Well, i had fun making the OpenGL app anyway

I can see the triangles skew up well when shape is heavily starting to stray from rectangle. Next thing to try would propably be adding 1 vertex to the middle, and draw 4 triangles. Still not sure that would fix it.
Anyway, see "Perspective mapping" in already linked:
http://wiki.lazarus.freepascal.org/BGRABitmap_tutorial_10Also know that 1080p (1920 x 1080) FullHD video is highest that for example youtube will let you upload. This is 2 Mp.