[FFmpeg-user] metadata: 'date' behavior in avi/mp4 vs mkv containers

[Mathieu Malaterre]

Hi there,

I am trying to find the documentation for a specific metadata tag:
'date'. According to the following page:

* https://wiki.multimedia.cx/index.php/FFmpeg_Metadata

ffmpeg has a built-in mechanism for tag: 'title'. I also see that my
ffmpeg version has the same  property for tag 'date' but only for a
round trip mp4 ⇔ avi. This property does not work with an mkv
container.

Is this pure luck that tag 'date' is transferred from avi to mp4 & mp4
to avi ? Should it work the same way for mkv container ?

Thanks for clarification,

For reference:

./ffmpeg -version
ffmpeg version N-100064-g3c92268 Copyright (c) 2000-2020 the FFmpeg developers
built with gcc 8 (Debian 8.3.0-6)
configuration: --prefix=/home/mathieu/ffmpeg_build
--pkg-config-flags=--static
--extra-cflags=-I/home/mathieu/ffmpeg_build/include
--extra-ldflags=-L/home/mathieu/ffmpeg_build/lib
--extra-libs='-lpthread -lm' --bindir=/home/mathieu/bin --enable-gpl
--enable-gnutls --disable-libaom --enable-libass --enable-libfdk-aac
--enable-libfreetype --enable-libmp3lame --enable-libopus
--disable-libsvtav1 --enable-libvorbis --enable-libvpx
--enable-libx264 --enable-libx265 --enable-nonfree
libavutil      56. 61.100 / 56. 61.100
libavcodec     58.113.100 / 58.113.100
libavformat    58. 64.100 / 58. 64.100
libavdevice    58. 11.103 / 58. 11.103
libavfilter     7. 91.100 /  7. 91.100
libswscale      5.  8.100 /  5.  8.100
libswresample   3.  8.100 /  3.  8.100
libpostproc    55.  8.100 / 55.  8.100


-- 
Mathieu