This Wiki page is edited by participants of the HTML Accessibility Task Force. It does not necessarily represent consensus and it may have incorrect information or information that is not supported by other Task Force participants, WAI, or W3C. It may also have some very useful information.
Post examples of accessible HTML5 media (sign language translation, extended audio description) to test and identify shortcomings (talk to the web and TV IG and WEb and Broadcasting IG. Both of those groups have real experience in doing this and shipping this in code.)