[sdiy] MIDI volume to volts formula

rsdio at audiobanshee.com rsdio at audiobanshee.com
Fri Jun 8 04:44:54 CEST 2018

Part of my point is that there is surely a lookup table or mapping involved, so even though the hardware is measuring “c - t” directly, these values can easily be converted to “1 / t” with an appropriate map.

On Jun 7, 2018, at 7:28 PM, rsdio at audiobanshee.com wrote:
> Well, it’s not literally “TIME” but something like “1 - t” or, more accurately, “c - t” where c is a constant like 127. “t” is time in both functions. Rather than reciprocal time, it’s negative time (because of the counter decrementing).
> As I mentioned earlier, Velocity is distance over time, or “d / t” but distance is fixed for a piano action so that becomes “1 / t” effectively. For minimal processing, MIDI keyboards transmit “c - t” instead of “1 / t"
> Another consideration is that if a counter is running fast enough to detect small differences for fast velocities, then the count might actually have to start with a much larger value than 127. They might even start with 1023 and count down, but mapping 0 to 127 and 1023 to 1 (in other words, compressing the 1024 range to a smaller 128 range). I haven’t looked at the actual keyboard scanning rates or velocity histograms to see what the numbers show.

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