The recognized time attributes include any per-vertex time for a line
or the following attributes:
Hour - 'TIMECODE (H)'
Minute - 'TIMECODE (M)'
Second - 'TIMECODE (S)'
Frame - 'TIMECODE (F)' .
The beginning time of the video is determined from the earliest time
in the file and that is subtracted away to get the video-relative time.
A single TIMECODE attribute in the format 'HH:MM:SS' or 'HH:MM:SS:FF'
is also supported.
Absolute date/time values in attributes TIMESTAMP, UTCDATE/UTCTIME, or TIME. If any of those are present with a recognized time format they are used as the absolute time and the earliest recognized time in the file is treated as the time for the video start.