[LAD] Re: Calculating logarithmic curve for controller automation

On Thu, Feb 23, 2023 at 08:43:52PM +0100, Jeanette C. wrote:

> In my example: I want to change the tempo from 120BPM to 150BPM over
> four bars of equal length.

What you want here is probably an exponential mapping from bars or
beats to tempo. 

For example if you want to change from 1 to 4, a linear mapping 
would have (1 + 4) / 2 = 2.5 halfway, and an exponential mapping
would have sqrt (1 * 4) = 2 halfway.

For 120 to 150 it would make very little difference, 135 vs 134.16.

So if the start and end values are A and B, you would make a linear
function from log (A) to log (B), and then use exp () on that to
find the tempo at any point.

Note that this is a exponential mapping from bars or beats to 
tempo, not from time to tempo (because as the tempo is changing,
so does the duration of a bars or beat).

Ciao,

-- 
FA

_______________________________________________
Linux-audio-dev mailing list -- linux-audio-dev-cunTk1MwBs/[email protected]
To unsubscribe send an email to linux-audio-dev-leave-cunTk1MwBs/[email protected]