Is there a word/phrase for the reciprocal of frame rate?

Frame rate is to frequency as ____ is to period?

If a video has a frame rate of 25 fps, the video has a 40ms ____?

2 Answers

Frame duration?

This quick Google Search gives quite a few people who are using it in support questions for video editing, and here is a definition on the website for the Institute for Telecommunication Services:

frame duration: The time between the beginning of a frame and the end of that frame. Note: For fixed-length frames, at a fixed data rate, frame duration is constant.

• "Frame duration" is an example of a compound noun. Compound nouns are permitted in English but they can make your writing seem cold and technical, and even confusing. I was going to suggest "duration of each frame": "... the duration of each frame {in the video} is 40 ms." Commented Aug 15, 2019 at 10:19
• Thanks, I actually end up using interval in my situation. But I think because of the way I describe the question, especially the example, frame duration may be more accurate here and I'm going to accept it as the answer. Commented Aug 20, 2019 at 1:58
• @whiskeychief But frame rate is a compound noun too, no? Commented Aug 20, 2019 at 1:59

The normal use (at least in my experience, I have a technical/scientific background) is to say the interval as the elapsed time between events that happen with a known frequency. So if interval is the reciprocal of rate then we might think that frame interval is the reciprocal of frame rate.

However in regards to video, this does not appear to be in common usage. Typical video encoding techniques do not encode complete frames of video, only partial frames are encoded (to reduce the size of the video data). The distance betyween the full frames is normally known as an interval - either the Key Frame interval of the I Frame interval depending on the encoding sceheme, software tools and audience.

Key frames Explained in Wikipedia

Mention of "Frame Interval Timing" which is relevant to a particular manufacturer of cameras.

Great Question!