Am 13.01.2016 um 22:30 schrieb Dave Rice:
On Jan 13, 2016, at 9:25 AM, Bouke / VideoToolShed <[email protected]>
wrote:
On Jan 13, 2016, at 14:17, Robert Krüger <[email protected]> wrote:
On Wed, Jan 13, 2016 at 12:53 PM, Christoph Gerstbauer <
[email protected]> wrote:
FFmpeg allows me to set a timecode of 24:00:00:00 and beyond.
e.g "-timecode 24:00:00:00"
When I make an MXF D10 for example, the value of 24:00:00:00 is still in
the file.
Most but not all programs ignore this and display 00:00:00:00 correctly.
Here are some sample extractions of the timecode offset value in different
mxf d10 files generated by ffmpeg:
PAL 25fps:
-timecode 12:34:56:11 -> in file: 11477b hex -> 1132411 dec
-timecode 10:00:00:00 -> in file: 0dbba0 hex -> 900000 dec
-timecode 20:00:00:00 -> in file: 1b7740 hex -> 1800000 dec
-timecode 23:59:59:24 -> in file: 20f57f hex -> 2159999 dec
-timecode 24:00:00:00 -> in file: 20f580 hex -> 2160000 dec -> 24h
-timecode 24:00:00:01 -> in file: 20f581 hex -> 2160001 dec
-timecode 25:00:00:00 -> in file: 225510 hex -> 2250000 dec -> 25h
NTSC 30fps
-timecode 23:59:59;29 -> in file: 2782df hex -> 2589407 dec
-timecode 24:00:00;00 -> in file: 2782e0 hex -> 2589408 dec
Why is this possible to set a timecode after 23:59:59:XX?
Is there a usecase?
I wasn't able to find any official spec that says what the limit for the
hour part is but since it in the general case does not define a time of day
but an offset, why limit it to 25 hours and not use the full 100? On a
side-note, I have not come across a real-world use case for a timecode of
that magnitude either.
Some forms of TC just lack the space to store higher numbers IIRC (LTC / VITC,
perhaps also in MpegII frame headers)
But there is logic in not going higher, as it is ‘time’.
For a real world use case, in the old days of tape, a reelname most of the time
corresponded with the hour.
So a production with more than 24 tapes needed better administration in reel
names that had to be written on the tape and box.
FWIW QuickTime timecode flags includes a "24 hour max" flag to clarify when it is and is
not enabled in a timecode track, but >24 hour values are certainly allowed in the QuickTime
spec. https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html
<https://developer.apple.com/library/mac/documentation/QuickTime/QTFF/QTFFChap3/qtff3.html>
Dave Rice
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Hello Dave,
as seen in SMPTE S012M Time and Control Code from 1999:
Page 2 of 21 pages:
"4.2 Time address of a frame
Each frame shall be identified by a unique and complete
address consisting of an hour, minute, second,
and frame number. Refer to ANSI/SMPTE 258M for
standard formats used to display frame-based time.
The hours, minutes, and seconds follow the ascending
progression of a 24-hour clock beginning with 0
hours, 0 minutes, and 0 seconds to 23 hours, 59
minutes, and 59 seconds. "
It would be interesting what would be mentioned in the newest SMPTE
version about timecode.
Does anyone have this standard paper? (Year 2014)
Best Regards
Christoph
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