Re: [FFmpeg-devel] [PATCH] avformat/mov: remove hack breaking creation time parsing

[Marton Balint <cus@passwd.hu>]

On Tue, 11 Apr 2023, Bernd Dürrer wrote:

> On Sun Apr 9 20:20:04 EEST 2023, Michael Niedermayer wrote: 
>
>> what do you mean by intended creation time?
>> the file format did not exist in 1946. and all the codecs also didnt exist
>> so when you encounter a file that says its from that time it must be crafted
>> later and backdated or that bug.
>
> As defined in ISO/IEC 14496-12, clause 8.2, "creation_time is an integer 
> that declares the creation time of the presentation (in seconds since 
> midnight, Jan. 1, 1904, in UTC time)". This is the date when the content 
> was created (which may have been on photographic film), and not when it 
> was encoded as a digital file.

I don't think that is true, it is not clear from the specs at best. The 
creation time of the presentation can just as easily refer to the file 
itself, not the content. Feel free to reencode something with a commercial 
encoder, I would be suprised if creation time was kept.

I think the proper metadata for the creation time in the sense you want it 
to be is com.apple.quicktime.creationdate, here is an example with 
different moov creation time and com.apple.quicktime.creationdate.

https://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket5120/incorrect-start-frame.mov

Maybe you can check if the DLNA server reads that. Or if it only reads the 
year information, then com.apple.quicktime.year might be even better.

https://developer.apple.com/library/archive/documentation/QuickTime/QTFF/Metadata/Metadata.html

Regards,
Marton
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