Fix slow/missing note OPL2 playback on complex songs

sw/flash_settings.h

@@ -25,7 +25,7 @@ extern "C" {
 #include <stdbool.h>
 
 #define SETTINGS_MAGIC 0x70677573  // "pgus" in ascii
-#define SETTINGS_VERSION 2
+#define SETTINGS_VERSION 3
 
 // Settings struct has generous padding for future settings by aligning to 4 bytes
 typedef struct Settings {

sw/opl/opl_pico.c

@@ -383,7 +383,7 @@ static void OPLTimer_CalculateEndTime(opl_timer_t *timer)
     }
 }
 
-static void WriteRegister(unsigned int reg_num, unsigned int value)
+void OPL_Pico_WriteRegister(unsigned int reg_num, unsigned int value)
 {
     switch (reg_num)
     {
@@ -450,7 +450,7 @@ void OPL_Pico_PortWrite(opl_port_t port, unsigned int value)
     }
     else if (port == OPL_DATA_PORT)
     {
-        WriteRegister(register_num, value);
+        OPL_Pico_WriteRegister(register_num, value);
     }
 }
 

sw/picogus.cpp

@@ -69,10 +69,9 @@ extern void sbdsp_process();
 #include "opl.h"
 void play_adlib(void);
 extern "C" int OPL_Pico_Init(unsigned int);
-extern "C" void OPL_Pico_PortWrite(opl_port_t, unsigned int);
 extern "C" unsigned int OPL_Pico_PortRead(opl_port_t);
-// #include "cmd_buffers.h"
-// cms_buffer_t opl_buffer = { {0}, 0, 0 };
+#include "cmd_buffers.h"
+cms_buffer_t opl_buffer = { {0}, 0, 0 };
 #endif
 
 #ifdef CDROM
@@ -648,29 +647,18 @@ __force_inline void handle_iow(void) {
     if ((port >> 4) == sb_port_test) {
         switch (port - settings.SB.basePort) {
         // OPL ports
-        case 0x8 ... 0x9:
+        case 0x8:
             // Fast write
-            // pio_sm_put(pio0, IOW_PIO_SM, IO_END);
-            pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
-            /*
-            opl_buffer.cmds[opl_buffer.head++] = {
-                OPL_REGISTER_PORT,
-                (uint8_t)(iow_read & 0xFF)
-            };
+            pio_sm_put(pio0, IOW_PIO_SM, IO_END);
+            // pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
+            opl_buffer.cmds[opl_buffer.head].addr = (uint16_t)(iow_read & 0xFF);
             // Fast write - return early as we've already written 0x0u to the PIO
             return;
-            */
-            OPL_Pico_PortWrite((opl_port_t)(port & 1), (uint8_t)(iow_read & 0xFF));
             break;
-        /*
         case 0x9:
             pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
-            opl_buffer.cmds[opl_buffer.head++] = {
-                OPL_DATA_PORT,
-                (uint8_t)(iow_read & 0xFF)
-            };
+            opl_buffer.cmds[opl_buffer.head++].data = (uint8_t)(iow_read & 0xFF);
             break;
-        */
         // DSP ports
         default:
             pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);                        
@@ -690,29 +678,19 @@ __force_inline void handle_iow(void) {
 #endif
 #if defined(SOUND_OPL)
     if ((port & 0x3fe) == settings.SB.oplBasePort) {
-        /*
-        // Fast write
-        pio_sm_put(pio0, IOW_PIO_SM, IO_END);
-        opl_buffer.cmds[opl_buffer.head++] = {
-            OPL_REGISTER_PORT,
-            (uint8_t)(iow_read & 0xFF)
-        };
-        // Fast write - return early as we've already written 0x0u to the PIO
-        return;
-        */
-        pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
-        OPL_Pico_PortWrite((opl_port_t)(port & 1), (uint8_t)(iow_read & 0xFF));
-    /*
-    } else if (port == settings.SB.oplBasePort + 1) {
-        pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
-        if (settings.SB.oplSpeedSensitive) {
-            busy_wait_us(1); // busy wait for speed sensitive games
+        if ((port & 1) == 0) {
+            // Fast write
+            pio_sm_put(pio0, IOW_PIO_SM, IO_END);
+            opl_buffer.cmds[opl_buffer.head].addr = (uint16_t)(iow_read & 0xFF);
+            // Fast write - return early as we've already written 0x0u to the PIO
+            return;
+        } else {
+            pio_sm_put(pio0, IOW_PIO_SM, IO_WAIT);
+            if (settings.SB.oplSpeedSensitive) {
+                busy_wait_us(1); // busy wait for speed sensitive games
+            }
+            opl_buffer.cmds[opl_buffer.head++].data = (uint8_t)(iow_read & 0xFF);
         }
-        opl_buffer.cmds[opl_buffer.head++] = {
-            OPL_DATA_PORT,
-            (uint8_t)(iow_read & 0xFF)
-        };
-    */
     } else // if follows down below
 #endif // SOUND_OPL
 #ifdef SOUND_TANDY
@@ -848,12 +826,10 @@ __force_inline void handle_ior(void) {
         pio_sm_put(pio0, IOR_PIO_SM, IO_WAIT);
         switch (port - settings.SB.basePort) {
         case 0x8:
-            /*
             // wait for OPL buffer to process
             while (opl_buffer.tail != opl_buffer.head) {
                 tight_loop_contents();
             }
-            */
             pio_sm_put(pio0, IOR_PIO_SM, IOR_SET_VALUE | OPL_Pico_PortRead(OPL_REGISTER_PORT));
             break;
         default:
@@ -876,12 +852,10 @@ __force_inline void handle_ior(void) {
     if (port == settings.SB.oplBasePort) {
         // Tell PIO to wait for data
         pio_sm_put(pio0, IOR_PIO_SM, IO_WAIT);
-        /*
         // wait for OPL buffer to process
         while (opl_buffer.tail != opl_buffer.head) {
             tight_loop_contents();
         }
-        */
         pio_sm_put(pio0, IOR_PIO_SM, IOR_SET_VALUE | OPL_Pico_PortRead(OPL_REGISTER_PORT));
     } else // if follows down below
 #endif

sw/sbplay.cpp

@@ -31,7 +31,7 @@
 
 #include "opl.h"
 extern "C" void OPL_Pico_simple(int16_t *buffer, uint32_t nsamples);
-extern "C" void OPL_Pico_PortWrite(opl_port_t, unsigned int);
+extern "C" void OPL_Pico_WriteRegister(unsigned int reg_num, unsigned int value);
 
 #include "audio_fifo.h"
 #if SOUND_SB
@@ -192,7 +192,9 @@ void play_adlib() {
     uint32_t cd_left = 0;
     uint32_t cd_index = 0;
 
-    int16_t opl_samples[SAMPLES_PER_BUFFER * 2] = {0};
+    constexpr uint32_t OPL_SAMPLE_COUNT = 8;
+    constexpr uint32_t OPL_BUFFER_BITS = (OPL_SAMPLE_COUNT << 1) - 1;
+    int16_t opl_samples[OPL_SAMPLE_COUNT << 1] = {0};
     uint32_t opl_ratio = fixed_ratio(49716, 44100);
     printf("opl_ratio: %x ", opl_ratio);
     uint32_t opl_pos = 0;
@@ -203,7 +205,6 @@ void play_adlib() {
 
     int32_t accum[2] = {0};
     for (;;) {
-
 #if CDROM
         has_cd_samples = cdrom_audio_callback_simple(&cdrom, cd_samples, SAMPLES_PER_BUFFER << 1, true);
 #endif
@@ -221,44 +222,36 @@ void play_adlib() {
                 accum[1] += cd_samples[(i << 1) + 1];
             }
 #endif // CDROM
-                uint32_t opl_index = (opl_pos >> FRAC_BITS);
-                // uint32_t opl_index = i;
-                uint32_t opl_frac = opl_pos & FRAC_MASK;
-                opl_pos += opl_ratio;
-
-                // printf("%x %x\n", opl_index, opl_frac);
-
+            uint32_t opl_index = (opl_pos >> FRAC_BITS);
+            // uint32_t opl_index = i;
+            uint32_t opl_frac = opl_pos & FRAC_MASK;
+            opl_pos += opl_ratio;
 #if !SB_BUFFERLESS // don't support OPL in bufferless for now
-                if (
-                    ((opl_index & SAMPLES_PER_BUFFER) && opl_sample_idx != 0x0) ||
-                    (!(opl_index & SAMPLES_PER_BUFFER) && opl_sample_idx != SAMPLES_PER_BUFFER)
-                ) {
-                    opl_sample_idx = (opl_index + SAMPLES_PER_BUFFER) & SAMPLES_PER_BUFFER;
-                    /*
-                    bool notfirst = false;
-                    while (opl_buffer.tail != opl_buffer.head) {
-                        if (!notfirst) {
+            if (
+                ((opl_index & OPL_SAMPLE_COUNT) && opl_sample_idx != 0x0) ||
+                (!(opl_index & OPL_SAMPLE_COUNT) && opl_sample_idx != OPL_SAMPLE_COUNT)
+            ) {
+                opl_sample_idx = (opl_index + OPL_SAMPLE_COUNT) & OPL_SAMPLE_COUNT;
+                // bool notfirst = false;
+                while (opl_buffer.tail != opl_buffer.head) {
+                    // if (!notfirst) {
 #ifndef PICOW
-                            gpio_xor_mask(LED_PIN);
+                    //     gpio_xor_mask(LED_PIN);
 #endif
-                            notfirst = true;
-                        }
-                        auto cmd = opl_buffer.cmds[opl_buffer.tail];
-                        OPL_Pico_PortWrite((opl_port_t)cmd.addr, cmd.data);
-                        ++opl_buffer.tail;
-                    }
-                    */
-                    OPL_Pico_simple(opl_samples + opl_sample_idx, SAMPLES_PER_BUFFER);
+                    //     notfirst = true;
+                    // }
+                    auto cmd = opl_buffer.cmds[opl_buffer.tail];
+                    OPL_Pico_WriteRegister(cmd.addr, cmd.data);
+                    ++opl_buffer.tail;
                 }
-                int32_t opl_sample = lerp_fixed(
-                    opl_samples[opl_index & 0x1ff],
-                    opl_samples[(opl_index + 1) & 0x1ff],
-                    opl_frac);
-                accum[0] += opl_samples[opl_index & 0x1ff];
-                accum[1] += opl_samples[opl_index & 0x1ff];
-#if CDROM
-            //}
-#endif
+                OPL_Pico_simple(opl_samples + opl_sample_idx, OPL_SAMPLE_COUNT);
+            }
+            int32_t opl_sample = lerp_fixed(
+                opl_samples[opl_index & OPL_BUFFER_BITS],
+                opl_samples[(opl_index + 1) & OPL_BUFFER_BITS],
+                opl_frac);
+            accum[0] += opl_sample;
+            accum[1] += opl_sample;
 #if SOUND_SB
             if (!sb_left) {
                 // putchar('t');