One problem that you'll encounter isn't just the dimensions but more the pixel aspect ratio.

Computers use a 1:1 pixel aspect ratio.  Standard TV is 4:3 and High-Definition TV is 16:9.  This is the x:y pixel size - that is, on a computer, pixels are square whereas on TV they are some rectangle.  I don't think Poser's renderer can compensate for aspect ratio.  "Constrain Aspect Ratio" only pertains to the render dimension not the pixels.

On the actual dimensions,  you'll need to determine the target audience.  NTSC (US) and PAL (Europe) standards use different screen dimensions.

C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, you blow your whole leg off.

 -- Bjarne Stroustrup

Contact Me | Kuroyume's DevelopmentZone