thank you for your suggestion.
Please note that, by default, the registry did not exist.
I added the registry, and I tried with the value 18 and 24 (then also with 48 and 96) but in all the tests the behavior was always the same.
There is also a "VideoMemSize" register, with value dword 6291456. Can you try something here too?
I also tried changing the videos, turning them into 480 * 272 reducing the bitrate a lot, but nothing has changed yet.
I also tried removing the full screen, but nothing has changed.
When I first open the form which then launches the video, it doesn't start. But if I close and reopen the same form immediately afterwards, the video always started.
EDIT: By carrying out further tests it is not 100% sure that the second opening of the form the video will start. However, there is a good chance that it will start correctly (about 70%).
Perhaps, by solving this thing of the first opening of the form, we can reach a compromise.
But I don't know what can affect this? The form performs the same operations when it is opened the first time and also the second time.
Probably some "hidden operation" of the OS at the first opening of the form?