Feature Request: Cover thumbnail from time code for MP4

For episodes of TV shows using MP4 tags, it would be particularly useful to be able to select a time code (either absolute, e. g. at 30s, or relative, e. g. 10% of runtime) from which the frame would be used as a thumbnail picture since cover images are usually not available.

Kodi uses video tags and hence embedded graphics since the latest major release, v18 Leia.

Quicktime MOV apparently supports tags to specify the time code for preview images (poster) and clips, i. e. there is no need to actually embed an image that is already available as a frame. This info is stored in mvhd inside moov. Iʼm not sure whether that is possible in MP4 as well, or supported by players and media centers.

  • Preview time
    The time value in the movie at which the preview begins.
  • Preview duration
    The duration of the movie preview in movie time scale units.
  • Poster time
    The time value of the time of the movie poster.

Usually, Mp3tag does not deal with anything else but the tag data - so there is no analysis of the stream data.
AFAIK VLC can take snapshots from video files which then in return can be embedded as covers by MP3tag.

Extracting an image and converting it to PNG or JPEG for storage inside the tag would indeed require parsing the video data, but just setting the time index would not.

Which field would be used for this information?
Did you have a look at a file and check the extended tags dialogue? I don't think that there is a standard field, so it would be a user-defined one.
Or do the players store this kind of information in their own database and not in the tags?

Poster time, please see the Apple Developer documentation I linked to above. Itʼs part of mvhd, not udta like textual info tags.

If I understood correctly... You could use FFmpeg to specifically batch extract frame images from many movie files, by specifying the time. Then you could use Mp3tag to put them in. For the Matroska container, those extracted images could be then batch embedded with MKVToolNix.

Yes, I know I could (and would have to) use other tools to actually extract frames from a video track, but I would prefer to only specify a poster time index anyway.

Apparently, the MP4 format does not support time-based thumbnails, but HEIF does.

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