To edit video metadata without re-encoding a video, you can:
- if the video is an mp4 use VLC (tools/media info), with many options (besides title and date, you can set genre, artist, album, comment and so on).
- if the video is an mkv use MkvToolNix Header editor (only for title and date)
Unfortunalely, MkvToolNix is not able to change other than title and date.
But a workaround can be
- convert a video from mkv to mp4 (copying audio and video: very fast)
- edit the new mp4 metadata file with vlc
- re-convert (if you want) the mp4 file to a mkv file (copying audio and video), keeping your added metadata.
I found that a good tool to make the conversion (from e to mkv, editing the preset and selecting copy audio and copy video, in audio and video tabs) can be MistiQ Video Converter.