Windows 10 22H2
1. Does XnView MP capture only keyframes (i-frames) of a video?
This question has been asked before: viewtopic.php?f=62&t=46673
A similar problem occurred to me, thumbnails was repeated, I speculate that this problem may be caused by XnView MP only capturing keyframes (i-frames). Although capturing only i-frames makes the process faster, sometimes we want to capture arbitrary frames and it is recommended to add an option to capture arbitrary frames.
2. When Spacing is set to 0 in the “Create Video Gallery” window, the image created has a black edge on the right side.
See below, I create two 2*2 thumbnails:
With spacing set to 0, half of the image is black and only two thumbnails are captured.
With spacing set to 1, the image is correct.
spacing set to 0 ↓
Thanks to your detailed description I can reproduce