67 lines
2.0 KiB
Python
67 lines
2.0 KiB
Python
#!/usr/bin/env python3
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start_pitch = 36 # C2
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end_pitch = 84 # C6
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pitch_A0 = 21
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pitch_C1 = 24
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pitch_A4 = 69
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freq_A4 = 440
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pitch_D5 = 74
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pitch_F5 = 77
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def pitch_to_freq(pitch):
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dist_A4 = pitch - pitch_A4
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factor = pow(2, abs(dist_A4) / 12)
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if dist_A4 > 0:
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# Notes after A4 are about 20 cents flat
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factor = factor * pow(2, 20 / 12 / 100)
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if pitch >= pitch_D5:
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# After D5 it's about another 10 cents flat
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factor = factor * pow(2, 10 / 12 / 100)
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if pitch >= pitch_F5:
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# After F5 it's about another 10 cents flat
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factor = factor * pow(2, 10 / 12 / 100)
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return freq_A4 * factor
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else:
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return freq_A4 / factor
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def pitch_to_period_micros(pitch):
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return 1 / pitch_to_freq(pitch) * 1000 * 1000
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pitch_names = ["A", "A#", "B", "C", "C#", "D", "D#", "E", "F", "F#", "G", "G#"]
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def pitch_to_name(pitch):
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return pitch_names[(pitch - pitch_A0) % 12] + str(int((pitch - pitch_C1) / 12) + 1)
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print("#pragma once")
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print("")
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print("constexpr unsigned int midi_pitch_offset = " + str(start_pitch) + ";")
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print("constexpr unsigned int midi_pitch_max = " + str(end_pitch) + ";")
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print("// period is in units of 0.5 us, instead of 1 us")
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print("constexpr unsigned long midi_pitch_period[" + str(end_pitch - start_pitch) + "] = {")
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for i in range(start_pitch, end_pitch):
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period = int(2.0 * pitch_to_period_micros(i))
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name = pitch_to_name(i)
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if name == "D3" or name == "D#3" or name == "E3":
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period = int(period / 2)
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print(" " + str(period) + "ul,\t// " + name)
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print("};")
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print("")
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print("// scale factors for bend values from 0 to 255")
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print("// We don't support the full 16385 levels of MIDI bend")
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print("// MIDI bend values have to be converted first to the nearest supported one")
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print("constexpr float midi_pitch_bend_scale[256] = {")
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for i in range(0, 256):
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factor = pow(2, (8192 - i * 64) / 49152)
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print(" " + str(factor) + "f,\t// " + str(i))
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print("};") |