mirror of
https://github.com/TomHarte/CLK.git
synced 2024-12-25 18:30:21 +00:00
56 lines
1.4 KiB
C++
56 lines
1.4 KiB
C++
//
|
|
// KeyLevelScaler.hpp
|
|
// Clock Signal
|
|
//
|
|
// Created by Thomas Harte on 02/05/2020.
|
|
// Copyright © 2020 Thomas Harte. All rights reserved.
|
|
//
|
|
|
|
#ifndef KeyLevelScaler_h
|
|
#define KeyLevelScaler_h
|
|
|
|
namespace Yamaha::OPL {
|
|
|
|
template <int frequency_precision> class KeyLevelScaler {
|
|
public:
|
|
|
|
/*!
|
|
Sets the current period associated with the channel that owns this envelope generator;
|
|
this is used to select a key scaling rate if key-rate scaling is enabled.
|
|
*/
|
|
void set_period(int period, int octave) {
|
|
constexpr int key_level_scales[16] = {0, 48, 64, 74, 80, 86, 90, 94, 96, 100, 102, 104, 106, 108, 110, 112};
|
|
constexpr int masks[2] = {~0, 0};
|
|
|
|
// A two's complement assumption is embedded below; the use of masks relies
|
|
// on the sign bit to clamp to zero.
|
|
level_ = key_level_scales[period >> (frequency_precision - 4)];
|
|
level_ -= 16 * (octave ^ 7);
|
|
level_ &= masks[(level_ >> ((sizeof(int) * 8) - 1)) & 1];
|
|
}
|
|
|
|
/*!
|
|
Enables or disables key-rate scaling.
|
|
*/
|
|
void set_key_scaling_level(int level) {
|
|
// '7' is just a number large enough to render all possible scaling coefficients as 0.
|
|
constexpr int key_level_scale_shifts[4] = {7, 1, 2, 0};
|
|
shift_ = key_level_scale_shifts[level];
|
|
}
|
|
|
|
/*!
|
|
@returns The current attenuation level due to key-level scaling.
|
|
*/
|
|
int attenuation() const {
|
|
return level_ >> shift_;
|
|
}
|
|
|
|
private:
|
|
int level_ = 0;
|
|
int shift_ = 0;
|
|
};
|
|
|
|
}
|
|
|
|
#endif /* KeyLevelScaler_h */
|