margin of 16 pixels is there already for the overscan area. But it always ends up that part of the subtitle still fall within the overscan area on TV. The x-offset works as expected but it seems that y-offset is ignored.

Does anyone know whether it is a known bug in SPUMUX or y-offset has a different interpretation than x-offset.

Thanks