The Director frame was 1/75 seconds? That’s a curious choice because it’s not divisible by 30 which was the most common playback rate.

Film-to-video transfers used a 3:2 pulldown pattern to render 24fps source footage onto 60Hz interlaced video. The exact same approach works for displaying 30fps content on Director’s 75fps display clock… But it’s hard to believe anyone loved 3:2 pulldown so much, they’d intentionally build it in.

Maybe it’s an artifact of the CRT era. I recall refresh rates in the 70-100Hz range were typical in Mac and Windows desktops before LCDs (60Hz on a tube is too flickery for office work). Perhaps 75Hz was a Mac standard in the early 1990s, and that’s where Director got it from.

Another theory: maybe the Director designers thought that 30fps video on a desktop CD-ROM was not realistic, and that content would be at 15fps max. Which has a nice 5x multiplier to the 75Hz internal clock.