Merge pull request #179 from nukeykt/ym3438

Nuked OPN2: minor optimization + ASIC YM3438 & YM2612 DAC emulation (experimental)

core/sound/sound.c

@@ -89,8 +89,8 @@ void YM3438_Update(int *buffer, int length)
         ym3438_sample[1] += ym3438_accm[j][1];
       }
     }
-    *buffer++ = ym3438_sample[0] * 8;
+    *buffer++ = ym3438_sample[0] * 11;
-    *buffer++ = ym3438_sample[1] * 8;
+    *buffer++ = ym3438_sample[1] * 11;
   }
 }
 

core/sound/ym3438.c

@@ -39,7 +39,7 @@
  *      OPLx decapsulated(Matthew Gambrell, Olli Niemitalo):
  *          OPL2 ROMs.
  *
- * version: 1.0.4
+ * version: 1.0.6
  */
 
 #include <string.h>
@@ -232,6 +232,8 @@ static const Bit32u fm_algorithm[4][6][8] = {
     }
 };
 
+static Bit32u chip_type = ym3438_type_discrete;
+
 void OPN2_DoIO(ym3438_t *chip)
 {
     /* Write signal check */
@@ -506,7 +508,7 @@ void OPN2_PhaseCalcIncrement(ym3438_t *chip)
     basefreq = (fnum << chip->pg_block) >> 2;
 
     /* Apply detune */
-    if (dt & 0x03)
+    if (dt_l)
     {
         if (kcode > 0x1c)
         {
@@ -514,7 +516,7 @@ void OPN2_PhaseCalcIncrement(ym3438_t *chip)
         }
         block = kcode >> 2;
         note = kcode & 0x03;
-        sum = block + 1 + ((dt_l == 3) | (dt_l & 0x02) | ((dt_l != 0) << 3));
+        sum = block + 9 + ((dt_l == 3) | (dt_l & 0x02));
         sum_h = sum >> 1;
         sum_l = sum & 0x01;
         detune = pg_detune[(sum_l << 2) | note] >> (9 - sum_h);
@@ -671,7 +673,7 @@ void OPN2_EnvelopeADSR(ym3438_t *chip)
             }
             break;
         case eg_num_decay:
-            if (!eg_off && (level >> 5) == chip->eg_sl[1])
+            if ((level >> 5) == chip->eg_sl[1])
             {
                 nextstate = eg_num_sustain;
             }
@@ -803,11 +805,11 @@ void OPN2_EnvelopePrepare(ym3438_t *chip)
     chip->eg_ksv = chip->pg_kcode >> (chip->ks[slot] ^ 0x03);
     if (chip->am[slot])
     {
-        chip->eg_am_shift = chip->ams[chip->channel];
+        chip->eg_lfo_am = chip->lfo_am >> eg_am_shift[chip->ams[chip->channel]];
     }
     else
     {
-        chip->eg_am_shift = 0;
+        chip->eg_lfo_am = 0;
     }
     /* Delay TL & SL value */
     chip->eg_tl[1] = chip->eg_tl[0];
@@ -835,7 +837,7 @@ void OPN2_EnvelopeGenerate(ym3438_t *chip)
     level &= 0x3ff;
 
     /* Apply AM LFO */
-    level += chip->lfo_am >> eg_am_shift[chip->eg_am_shift];
+    level += chip->eg_lfo_am;
 
     /* Apply TL */
     if (!(chip->mode_csm && chip->channel == 2 + 1))
@@ -966,6 +968,8 @@ void OPN2_ChOutput(ym3438_t *chip)
     Bit32u channel = chip->channel;
     Bit32u test_dac = chip->mode_test_2c[5];
     Bit16s out;
+    Bit16s sign;
+    Bit32u out_en;
     chip->ch_read = chip->ch_lock;
     if (chip->slot < 12)
     {
@@ -995,14 +999,54 @@ void OPN2_ChOutput(ym3438_t *chip)
     }
     chip->mol = 0;
     chip->mor = 0;
-    if (chip->ch_lock_l)
+
+    if (chip_type == ym3438_type_ym2612)
+    {
+        out_en = ((chip->cycles & 3) == 3) || test_dac;
+        /* YM2612 DAC emulation(not verified) */
+        sign = out >> 8;
+        if (out >= 0)
+        {
+            out++;
+            sign++;
+        }
+        if (chip->ch_lock_l && out_en)
         {
             chip->mol = out;
         }
-    if (chip->ch_lock_r)
+        else
+        {
+            chip->mol = sign;
+        }
+        if (chip->ch_lock_r && out_en)
         {
             chip->mor = out;
         }
+        else
+        {
+            chip->mor = sign;
+        }
+        /* Amplify signal */
+        chip->mol *= 3;
+        chip->mor *= 3;
+    }
+    else
+    {
+        out_en = ((chip->cycles & 3) != 0) || test_dac;
+        /* Discrete YM3438 seems has the ladder effect too */
+        if (out >= 0 && chip_type == ym3438_type_discrete)
+        {
+            out++;
+        }
+        if (chip->ch_lock_l && out_en)
+        {
+            chip->mol = out;
+        }
+        if (chip->ch_lock_r && out_en)
+        {
+            chip->mor = out;
+        }
+    }
 }
 
 void OPN2_FMGenerate(ym3438_t *chip)
@@ -1179,6 +1223,11 @@ void OPN2_Reset(ym3438_t *chip)
     }
 }
 
+void OPN2_SetChipType(Bit32u type)
+{
+    chip_type = type;
+}
+
 void OPN2_Clock(ym3438_t *chip, Bit32u *buffer)
 {
     chip->lfo_inc = chip->mode_test_21[1];
@@ -1350,7 +1399,7 @@ Bit32u OPN2_ReadIRQPin(ym3438_t *chip)
 
 Bit8u OPN2_Read(ym3438_t *chip, Bit32u port)
 {
-    if ((port & 3) == 0)
+    if ((port & 3) == 0 || chip_type == ym3438_type_asic)
     {
         if (chip->mode_test_21[6])
         {

core/sound/ym3438.h

@@ -39,12 +39,18 @@
  *      OPLx decapsulated(Matthew Gambrell, Olli Niemitalo):
  *          OPL2 ROMs.
  *
- * version: 1.0.4
+ * version: 1.0.6
  */
 
 #ifndef YM3438_H
 #define YM3438_H
 
+enum {
+    ym3438_type_discrete = 0,   /* Discrete YM3438 (Teradrive)          */
+    ym3438_type_asic = 1,       /* ASIC YM3438 (MD1 VA7, MD2, MD3, etc) */
+    ym3438_type_ym2612 = 2      /* YM2612 (MD1, MD2 VA2)                */
+};
+
 #include <stdint.h>
 
 typedef uintptr_t       Bitu;
@@ -111,7 +117,7 @@ typedef struct
     Bit8u eg_inc;
     Bit8u eg_ratemax;
     Bit8u eg_sl[2];
-   Bit8u eg_am_shift;
+    Bit8u eg_lfo_am;
     Bit8u eg_tl[2];
     Bit8u eg_state[24];
     Bit16u eg_level[24];
@@ -202,6 +208,7 @@ typedef struct
 } ym3438_t;
 
 void OPN2_Reset(ym3438_t *chip);
+void OPN2_SetChipType(Bit32u type);
 void OPN2_Clock(ym3438_t *chip, Bit32u *buffer);
 void OPN2_Write(ym3438_t *chip, Bit32u port, Bit8u data);
 void OPN2_SetTestPin(ym3438_t *chip, Bit32u value);

libretro/libretro.c

@@ -1106,12 +1106,25 @@ static void check_variables(void)
   environ_cb(RETRO_ENVIRONMENT_GET_VARIABLE, &var);
   {
     orig_value = config.ym3438;
-    if (!strcmp(var.value, "nuked opn2"))
+    if (!strcmp(var.value, "nuked (ym2612)"))
+    {
+      OPN2_SetChipType(ym3438_type_ym2612);
       config.ym3438 = 1;
+    }
+    else if (!strcmp(var.value, "nuked (asic ym3438)"))
+    {
+      OPN2_SetChipType(ym3438_type_asic);
+      config.ym3438 = 2;
+    }
+    else if (!strcmp(var.value, "nuked (discrete ym3438)"))
+    {
+      OPN2_SetChipType(ym3438_type_discrete);
+      config.ym3438 = 3;
+    }
     else
       config.ym3438 = 0;
 
-    if (orig_value != config.ym3438)
+    if (orig_value == 0 && config.ym3438 > 0 || orig_value > 0 && config.ym3438 == 0)
     {
       sound_init();
       sound_reset();
@@ -1656,7 +1669,7 @@ void retro_set_environment(retro_environment_t cb)
       { "genesis_plus_gx_ym2413", "Master System FM; auto|disabled|enabled" },
       { "genesis_plus_gx_dac_bits", "YM2612 DAC quantization; disabled|enabled" },
       #ifdef HAVE_YM3438_CORE
-      { "genesis_plus_gx_ym3438", "YM2612/YM3438 core; mame|nuked opn2" },
+      { "genesis_plus_gx_ym3438", "YM2612/YM3438 core; mame|nuked (ym2612)|nuked (asic ym3438)|nuked (discrete ym3438)" },
       #endif
 
       { "genesis_plus_gx_audio_filter", "Audio filter; disabled|low-pass" },