[FFmpegMetadata] Store release_year in the metadata

[unkernet]

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Description of your pull request and other information

Many music extractors returns only release_year field, and it is not stored in the metadata.

[dirkf]

According to https://kodi.wiki/view/Video_file_tagging as quoted in the source, ffmpeg knows of a year metadata item. Wouldn't that be a more appropriate place for this, seeing that release_year is rather broad as date? But then the next source says that no such item exists ...

[unkernet]

The correct field is date, not year.

Lets add both and check with the iTunes.

% ffmpeg -i 1.mp3 -codec copy -metadata year=2021 -metadata date=2022 2.mp3
% ffmpeg -i 2.mp3 -f ffmetadata 2.txt
% cat 2.txt
;FFMETADATA1
title=Grow in Japan
artist=Geju
album=Sad Elements
genre=electronics
track=1
album_artist=Geju
disc=1
date=2022
composer=Leveldva
year=2021

[dirkf]

This will set a year rather than the yyyymmdd value if both items are available. Shouldn't they be reversed?

[unkernet]

I think not. This field called "Year" in most media players.

[dirkf]

The add() function above could be improved based on yt-dlp (import T(), traverse_obj(), txt_or_none(), variadic() from ..utils):

        def add(meta_list, info_list=None):
            if not meta_list:
                return
            meta_list = variadic(meta_list)
            info_list = variadic(info_list) if info_list else meta_list
            value = traverse_obj(info, (info_list, T(txt_or_none), any))
            if value not in (None, ''):
                value = value.replace('\0', '') # nul character cannot be passed in command line
                metadata.update((meta_f, value) for meta_f in meta_list)