House has studied the "event timeline" for a large number of pitchers. He calls the start of leg lift t = 0 and then gives average times to some other events in the pitching moption.
Thus, he suggests that the time from start of leg lift to footstrike is between 0.95 to 1.05 sec for most pitchers.
I think he has 1.25 sec as an average time to ball release on his timeline.
At 30 fps, that's about 30 frames of video from beginning of leg lift to footstrike and 37 or 38 frames from beginning of leg lift to release.
Some caveats: The first interval is difficult to judge with great precision because the exact "beginning" of leg lift is often relatively subtle and hard to pinpoint. Another issue is the second interval, from footstrike to ball release. Both of these events can be pinpointed in high-speed video with good precision so the numbers should be pretty good. However, House's numbers suggest about 0.25 sec between footstrike and ball release--this number seems too long by about 0.1 sec to me.