Fix PC-FX ADPCM frequency behavior (#6213)

* Fix PC-FX ADPCM frequency behavior
but it's still noisy and imperfect; Add imperfect_features for this.
huc6230.cpp : Fix ADPCM frequency, Make ADPCM less louder, Fix naming related to patents, Fix stream sample rate related to PSG output rate, Add notes
huc6272.cpp : Fix ADPCM frequency

* huc6230.cpp : Fix spacing

* huc6272.cpp : Add patent for reference

* huc6230.cpp, huc6272.cpp : Add patent for reference

src/devices/sound/huc6230.cpp

@@ -2,15 +2,17 @@
 // copyright-holders:cam900
 /*
     Hudson HuC6230 SoundBox
-    HuC6280 PSG with ADPCM
+    PSG part of HuC6280 with ADPCM
 
     TODO:
     - Volume is linear?
     - Make it actually working
-    - Implement CDDA Volume
+    - Implement/Correct VCA (Voltage Controlled Amplifier) behavior
 
     Related patent:
     - https://patents.google.com/patent/US5692099
+    - https://patents.google.com/patent/US6453286
+	- https://patents.google.com/patent/US5548655A
 */
 
 #include "emu.h"
@@ -33,8 +35,8 @@ void huc6230_device::sound_stream_update(sound_stream &stream, stream_sample_t *
 			if (!channel->m_playing)
 				continue;
 
-			outputs[0][i] = clamp(outputs[0][i] + ((channel->m_output * channel->m_lvol) >> 2), -32768, 32767);
-			outputs[1][i] = clamp(outputs[1][i] + ((channel->m_output * channel->m_rvol) >> 2), -32768, 32767);
+			outputs[0][i] = clamp(outputs[0][i] + ((channel->m_output * channel->m_lvol) >> 3), -32768, 32767);
+			outputs[1][i] = clamp(outputs[1][i] + ((channel->m_output * channel->m_rvol) >> 3), -32768, 32767);
 		}
 	}
 }
@@ -83,19 +85,19 @@ WRITE8_MEMBER( huc6230_device::write )
 	}
 	else if (offset < 0x16)
 	{
-		m_cdda_lvol = data & 0x3f;
-		m_cdda_cb(0, m_cdda_lvol);
+		m_pcm_lvol = data & 0x3f;
+		m_vca_cb(0, m_pcm_lvol);
 	}
 	else if (offset < 0x17)
 	{
-		m_cdda_rvol = data & 0x3f;
-		m_cdda_cb(1, m_cdda_rvol);
+		m_pcm_rvol = data & 0x3f;
+		m_vca_cb(1, m_pcm_rvol);
 	}
 }
 
 TIMER_CALLBACK_MEMBER(huc6230_device::adpcm_timer)
 {
-	int frq = (1 << m_adpcm_freq);
+	const unsigned frq = (1 << m_adpcm_freq);
 	for (int adpcm = 0; adpcm < 2; adpcm++)
 	{
 		adpcm_channel *channel = &m_adpcm_channel[adpcm];
@@ -113,7 +115,7 @@ TIMER_CALLBACK_MEMBER(huc6230_device::adpcm_timer)
 		channel->m_pos++;
 		channel->m_input = m_adpcm_update_cb[adpcm]();
 
-		if (channel->m_pos > frq)
+		if (channel->m_pos >= frq)
 		{
 			channel->m_pos = 0;
 			channel->m_prev_sample = channel->m_curr_sample;
@@ -143,10 +145,10 @@ huc6230_device::huc6230_device(const machine_config &mconfig, const char *tag, d
 	, m_stream(nullptr)
 	, m_psg(*this, "psg")
 	, m_adpcm_freq(0)
-	, m_cdda_lvol(0)
-	, m_cdda_rvol(0)
+	, m_pcm_lvol(0)
+	, m_pcm_rvol(0)
 	, m_adpcm_update_cb{{*this}, {*this}}
-	, m_cdda_cb(*this)
+	, m_vca_cb(*this)
 {
 }
 
@@ -169,9 +171,9 @@ void huc6230_device::device_start()
 	for (auto &cb : m_adpcm_update_cb)
 		cb.resolve_safe(0);
 
-	m_cdda_cb.resolve_safe();
+	m_vca_cb.resolve_safe();
 
-	m_stream = machine().sound().stream_alloc(*this, 2, 2, clock() / 96);
+	m_stream = machine().sound().stream_alloc(*this, 2, 2, clock() / 6);
 	m_adpcm_timer = machine().scheduler().timer_alloc(timer_expired_delegate(FUNC(huc6230_device::adpcm_timer),this));
 
 	for (int i = 0; i < 2; i++)
@@ -196,13 +198,13 @@ void huc6230_device::device_start()
 		save_item(NAME(m_adpcm_channel[i].m_input), i);
 	}
 	save_item(NAME(m_adpcm_freq));
-	save_item(NAME(m_cdda_lvol));
-	save_item(NAME(m_cdda_rvol));
+	save_item(NAME(m_pcm_lvol));
+	save_item(NAME(m_pcm_rvol));
 }
 
 void huc6230_device::device_clock_changed()
 {
-	m_stream->set_sample_rate(clock() / 96);
+	m_stream->set_sample_rate(clock() / 6);
 	attotime adpcm_period = clocks_to_attotime(682);
 	m_adpcm_timer->adjust(adpcm_period, 0, adpcm_period);
 }

src/devices/sound/huc6230.h

@@ -11,10 +11,12 @@
 class huc6230_device : public device_t, public device_sound_interface
 {
 public:
+	static constexpr feature_type imperfect_features() { return feature::SOUND; } // Incorrect ADPCM
+
 	huc6230_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
 	template <unsigned N> auto adpcm_update_cb() { return m_adpcm_update_cb[N].bind(); }
-	auto cdda_cb() { return m_cdda_cb.bind(); }
+	auto vca_callback() { return m_vca_cb.bind(); }
 
 	// write only
 	DECLARE_WRITE8_MEMBER( write );
@@ -48,13 +50,13 @@ private:
 	required_device<c6280_device> m_psg;
 	adpcm_channel m_adpcm_channel[2];
 	uint32_t m_adpcm_freq;
-	uint32_t m_cdda_lvol;
-	uint32_t m_cdda_rvol;
+	uint32_t m_pcm_lvol;
+	uint32_t m_pcm_rvol;
 
 	TIMER_CALLBACK_MEMBER(adpcm_timer);
 
 	devcb_read8 m_adpcm_update_cb[2];
-	devcb_write8 m_cdda_cb;
+	devcb_write8 m_vca_cb;
 };
 
 DECLARE_DEVICE_TYPE(HuC6230, huc6230_device)

src/devices/video/huc6272.cpp

@@ -10,6 +10,8 @@
 
     ADPCM related patents:
     - https://patents.google.com/patent/US5692099
+    - https://patents.google.com/patent/US6453286
+	- https://patents.google.com/patent/US5548655A
 
 ***************************************************************************/
 
@@ -497,9 +499,9 @@ uint8_t huc6272_device::adpcm_update(int chan)
 	if (!m_adpcm.playing[chan])
 		return 0;
 
-	int rate = (1 << m_adpcm.rate);
+	const unsigned rate = (1 << m_adpcm.rate);
 	m_adpcm.pos[chan]++;
-	if (m_adpcm.pos[chan] > rate)
+	if (m_adpcm.pos[chan] >= rate)
 	{
 		if (m_adpcm.input[chan] == -1)
 		{
@@ -541,6 +543,7 @@ uint8_t huc6272_device::adpcm_update(int chan)
 			if (m_adpcm.nibble[chan] >= 28)
 				m_adpcm.input[chan] = -1;
 		}
+		m_adpcm.pos[chan] = 0;
 	}
 
 	return (m_adpcm.input[chan] >> m_adpcm.nibble[chan]) & 0xf;

src/devices/video/huc6272.h

@@ -27,6 +27,8 @@ class huc6272_device :  public device_t,
 						public device_memory_interface
 {
 public:
+	static constexpr feature_type imperfect_features() { return feature::SOUND | feature::GRAPHICS; } // Incorrect ADPCM and Graphics
+
 	// construction/destruction
 	huc6272_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 

src/mame/drivers/pcfx.cpp

@@ -455,7 +455,7 @@ void pcfx_state::pcfx(machine_config &config)
 	huc6230_device &huc6230(HuC6230(config, "huc6230", XTAL(21'477'272)));
 	huc6230.adpcm_update_cb<0>().set("huc6272", FUNC(huc6272_device::adpcm_update_0));
 	huc6230.adpcm_update_cb<1>().set("huc6272", FUNC(huc6272_device::adpcm_update_1));
-	huc6230.cdda_cb().set("huc6272", FUNC(huc6272_device::cdda_update));
+	huc6230.vca_callback().set("huc6272", FUNC(huc6272_device::cdda_update));
 	huc6230.add_route(0, "lspeaker", 1.0);
 	huc6230.add_route(1, "rspeaker", 1.0);
 }