Custom thumbnails for videos not displaying

[zzb226]

viewtopic.php?p=175477
Same problem as described in the above URL,the problem still exists in version 1.4.0.
I turn on "Use embadded thumbnails" and make a video with an embedded thumbnail,but Custom thumbnails for videos not displaying.

[xnview]

for mp4? Try to start it from terminal, and use 'Rebuild thumbnails' on the video file, what do you have as debug information?