maths problem, please help!

[theartknife]

Hey guys, i have a maths problem that i'm hoping somebody can help me with. It may seem easy to you guys, but it's 01:51 AM and..... dammit, i went to art school!

Anyways, the backstory here is that i'm a filmmaker and i'm using two different pieces of software to work on a project. I have a pretty solid workflow to get my files from one to the other, but it misses out adjustments that i make to the speed of my video clips in the first program so that when it gets to the second one the clips are no longer in synch.

Now for the part that has got me stuck.

The first program has an interface based on speed. eg if i have a 10 second clip, i set the speed to 200% i end up with a 5 second clip
The second has an interface based on time stretching. eg i set my 10 second clip to time stretch by 50% to end up with a 5 second clip

i also know that speed of 125% equates to a time stretch of 80% cos i had to work that out for something else, but i'm dealing with really specific figures (eg speed of 102.31%) and i can't quite get my head around it

What i need is an equation to work out the factor by which to TIME STRETCH my clips in the second program based on their SPEED in the first.

Can anyone help me?

 

[WopWopWop]

Hey guys, i have a maths problem that i'm hoping somebody can help me with. It may seem easy to you guys, but it's 01:51 AM and..... dammit, i went to art school!

Anyways, the backstory here is that i'm a filmmaker and i'm using two different pieces of software to work on a project. I have a pretty solid workflow to get my files from one to the other, but it misses out adjustments that i make to the speed of my video clips in the first program so that when it gets to the second one the clips are no longer in synch.

Now for the part that has got me stuck.

The first program has an interface based on speed. eg if i have a 10 second clip, i set the speed to 200% i end up with a 5 second clip
The second has an interface based on time stretching. eg i set my 10 second clip to time stretch by 50% to end up with a 5 second clip

i also know that speed of 125% equates to a time stretch of 80% cos i had to work that out for something else, but i'm dealing with really specific figures (eg speed of 102.31%) and i can't quite get my head around it

What i need is an equation to work out the factor by which to TIME STRETCH my clips in the second program based on their SPEED in the first.

Can anyone help me?

Time stretch and speed are simply the inverses of each other:

Let...
t=Time stretch
v=Speed

v=1/t
or
t*v=1

Both time stretch and speed are in decimals.

i.e.
t=Time stretch=80%=0.8
v=Speed=125%=1.25

v*t=1
0.8*1.25=1

This holds true. Try it in a calcuator.

 

[Tharwen]

In your example of 200% and 50%, you can use 2/100 and 100/2 respectively.

So basically, where x = speed increase factor, speed method = (x/100)/100, stretch method = 100/(x/100)

And in your other example, 1.0231/100 and 100/1.0231 will work.

Hopefully that's clear enough.

 

[Redingold]

Take the reciprocal of your speed; that is, speed[sup]-1[/sup]. When you multiply it by your speed, it equals one. That is what you wanted, right?

 

['Aredor]

What those guys said. Or, to put it even simpler, to get your TIME STRETCH in %, simply divide 10,000 by the SPEED in %:

10,000/125% = 80%
10,000/102.31% = 97.742156%