Uhh, the Captivate plays 720i videos. (HD). The screen resolution of the Captivate is 480 x 800 and that has nothing to do with HD videos.
So yes, you want to use the 720i because 480i is nearly standard def.
Last time I checked (and I work in the biz), there is no 720i standard. 720p is considered HD video. 480i
is standard def, no question about it.
The numbers you see are horizontal lines of picture resolution. A standard definition screen is typically 720 pixels
wide by 480 pixels
high. Even though the width of a screen is considered its
horizontal size, the term "horizontal resolution" is a misnomer, because it actually measures how many
horizontal lines (side-to-side) are stacked up
vertically (top to bottom). It should be called
vertical resolution, but the fine folks who came up with the NTSC standard did so on "backwards day."
A high-definition picture can either be 1920 wide x 1080 high (where the 1080 refers to the height of the screen in pixels, thus "horizontal" resolution - get it?) or 1280 x 720. The 1280 x 720 video will play fine on the Captivate (even though the 720 pixel
height of the video is taller than the 480
width (in portrait mode) of the Captivate screen). Why? Don't ask me, but I believe (at least when discussing the MX Video Player app that I use) that some downscaling takes place to fit the 720p picture inside the 800 x 480 screen.
Oddly enough, widescreen SD is 868 x 486, but these, too, play fine on the Cappy's screen (assuming downscaling is taking place). MX Video Player apparently has some pretty robust algorithms being used for downscaling, because I rarely see any artifacts related to shrinking down the video to fit the screen. (Notice I use the word "downscaling," not "downconverting." Downconverting a video would involve re-encoding, and I don't believe MX Video Player is capable of doing that on the fly. Nothing I've worked with to date will do so. There's lots of computing horsepower involved.)
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