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