Instantaneous metadata cues

If you try to represent an instantaneous metadata event with eg. "00:0.050
--> 00:0.051", the metadata cue (and more importantly, its enter and
cuechange events) may never be fired, since the current playback position
may never lie within the cue.  Worse, that particular cue would probably
work reliably for a 25 FPS video (a frame begins at 50ms), but break if the
video track is replaced with a 30 FPS one (a frame begins at 33ms).  That
means changing the framerate of a video could affect scripts.

It would be ideal if cues were always entered and exited, even if the
current playback position skips over the metadata's time range.  (During
normal playback, that is, not if the user seeked past it, or if the UA had
to discard cues for performance reasons.)

-- 
Glenn Maynard