update ymfm

src/engine/platform/sound/ymfm/ymfm_fm.h

@@ -426,7 +426,7 @@ protected:
 	void assign_operators();
 
 	// update the state of the given timer
-	void update_timer(uint32_t which, uint32_t enable);
+	void update_timer(uint32_t which, uint32_t enable, int32_t delta_clocks);
 
 	// internal state
 	ymfm_interface &m_intf;          // reference to the system interface
@@ -436,6 +436,7 @@ protected:
 	uint8_t m_irq_mask;              // mask of which bits signal IRQs
 	uint8_t m_irq_state;             // current IRQ state
 	uint8_t m_timer_running[2];      // current timer running state
+	uint8_t m_total_clocks;          // low 8 bits of the total number of clocks processed
 	uint32_t m_active_channels;      // mask of active channels (computed by prepare)
 	uint32_t m_modified_channels;    // mask of channels that have been modified
 	uint32_t m_prepare_count;        // counter to do periodic prepare sweeps

src/engine/platform/sound/ymfm/ymfm_fm.ipp

@@ -1236,6 +1236,7 @@ void fm_engine_base<RegisterType>::save_restore(ymfm_saved_state &state)
 	state.save_restore(m_irq_state);
 	state.save_restore(m_timer_running[0]);
 	state.save_restore(m_timer_running[1]);
+	state.save_restore(m_total_clocks);
 
 	// save the register/family data
 	m_regs.save_restore(state);
@@ -1261,6 +1262,9 @@ void fm_engine_base<RegisterType>::save_restore(ymfm_saved_state &state)
 template<class RegisterType>
 uint32_t fm_engine_base<RegisterType>::clock(uint32_t chanmask)
 {
+	// update the clock counter
+	m_total_clocks++;
+
 	// if something was modified, prepare
 	// also prepare every 4k samples to catch ending notes
 	if (m_modified_channels != 0 || m_prepare_count++ >= 4096)
@@ -1455,7 +1459,7 @@ void fm_engine_base<RegisterType>::assign_operators()
 //-------------------------------------------------
 
 template<class RegisterType>
-void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable)
+void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable, int32_t delta_clocks)
 {
 	// if the timer is live, but not currently enabled, set the timer
 	if (enable && !m_timer_running[tnum])
@@ -1463,6 +1467,9 @@ void fm_engine_base<RegisterType>::update_timer(uint32_t tnum, uint32_t enable)
 		// period comes from the registers, and is different for each
 		uint32_t period = (tnum == 0) ? (1024 - m_regs.timer_a_value()) : 16 * (256 - m_regs.timer_b_value());
 
+		// caller can also specify a delta to account for other effects
+		period += delta_clocks;
+
 		// reset it
 		m_intf.ymfm_set_timer(tnum, period * OPERATORS * m_clock_prescale);
 		m_timer_running[tnum] = 1;
@@ -1499,7 +1506,7 @@ void fm_engine_base<RegisterType>::engine_timer_expired(uint32_t tnum)
 
 	// reset
 	m_timer_running[tnum] = false;
-	update_timer(tnum, 1);
+	update_timer(tnum, 1, 0);
 }
 
 
@@ -1557,9 +1564,11 @@ void fm_engine_base<RegisterType>::engine_mode_write(uint8_t data)
 			reset_mask |= RegisterType::STATUS_TIMERA;
 		set_reset_status(0, reset_mask);
 
-		// load timers
+		// load timers; note that timer B gets a small negative adjustment because
-		update_timer(1, m_regs.load_timer_b());
+		// the *16 multiplier is free-running, so the first tick of the clock
-		update_timer(0, m_regs.load_timer_a());
+		// is a bit shorter
+		update_timer(1, m_regs.load_timer_b(), -(m_total_clocks & 15));
+		update_timer(0, m_regs.load_timer_a(), 0);
 	}
 }
 

src/engine/platform/sound/ymfm/ymfm_opm.cpp

@@ -74,6 +74,7 @@ opm_registers::opm_registers() :
 		m_lfo_waveform[2][index] = am | (pm << 8);
 
 		// waveform 3 is noise; it is filled in dynamically
+		m_lfo_waveform[3][index] = 0;
 	}
 }
 

src/engine/platform/sound/ymfm/ymfm_opn.cpp

@@ -2398,8 +2398,8 @@ void ym2612::generate(output_data *output, uint32_t numsamples)
 		// a better sound mixer than we usually have, so just average over the six
 		// channels; also apply a 64/65 factor to account for the discontinuity
 		// adjustment above
-		output->data[0] = (output->data[0] << 7) * 64 / (6 * 65);
+		output->data[0] = (output->data[0] * 128) * 64 / (6 * 65);
-		output->data[1] = (output->data[1] << 7) * 64 / (6 * 65);
+		output->data[1] = (output->data[1] * 128) * 64 / (6 * 65);
 	}
 }
 
@@ -2432,8 +2432,8 @@ void ym3438::generate(output_data *output, uint32_t numsamples)
 
 		// YM3438 doesn't have the same DAC discontinuity, though its output is
 		// multiplexed like the YM2612
-		output->data[0] = (output->data[0] << 7) / 6;
+		output->data[0] = (output->data[0] * 128) / 6;
-		output->data[1] = (output->data[1] << 7) / 6;
+		output->data[1] = (output->data[1] * 128) / 6;
 	}
 }
 

src/engine/platform/sound/ymfm/ymfm_opn.h

@@ -763,7 +763,7 @@ public:
 
 protected:
 	// simulate the DAC discontinuity
-	int32_t dac_discontinuity(int32_t value) const { return (value < 0) ? (value - 2) : (value + 3); }
+	constexpr int32_t dac_discontinuity(int32_t value) const { return (value < 0) ? (value - 2) : (value + 3); }
 
 	// internal state
 	uint16_t m_address;              // address register