Why should the host turn controllers into ramps? What if your plugin
wanted to do it's own parameter smoothing?.
How should you handle smoothing for the two main types of real-time
updates? (MIDI and GUI). What is the best smoothing method?
Idealy, we would apply more smoothing to 'slow' parameter updates,
and less smoothing to rapid updates.
The two main sources of updates are from MIDI CCs and the plugin GUI.
My Roland keyboard sends MIDI controlers at about 20 per second (
1 every 50ms ). When I move a knob on my on-screen GUI, I get updates
every 20ms.
Smoothing is filtering. The best filter for controllers is a Low-Pass
filter. You vary the ammount of smoothing by changing the filter's
cuttoff frequency. A low cuttoff gives more smoothing, a high cuttoff less.
My friend Mr Nyquist told me the optimim filter cuttoff for perfect
smoothing is half the update rate. If the updates are at 100Hz, the
filter should be at 50Hz, etc.
MIDI for example...
Update period = 50ms Freq = 1/Period ... 1 / 0.05 = 20Hz Filter cuttoff = period/2 (10 Hz)
GUI...
Update period = 20ms Freq = 1/Period ... 1 / 0.02 = 50Hz Filter cuttoff = 25 Hz
Example events for optimum smoothing...
Host receives MIDI CC values { 1,2,3.. }, host sends events...Event 1: Time:0 End Value: 1 Duration: 50ms
Event 2: Time:50 End Value: 2 Duration: 50ms
Event 3: Time:100 End Value: 3 Duration: 50ms
etc....
Hmmmm..those look familiar.
Best Regards, Jeff
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