Help with looping films please!

Hi, I'm an artist and want to work out how to synchronise 3 looped films with different durations.

For example, Film 1 is 100 frames long, Film 2 is 150 frames long, and Film 3 is 200 frames long. If they start playing at the same time, the point at which they synchronise is at 600 frames, when they have looped 6, 4 and 3 times respectively.

So far so simple. But the films I have don't have simple durations - one might have 183 frames, another 5669 frames, etc. How can I calculate when they will synchronise?

Any help will be gratefully received; I'll even send you a link to the finished artwork!

Re: Help with looping films please!

Quote:

Originally Posted by

**yearling** Hi, I'm an artist and want to work out how to synchronise 3 looped films with different durations.

For example, Film 1 is 100 frames long, Film 2 is 150 frames long, and Film 3 is 200 frames long. If they start playing at the same time, the point at which they synchronise is at 600 frames, when they have looped 6, 4 and 3 times respectively.

So far so simple. But the films I have don't have simple durations - one might have 183 frames, another 5669 frames, etc. How can I calculate when they will synchronise?

Any help will be gratefully received; I'll even send you a link to the finished artwork!

You want to find the Lowest Common Denominator of the films. You did this in your first example by finding the LCD of 100,150 and 200 which is 600.

Prime factors are the simplest way to find out LCDs so if we split 100, 150 and 200 into it's prime factors we get:

$\displaystyle 100 = 2^2 \cdot 5^2$

$\displaystyle 150 = 2 \cdot 3 \cdot 5^2$

$\displaystyle 200 = 2^3 \cdot 5^2$

To find the LCD multiply the highest powers of each number. In this case $\displaystyle 5^2 \cdot 3 \cdot 2^3 = 600$

The prime factors of 183 and 5669 are:

183: $\displaystyle 3 \cdot 61$

5669: $\displaystyle 5669$ (5669 is prime)

Can you work out the LCD?

Re: Help with looping films please!

Thanks for your quick reply!

3 x 61 x 5669 = 1037427

That's so helpful! I would never have worked it out by myself.

Thanks again.

Re: Help with looping films please!

Quote:

Originally Posted by

**yearling** Thanks for your quick reply!

3 x 61 x 5669 = 1037427

That's so helpful! I would never have worked it out by myself.

Thanks again.

Yep, thats the one. That is the total number of loops though so if you need to find out how many times *each* film looped divide it by the number of loops in the film. Hence your 183 frame film will loop 5669 times.

Re: Help with looping films please!

extra tip: if you want a loop that simulates "an ever-changing interaction", make sure your loops are "medium large" prime numbers. if, on the other hand, a shorter period is desired, choose loop lengths that have a lot of common factors (synchronized to the longest loop, for example) (a number like 120 has a lot of different factors, for example). hopefully you can control this by choosing the frame number of the loops through careful editing.