test the case of "reading video file in exported folder", it work.
You can try by these steps.
1. download test file (movie.ogg) from gonzdevour's link
2. in capx, assign src url to "movie.ogg", then export capx.
3. put movie.ogg downloaded (at step1) into export folder (at step2)
4. open the index.html in exported folder. It works in my testing.
You can also put it in a video folder by entering:
2b. in capx, assign src url to "video/movie.ogg", then export capx.
Then just make a folder named video and put that with all movies into your export folder.