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I'm searching for a formula which can calculate the remaining video speed if selected different speeds.

So if I have a video and watch it twice as fast, then it's half the time. That's easy. But what should I calculate if I use 1.25, 1.5 or 1.75 times speed?

And how can I use the formula the opposite so when watching with slower speed like 0.25 or 0.5?

Steven2105
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  • twice as fast = half the time. I think you already get the answer, divide by the speed. – zwim Oct 28 '20 at 09:48
  • Hint: if a video has n frames, and the speed is n frames/second, how long does it take to watch all n frames? – DavidW Oct 28 '20 at 09:48
  • @zwim Ah, I see. And how do I calculate a slower speed because if I divide 50 through 0.5, I get 100? – Steven2105 Oct 28 '20 at 09:51

1 Answers1

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$\frac{T_1}{T_2} = \frac{S_2}{S_1}$, where $T_1, T_2$ refer to times (lengths or durations of time) and $S_1, S_2$ refer to speeds of the videos.

Note the reversed ratios, because the speed and time length are inversely proportional.

Example of application: you have a video length 5 min at normal (1x) speed. What is the length (in time) at 1.75x speed?

$\frac{T_1}{T_2} = \frac{S_2}{S_1}$

$\frac{5}{T_2} = \frac{1.75}{1}$

So $T_2 = 2.857...$ minutes, which is approximately $2$ minutes $51$ seconds.

For slower than normal speeds (like 0.5x), just put that in place of $S_2$.

Deepak
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