# [PD] Equation question

day 5 day5ive at gmail.com
Mon Nov 21 01:33:00 CET 2005

```Thanks to both of you gentlemen for very helpful responses.

./d5

On Nov 20, 2005, at 6:11 PM, Frank Barknecht wrote:

> Hallo,
> day 5 hat gesagt: // day 5 wrote:
>
>> what formula might one be using to determine periodicity as rate in
>> ms ?
>>
>> For example, say you know total frames of a video file and you know
>> this file is 24 fps. You can say that it vibrates at 24 Hz so what is
>> the periodicity of the wave in ms ?
>
> You just take the inverse to convert between period (or wavelength)
> and frequency (like fps or Hz), so it's
>
> [expr 1/\$f1].
>
> If you want to drive a [metro] with that, you have to take into
> account, that the metro wants milliseconds. So you'd use:
>
> [expr 1000 * 1/\$f1] == [expr 1000/\$f1]
>
> to convert from fps to a metro period, where the period is the time it
> takes for one frame to pass.
>
> It's similar with converting BPM to a [metro] period, however there
> you have the additional problem, that BPM is beats per minute. As a
> minute has 60 seconds and a second has 1000 milliseconds, you do this:
>
> [expr 60*1000 * 1/\$f1] or better: [expr 60000/\$f1]
>
> It works both ways: Sending 120 (BPM) into this will give you 500
> (ms), and sending 500 (ms) into it wil give you 120 (BPM).

On Nov 20, 2005, at 5:58 PM, Claude Heiland-Allen wrote:

> Hi,
>
> I didn't try the patch, as I don't have Gem installed, and as a result
> I may be missing the point in what follows.  But some useful equations
> (which you can rearrange using very basic algebra):
>
> (time per frame in ms) = 1000 / (rate in fps)
>
> (total time in ms) = (number of frames) * 1000 / (rate in fps)
>
> (time per beat in ms) = 60000 / (rate in bpm)
>
>
> A way of checking equations for plausibility is described in the first
> few paragraphs here:
> http://en.wikipedia.org/wiki/Dimensional_analysis

```