v26 - missing thumbnails of folders with video files

[masterjp]

I have a folder with some video files. In albums view I do not see a thumbnail on the video folder.
I hope to see at least a single picture of the first video file.

[xnview]

which format? i have a folder with a mp4, and there is the thumbnail in album view

[masterjp]

I tested my mp4 and mkv video files again. Most of them have a resolution of max. 1920 x 1080 pixels (h264 or h265 video track) with AAC audio track.

On my small smartphone display the thumbnail of the video folder was black.
On tablet I tested it again and saw a thumbnail on the folder of my video folder.

The thumbnail is created by xnview. I am not sure, which file is used.
In my folder I see a thumbnail of file no 5. It could the first file which was saved in the folder.

Maybe it is better to choose a frame of the video file at position 0:05 instead of 0:00, because it often could be black.