Can I have a video with transparent background using HTML5 video tag?

Question

We filmed a spokesperson on a green screen and have the video files ready in multiple formats.

With Flash we could use the wmode transparent within the param and em

Answer 1

At this time, the only video codec that truly supports an alpha channel is VP8, which Flash uses. MP4 would probably support it if the video was exported as an image sequence, but I'm fairly certain Ogg video files have no support whatsoever for an alpha channel. This might be one of those rare instances where sticking with Flash would serve you better.