gst_video_time_code_to_date_time() simply calculated the date time based on
adding the hours/minutes/seconds to the daily jam. This causes a gap every full
minute (except for every 10th minute) with drop-frame timecodes as the first 2
(29.97fps) or 4 (59.94fps) timecodes are skipped (not frames!), e.g. with
29.97fps:
timecode: 12:00:59;28 12:00:59;29 12:01:00;02 12:01:00;03
time : 12:00:59.950 12:00:59.983 12:01:00.017 12:01:00.050
and not
time : 12:00:59.934 12:00:59.968 12:01:00.067 12:01:00.100
|-- gap of 2 frames --|
The correct calculation would be to use gst_video_time_code_nsec_since_daily_jam()
and add that to the daily jam.
Also add a test for this.
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8649>
The drop-frame rules are specified in “SMPTE ST 12-3:2016” and are
consistent with the traditional ones:
“
To minimize fractional time deviation from real time, the first two
super-frame numbers (00 and 01) shall be omitted from the count at the
start of each minute except minutes 00, 10, 20, 30, 40, and 50. Thus the
first eight frame numbers (0 through 7) are omitted from the count at
the start of each minute except minutes 00, 10, 20, 30, 40, and 50.
”
Where “super-frame” is a group of 4 frames for 120 FPS.
Fixes#2797
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5028>
