Q: Is there a simple way to "upconvert" SD video to HD in iMovie or FCP?

Is it 4:3 or 16:9? Don't know about iMovie but you can do it FCP or in Compressor if you don't need to edit as well.

Create a new project, set its dimensions and frame rate specifically. DON'T let it be set by "first clip", or it will become an SD project.

Drag your movie to the timeline. By default, the Spatial Conform parameter in the Inspector is set to "Fit" and this will enlarge your clip to match the size of the project.

(both being 16:9, there will be no black bars; otherwise you might leave it pillarboxed or change to Fill, in which case a small amount of content at top and bottom would get out of the frame).

Robert Lawton wrote:

 

Thanks.

Then what?

File->Share->Master File; under Settings, choose H264. Upload via the website.