If you need to display a 720x486 image, then you can pre-allocate a 1024x512 image using TexImage2D, and then use TexSubImage2D to update only the lower-left corner 720x486 pixels per frame.
Note that your U/V range then goes from 0 to 720/1024 and 0 to 486/512, with a black band outside it. And, if you use interpolation, 0 really is in the center of the outermost pixel and the texture border/color, so you’ll want to inset these coordinates by the width/height of half a texel.