* Combine key frequency with step

- Reduces the number of multiplies inside oscillators

Author: [email protected]

DisplayLowFrequencyOscillator.cpp

@@ -25,7 +25,7 @@ void UpdateLowFrequencyOscillatorDisplay(HANDLE hOut)
 		buf[x] = positive;
 
 	// plot low-frequency oscillator value
-	float const lfo = lfo_state.Update(lfo_config, 1.0f, 0.0f);
+	float const lfo = lfo_state.Update(lfo_config, 0.0f);
 	int grid_x = Clamp(FloorInt(18.0f * lfo + 18.0f), 0, 35);
 	buf[grid_x / 2].Char.UnicodeChar = plot[grid_x & 1];
 

DisplayOscillatorWaveform.cpp

@@ -43,7 +43,7 @@ static float UpdateWaveformStep(NoteOscillatorConfig config[], OscillatorState s
 		if (config[o].sync_enable)
 			config[o].sync_phase = config[o].frequency / config[0].frequency;
 		if (config[o].sub_osc_mode)
-			value += config[o].sub_osc_amplitude * SubOscillator(config[o], state[o], 1, delta[o]);
+			value += config[o].sub_osc_amplitude * SubOscillator(config[o], state[o], delta[o]);
 		value += state[o].Compute(config[o], delta[o]);
 		state[o].Advance(config[o], step[o]);
 	}
@@ -68,7 +68,7 @@ void UpdateOscillatorWaveformDisplay(HANDLE hOut, BASS_INFO const &info, int con
 
 	// get low-frequency oscillator value
 	// (assume it is constant for the duration)
-	float const lfo = lfo_state.Update(lfo_config, 1.0f, 0.0f);
+	float const lfo = lfo_state.Update(lfo_config, 0.0f);
 
 	// how many cycles to plot?
 	int cycle = osc_config[0].cycle;

Oscillator.cpp

@@ -24,12 +24,12 @@ void OscillatorState::Start()
 }
 
 // update oscillator
-float OscillatorState::Update(OscillatorConfig const &config, float const frequency, float const step)
+float OscillatorState::Update(OscillatorConfig const &config, float const step)
 {
 	if (!config.enable)
 		return 0.0f;
 
-	float const delta = config.frequency * config.adjust * frequency * step;
+	float const delta = config.frequency * config.adjust * step;
 
 	// compute oscillator value
 	float const value = Compute(config, delta);

Oscillator.h

@@ -68,7 +68,7 @@ class OscillatorState
 	void Start();
 
 	// update the oscillator by one step
-	float Update(OscillatorConfig const &config, float frequency, float const step);
+	float Update(OscillatorConfig const &config, float const step);
 
 	// compute the oscillator value
 	float Compute(OscillatorConfig const &config, float delta);

SubOscillator.cpp

@@ -20,10 +20,10 @@ const char * const sub_osc_name[SUBOSC_COUNT] =
 };
 
 // sub-oscillator
-float SubOscillator(NoteOscillatorConfig const &config, OscillatorState const &state, float frequency, float step)
+float SubOscillator(NoteOscillatorConfig const &config, OscillatorState const &state, float step)
 {
 	float sub_value = (state.index & config.sub_osc_mode) ? -1.0f : 1.0f;
-	float const w = frequency * step * POLYBLEP_WIDTH;
+	float const w = step * POLYBLEP_WIDTH;
 	if (state.phase < 0.5f)
 	{
 		float sub_prev = ((state.index - 1) & config.sub_osc_mode) ? -1.0f : 1.0f;

SubOscillator.h

@@ -23,4 +23,4 @@ enum SubOscillatorMode
 extern const char * const sub_osc_name[SUBOSC_COUNT];
 
 // compute sub-oscillator value
-extern float SubOscillator(NoteOscillatorConfig const &config, OscillatorState const &state, float frequency, float step);
+extern float SubOscillator(NoteOscillatorConfig const &config, OscillatorState const &state, float step);

synth.cpp

@@ -71,7 +71,7 @@ DWORD CALLBACK WriteStream(HSTREAM handle, short *buffer, DWORD length, void *us
 		memset(buffer, 0, length);
 
 		// advance low-frequency oscillator
-		float lfo = lfo_state.Update(lfo_config, 1.0f, float(count) / info.freq);
+		float lfo = lfo_state.Update(lfo_config, float(count) / info.freq);
 
 		// compute shared oscillator values
 		for (int o = 0; o < NUM_OSCILLATORS; ++o)
@@ -102,7 +102,7 @@ DWORD CALLBACK WriteStream(HSTREAM handle, short *buffer, DWORD length, void *us
 		if ((c & (BLOCK_UPDATE_SAMPLES - 1)) == 0)
 		{
 			// get low-frequency oscillator value
-			lfo = lfo_state.Update(lfo_config, 1.0f, block_step);
+			lfo = lfo_state.Update(lfo_config, block_step);
 
 			// compute shared oscillator values
 			for (int o = 0; o < NUM_OSCILLATORS; ++o)
@@ -146,18 +146,20 @@ DWORD CALLBACK WriteStream(HSTREAM handle, short *buffer, DWORD length, void *us
 			// key velocity
 			float const key_vel = voice_vel[v] / 64.0f;
 
-			// update oscillator
+			// key frequency times step
+			float const key_step = key_freq * step;
+
+			// update oscillators
 			// (assume key follow)
 			float osc_value = 0.0f;
 			for (int o = 0; o < NUM_OSCILLATORS; ++o)
 			{
 				if (osc_config[o].sub_osc_mode && osc_config[o].sub_osc_amplitude)
-					osc_value += osc_config[o].sub_osc_amplitude * SubOscillator(osc_config[o], osc_state[v][o], key_freq, step);
-				osc_value += osc_state[v][o].Update(osc_config[o], key_freq, step);
+					osc_value += osc_config[o].sub_osc_amplitude * SubOscillator(osc_config[o], osc_state[v][o], key_step);
+				osc_value += osc_state[v][o].Update(osc_config[o], key_step);
 			}
 
 			// update filter
-			float flt_value;
 			if (flt_config.enable)
 			{
 				if ((c & (BLOCK_UPDATE_SAMPLES - 1)) == 0)
@@ -174,16 +176,11 @@ DWORD CALLBACK WriteStream(HSTREAM handle, short *buffer, DWORD length, void *us
 				}
 
 				// get filtered oscillator value
-				flt_value = flt_state[v].Update(flt_config, osc_value);
-			}
-			else
-			{
-				// pass unfiltered value
-				flt_value = osc_value;
+				osc_value = flt_state[v].Update(flt_config, osc_value);
 			}
 
 			// apply amplifier level and accumulate result
-			sample += flt_value * amp_config.GetLevel(amp_env_amplitude, key_vel);
+			sample += osc_value * amp_config.GetLevel(amp_env_amplitude, key_vel);
 		}
 
 		// left and right channels are the same