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MP4 file format "Edits" Box uses different timescale for media start time #1612

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3CHosler opened this issue Nov 6, 2022 · 1 comment
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@3CHosler
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3CHosler commented Nov 6, 2022

MP4 edit list atoms('moov'/'trak'/'edts'/'elst') contain a table of edits, each with three entries. The entries are, loosely, duration, start, speed.

  • duration is given in movie timescale units(listed in 'moov'/'mvhd')
  • start is given in media timescale units(listed in 'moov'/'trak'/'mdia'/'mdhd')
  • speed is a unitless fixed-point number

I think that mediainfo's --details=1 human-readable output presents start using the same units as duration, as opposed to the timescale given in the track's media header.
The fix for this may require some inconvenient, out-of-order precessing. An alternate solution would be to present this value using some unit like "ticks" instead of converting to seconds.

@JeromeMartinez
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There is PR on the way for fixing that.

@JeromeMartinez JeromeMartinez self-assigned this Nov 7, 2022
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