Add APU log to emulator, and VGM output demo

docs/demo.js

@@ -20,6 +20,8 @@ const AUDIO_FRAMES = 4096;
 const AUDIO_LATENCY_SEC = 0.1;
 const MAX_UPDATE_SEC = 5 / 60;
 const CPU_TICKS_PER_SECOND = 4194304;
+const CPU_TICKS_PER_60HZ = Math.floor(CPU_TICKS_PER_SECOND / 60);
+const CPU_TICK_FRACTION_PER_60HZ = CPU_TICKS_PER_SECOND - CPU_TICKS_PER_60HZ * 60;
 const EVENT_NEW_FRAME = 1;
 const EVENT_AUDIO_BUFFER_FULL = 2;
 const EVENT_UNTIL_TICKS = 4;
@@ -76,6 +78,7 @@ let data = {
   cgbColorCurve: 2, // Gambatte/Gameboy Online
   colorOptions: false,
   needsReload: false,
+  recordingVGM: false,
 };
 
 let vm = new Vue({
@@ -141,6 +144,9 @@ let vm = new Vue({
       if (!this.selectedFileHasImage) return '';
       return this.selectedFile.image;
     },
+    vgmLabel: function() {
+      return this.recordingVGM ? 'stop recording VGM' : 'record VGM';
+    },
   },
   watch: {
     paused: function(newPaused, oldPaused) {
@@ -234,9 +240,11 @@ let vm = new Vue({
     downloadSave: async function(file) {
       if (file.extRam) {
         const el = $('#downloadEl');
-        el.href = URL.createObjectURL(file.extRam);
+        const url = URL.createObjectURL(file.extRam);
+        el.href = url;
         el.download = file.name + '.sav';
         el.click();
+        URL.revokeObjectURL(url);
       }
     },
     uploadSaveClicked: function() {
@@ -309,6 +317,23 @@ let vm = new Vue({
       };
       return date.toLocaleDateString(undefined, options);
     },
+    toggleRecordVGM: function() {
+      this.recordingVGM = !this.recordingVGM;
+      if (this.recordingVGM) {
+        emulator.vgmWriter.enabled = true;
+      } else {
+        emulator.vgmWriter.enabled = false;
+        const buffer = emulator.vgmWriter.write();
+        const blob = new Blob([buffer]);
+
+        const el = $('#downloadEl');
+        const url = URL.createObjectURL(blob);
+        el.href = url;
+        el.download = this.loadedFile.name + '.vgm';
+        el.click();
+        URL.revokeObjectURL(url);
+      }
+    },
   }
 });
 
@@ -347,6 +372,7 @@ class Emulator {
     this.video = new Video(module, this.e, $('canvas'));
     this.rewind = new Rewind(module, this.e);
     this.rewindIntervalId = 0;
+    this.vgmWriter = new VGMWriter(module, this.e);
 
     this.lastRafSec = 0;
     this.leftoverTicks = 0;
@@ -476,9 +502,23 @@ class Emulator {
     return this.module._emulator_get_ticks_f64(this.e);
   }
 
-  runUntil(ticks) {
+  getNext60HzTicks(currentTicks) {
+    // Modulus to 1 second.
+    const mod1SecTicks = currentTicks -
+        Math.floor(currentTicks / CPU_TICKS_PER_SECOND) * CPU_TICKS_PER_SECOND;
+    // Round up to next 60Hz interval. Add 1 to ensure we go to the next 60Hz
+    // interval, in case we're on the boundary.
+    const next1SecTicks = Math.ceil(
+        Math.ceil((mod1SecTicks + 1) / CPU_TICKS_PER_60HZ) *
+        CPU_TICKS_PER_60HZ);
+    return currentTicks + (next1SecTicks - mod1SecTicks);
+  }
+
+  runUntil(untilTicks) {
+    let next60hzTicks = this.getNext60HzTicks(this.ticks);
     while (true) {
-      const event = this.module._emulator_run_until_f64(this.e, ticks);
+      const event = this.module._emulator_run_until_f64(
+          this.e, Math.min(untilTicks, next60hzTicks));
       if (event & EVENT_NEW_FRAME) {
         this.rewind.pushBuffer();
         this.video.uploadTexture();
@@ -487,7 +527,13 @@ class Emulator {
         this.audio.pushBuffer();
       }
       if (event & EVENT_UNTIL_TICKS) {
-        break;
+        const currentTicks = this.ticks;
+        if (currentTicks >= next60hzTicks) {  // Hit the 60Hz mark.
+          this.vgmWriter.onFrame();
+          next60hzTicks = this.getNext60HzTicks(currentTicks);
+        } else {  // Ran for the requested time.
+          break;
+        }
       }
     }
     if (this.module._emulator_was_ext_ram_updated(this.e)) {
@@ -1087,3 +1133,76 @@ class Rewind {
     this.statePtr = 0;
   }
 }
+
+class VGMWriter {
+  constructor(module, e) {
+    this.module = module;
+    this.e = e;
+    this.frames = [];
+    this.isEnabled = false;
+  }
+
+  get enabled() {
+    return this.isEnabled;
+  }
+
+  set enabled(set) {
+    this.isEnabled = set;
+    this.module._set_log_apu_writes(this.e, set);
+  }
+
+  onFrame() {
+    if (!this.isEnabled) return;
+    const buffer = makeWasmBuffer(
+        this.module, this.module._get_apu_log_data_ptr(this.e),
+        this.module._get_apu_log_data_size(this.e));
+    const frame = buffer.slice();  // Copy out data.
+    this.frames.push(frame);
+    this.module._reset_apu_log(this.e);
+  }
+
+  write() {
+    // The only commands used are:
+    //   $62:       Wait for 1/60th of a second
+    //   $66:       End of sound data
+    //   $B3 aa dd: Write DMG register
+    const HeaderSize = 256;
+    let size = HeaderSize + 1; // $66 End of sound data
+    for (let frame of this.frames) {
+      // $B3 count
+      size += (frame.length >>> 1) * 3;
+      // $62 count
+      size += 1;
+    }
+    const buffer = new ArrayBuffer(size);
+    const data = new Uint8Array(buffer);
+    const dv = new DataView(buffer);
+    // Write magic
+    data[0] = 0x56;
+    data[1] = 0x67;
+    data[2] = 0x6d;
+    data[3] = 0x20;
+    // Write EOF offset
+    dv.setUint32(0x04, size - 4, true);
+    // Write version 1.61
+    dv.setUint32(0x08, 0x161, true);
+    // Write total # samples (1/60th of a second = 735 samples)
+    dv.setUint32(0x18, this.frames.length * 735, true);
+    // Write offset to data stream
+    dv.setUint32(0x34, HeaderSize - 0x34, true);
+    // Write DMG clock
+    dv.setUint32(0x80, 4194304, true);
+    // Write data stream
+    let offset = HeaderSize;
+    for (let frame of this.frames) {
+      for (let i = 0; i < frame.length; i += 2) {
+        data[offset++] = 0xb3; // DMG write command.
+        data[offset++] = frame[i];
+        data[offset++] = frame[i + 1];
+      }
+      data[offset++] = 0x62; // Frame wait command.
+    }
+    data[offset++] = 0x66; // End of data stream command.
+    return buffer;
+  }
+}

docs/index.html

@@ -213,7 +213,6 @@
             @click="downloadSave(selectedFile)">
           download save
         </button>
-        <a id="downloadEl" hidden download="game.sav"></a>
         <button
             v-bind:disabled="isFilesListEmpty"
             @click="uploadSaveClicked">
@@ -252,6 +251,9 @@
           <input id="colorOptions" v-if="loaded" type="checkbox"
             v-model:checked="colorOptions"></input>
           <label v-if="loaded" for="colorOptions">color options...</label>
+          <button
+              v-show="loaded"
+              @click="toggleRecordVGM">{{vgmLabel}}</button>
         </div>
         <div class="right">
           <span>{{fps.toFixed(1)}}</span> FPS
@@ -287,6 +289,7 @@
         </div>
       </div>
     </div>
+    <a id="downloadEl" hidden download="game.sav"></a>
   </div>
   <script src="sha1.js"></script>
   <script src="binjgb.js"></script>

src/emscripten/exported.json

@@ -4,14 +4,16 @@
 "_emulator_new_simple",
 "_emulator_read_ext_ram",
 "_emulator_run_until_f64",
-"_emulator_set_default_joypad_callback",
 "_emulator_set_builtin_palette",
 "_emulator_set_bw_palette_simple",
+"_emulator_set_default_joypad_callback",
 "_emulator_set_rewind_joypad_callback",
 "_emulator_was_ext_ram_updated",
 "_emulator_write_ext_ram",
 "_ext_ram_file_data_new",
 "_file_data_delete",
+"_get_apu_log_data_ptr",
+"_get_apu_log_data_size",
 "_get_audio_buffer_capacity",
 "_get_audio_buffer_ptr",
 "_get_file_data_ptr",
@@ -22,6 +24,7 @@
 "_get_sgb_frame_buffer_size",
 "_joypad_delete",
 "_joypad_new",
+"_reset_apu_log",
 "_rewind_append",
 "_rewind_begin",
 "_rewind_delete",
@@ -37,4 +40,6 @@
 "_set_joyp_right",
 "_set_joyp_select",
 "_set_joyp_start",
-"_set_joyp_up"]
+"_set_joyp_up",
+"_set_log_apu_writes"
+]

src/emscripten/wrapper.c

@@ -23,6 +23,7 @@ typedef struct {
 
 static Emulator* e;
 
+static EmulatorConfig s_config;
 static EmulatorInit s_init;
 static JoypadButtons s_buttons;
 
@@ -188,3 +189,20 @@ void file_data_delete(FileData* file_data) {
   xfree(file_data->data);
   xfree(file_data);
 }
+
+void set_log_apu_writes(Emulator* e, Bool set) {
+  s_config.log_apu_writes = set;
+  emulator_set_config(e, &s_config);
+}
+
+size_t get_apu_log_data_size(Emulator* e) {
+  ApuLog* apu_log = emulator_get_apu_log(e);
+  return apu_log->write_count * sizeof(apu_log->writes[0]);
+}
+
+void* get_apu_log_data_ptr(Emulator* e) {
+  ApuLog* apu_log = emulator_get_apu_log(e);
+  return &apu_log->writes[0];
+}
+
+void reset_apu_log(Emulator* e) { return emulator_reset_apu_log(e); }

src/emulator.c

@@ -709,6 +709,7 @@ struct Emulator {
   PaletteRGBA pal[PALETTE_TYPE_COUNT];
   PaletteRGBA sgb_pal[4];
   CgbColorCurve cgb_color_curve;
+  ApuLog apu_log;
 };
 
 
@@ -2999,6 +3000,14 @@ static void write_noise_period(Emulator* e) {
 }
 
 static void write_apu(Emulator* e, MaskedAddress addr, u8 value) {
+  if (e->config.log_apu_writes || !APU.initialized) {
+    if (e->apu_log.write_count < MAX_APU_LOG_FRAME_WRITES) {
+      ApuWrite* write = &e->apu_log.writes[e->apu_log.write_count++];
+      write->addr = addr;
+      write->value = value;
+    }
+  }
+
   if (!APU.enabled) {
     if (!IS_CGB && (addr == APU_NR11_ADDR || addr == APU_NR21_ADDR ||
                     addr == APU_NR31_ADDR || addr == APU_NR41_ADDR)) {
@@ -5014,3 +5023,11 @@ void emulator_set_builtin_palette(Emulator* e, u32 index) {
   }
   update_bw_palette_rgba(e, PALETTE_TYPE_BGP);
 }
+
+ApuLog* emulator_get_apu_log(Emulator* e) {
+  return &e->apu_log;
+}
+
+void emulator_reset_apu_log(Emulator* e) {
+  e->apu_log.write_count = 0;
+}

src/emulator.h

@@ -43,6 +43,8 @@ extern "C" {
 #define RGBA_DARK_GRAY 0xff555555u
 #define RGBA_BLACK 0xff000000u
 
+#define MAX_APU_LOG_FRAME_WRITES 1024
+
 typedef struct Emulator Emulator;
 
 enum {
@@ -172,8 +174,19 @@ typedef struct EmulatorConfig {
   Bool disable_window;
   Bool disable_obj;
   Bool allow_simulataneous_dpad_opposites;
+  Bool log_apu_writes;
 } EmulatorConfig;
 
+typedef struct {
+  u8 addr;
+  u8 value;
+} ApuWrite;
+
+typedef struct {
+  ApuWrite writes[MAX_APU_LOG_FRAME_WRITES];
+  size_t write_count;
+} ApuLog;
+
 typedef u32 EmulatorEvent;
 enum {
   EMULATOR_EVENT_NEW_FRAME = 0x1,
@@ -223,6 +236,9 @@ Result emulator_write_ext_ram_to_file(Emulator*, const char* filename);
 EmulatorEvent emulator_step(Emulator*);
 EmulatorEvent emulator_run_until(Emulator*, Ticks until_ticks);
 
+ApuLog* emulator_get_apu_log(Emulator*);
+void emulator_reset_apu_log(Emulator*);
+
 #ifdef __cplusplus
 }
 #endif