'keyframes' metatag is not part of the standard, it is just
convention to use such kind of metatag information for indexing.
Structure is following, it allows to have it inconsistent:
keyframes:
times (array):
time0 (num)
time1 (num)
time2 (num)
filepositions (array)
position0 (num)
position1 (num)
Signed-off-by: Anton Khirnov <anton@khirnov.net>