Hi Mary,
Thank you for checking. I wanted to write to you in detail. Earlier you've sent me a short project with one sample video object.
I see this problem: preview doesn't show doubled video speed when you set the speed to 200% (i.e., 2x acceleration).
The problem is that the video file is too large - 4K resolution (3840 x 2160), 60 fps.
PTE AV Studio can't play it at doubled speed, sorry! Only when exporting a MP4 video.
I see a possible solution: professional video editors usually create a simplified copy of the video at a lower resolution and use it for previews. PTE AV Studio currently always works with original video files. We probably need to consider a similar solution.