Well, I wound up recording some footage (which turned out to be a bigger hassle than I thought.
) and tried measuring the distances in each frame (which wasn't exact because my footage was a little blurry.)
After analyzing the numbers, while I didn't get a direct pattern, it was easy enough to extrapolate what the correct pattern is, after granting some tolerances for my inaccurate recording methods.
I'm sharing the results here, in case anyone is is curious, or comes looking for this information in the future.
Quite simply, gravity increases downward velocity by one pixel-per-frame each frame. Jumping seems to add 10 ppf to the velocity, (although collecting data for the initial frame seems to vary). This works out so that the distance traveled in each frame for a standard jump is:
0, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0
which translates to the player's distance from the ground being:
0, 10, 19, 27, 34, 40, 49, 52, 54, 55, 55, 54, 52, 49, 45, 40, 34, 27, 19, 10, 0
Measured to the bottom of the player's foot.
Terminal velocity is 15 pixels per frame, which is reasonable since the collision blocks are 16 pixels, and if an object traveled faster than 16 pixels per frame it would pass through a whole block without being detected. It is likely that no object in the game can ever exceed that speed in any direction.