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.
Media Multitrack Media Rendering
Collection of different display approaches to multitrack video
from http://greenbd.info/CourtneyWoolsey/
Four video tracks displayed in tiled fashion within one viewport.
from http://cache.gawker.com/assets/images/gizmodo/2009/04/mlbtv_02.jpg
Example of picture-in-picture rendering of a second track/video.
from http://www.westmidlandsprepared.gov.uk/2007/05/07/fire-website-for-the-deaf-a-first-in-the-country/
Example of a video on left with synchronized sign language video on right.
from http://www.tvworthwatching.com/werts/2008/08/
Four video tracks displayed in sync where first one has a large representation and the other three are tiled down the right.
from http://www.shootfortheedit.com/forum/showthread.php?407
Synchronized picture-in-picture display of a second video track (video commentary).
from http://advocacine.wordpress.com/category/notes/page/4/
Synchronized picture-in-picture display of a sign language second video tracks.
Synchronized picture-in-picture display of a sign language second video tracks.
from http://world-sat.info/showthread.php?t=65764
Seven parallel video tracks displayed with six overlayed as pip on top of the first.
from http://www.bbc.co.uk/iplayer/
Sign language video green-screened on top of the main video.
from http://www.flickr.com/photos/bsktcase/49152259/
Sign language video green-screened on top of the main video.
from http://www.flickr.com/photos/58285552@N00/41384817
Sign language video blended on top of the main video.
from http://mlb.mlb.com/images/2009/10/06/ZyoQHHvu.jpg
Four synchronized video streams displayed in tiled form (different camera views).
from http://gigaom.com/video/att-lets-cubs-fans-choose-their-own-camera-angle/
Multiple video tracks for different synchronized camera view displayed with one main video and a scrollable number of others on the side.
and 
from http://www.sportsgeekery.com/2010/10/28/watch-tnts-nba-games-online-with-overtime-extra/
Tiled display of four different camera views of a synchronized video, and pip view of a different player in an overlay in time-sync.
from http://hardgeek.org/youtube-doubler (orig: http://youtubedoubler.com/)
Two different videos loosely synchronized for mash-up purposes.