[FFmpeg-user] Why is it possible to set a timecode with 24:00:00:00 and beyond?

[Robert Krüger]

On Wed, Jan 13, 2016 at 12:53 PM, Christoph Gerstbauer <
christophgerstbauer at gmail.com> 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.