I spoke on Adobe’s efforts to support the captioning aspects of the 21st Century Communications and Video Accessibility Act at the TDI Conference a couple of weeks ago in Austin, TX. In this talk I highlight a number of efforts to support captioning that Adobe has worked on – most people interested in captioning are familiar with some but not all of these. Take a look and let me know if you have any comments.
Presentation: Supporting the CVAA with Captioning for Video and Live Meetings.

Is it known yet what the deadline is for delivery of closed captioning and video descriptions for video displayed online?
Thank you.
No, not yet. The VPAAC committee submits its recommendations to the FCC on July 13.
I understand that cc is not supported in mp4 publishing. Is that true??
No. MP4 files can be captioned.