EPUB videos

Hi,
I have couple of questions regarding videos in EPUB file.

1) In windows:
      Using Sigil I tried to embed mp4 files to an EPUB file.
      I am not able to embed the video.

This approach works on MAC.

Can you please advise how I can embed mp4 files to an EPUB file in windows?

2) How can we add captions and audio description  to the embedded video?


Thank you all for you input!!

Thanks,
Siri