Full-screen captioning

During the FCC VPAAC working group 1 discussion, consumers expressed their
desire to see formats support full-screen video captions that do not
overlap with the video shown on the screen. Please see the attached file
for a demonstration of this concept.

Early TV captioning with line 21 captioning required that captions overlap
video content, which has been the status quo since then. However, the
Internet offers unprecedented flexibility, so we no longer need to continue
this practice.

Consumers first noticed that captions were much easier to read on letterbox
or wide-screen movies because the captions are situated in black background
while the video content is shown in the middle of the screen. This is our
opportunity to build better captions for the future.

I would like to see HTML5 captions support this feature.