Added stereo support. Correct some PCM register behavior.

Cocoa/Document.m

@@ -1,5 +1,5 @@
 #include <CoreAudio/CoreAudio.h>
-#include "AudioClient.h"
+#include "GBAudioClient.h"
 #include "Document.h"
 #include "AppDelegate.h"
 #include "gb.h"
@@ -15,7 +15,7 @@
     NSString *lastConsoleInput;
 }
 
-@property AudioClient *audioClient;
+@property GBAudioClient *audioClient;
 - (void) vblank;
 - (void) log: (const char *) log withAttributes: (gb_log_attributes) attributes;
 - (const char *) getDebuggerInput;
@@ -103,8 +103,7 @@ static uint32_t rgbEncode(GB_gameboy_t *gb, unsigned char r, unsigned char g, un
     gb_set_pixels_output(&gb, self.view.pixels);
     self.view.gb = &gb;
     gb_set_sample_rate(&gb, 96000);
-    self.audioClient = [[AudioClient alloc] initWithRendererBlock:^(UInt32 sampleRate, UInt32 nFrames, SInt16 *buffer) {
+    self.audioClient = [[GBAudioClient alloc] initWithRendererBlock:^(UInt32 sampleRate, UInt32 nFrames, GB_sample_t *buffer) {
-        //apu_render(&gb, sampleRate, nFrames, buffer);
         apu_copy_buffer(&gb, buffer, nFrames);
     } andSampleRate:96000];
     [self.audioClient start];

Cocoa/GBAudioClient.h

@@ -1,11 +1,12 @@
 #import <Foundation/Foundation.h>
+#import "apu.h"
 
-@interface AudioClient : NSObject
+@interface GBAudioClient : NSObject
-@property (strong) void (^renderBlock)(UInt32 sampleRate, UInt32 nFrames, SInt16 *buffer);
+@property (strong) void (^renderBlock)(UInt32 sampleRate, UInt32 nFrames, GB_sample_t *buffer);
 @property (readonly) UInt32 rate;
 @property (readonly, getter=isPlaying) bool playing;
 -(void) start;
 -(void) stop;
--(id) initWithRendererBlock:(void (^)(UInt32 sampleRate, UInt32 nFrames, SInt16 *buffer)) block
+-(id) initWithRendererBlock:(void (^)(UInt32 sampleRate, UInt32 nFrames, GB_sample_t *buffer)) block
               andSampleRate:(UInt32) rate;
 @end

Cocoa/GBAudioClient.m

@@ -1,9 +1,9 @@
 #import <Foundation/Foundation.h>
 #import <AudioToolbox/AudioToolbox.h>
-#import "AudioClient.h"
+#import "GBAudioClient.h"
 
 static OSStatus render(
-                    AudioClient *self,
+                    GBAudioClient *self,
                     AudioUnitRenderActionFlags *ioActionFlags,
                     const AudioTimeStamp *inTimeStamp,
                     UInt32 inBusNumber,
@@ -11,23 +11,19 @@ static OSStatus render(
                     AudioBufferList *ioData)
 
 {
-    // This is a mono tone generator so we only need the first buffer
+    GB_sample_t *buffer = (GB_sample_t *)ioData->mBuffers[0].mData;
-    const int channel = 0;
-    SInt16 *buffer = (SInt16 *)ioData->mBuffers[channel].mData;
-
 
     self.renderBlock(self.rate, inNumberFrames, buffer);
-
     
     return noErr;
 }
 
-@implementation AudioClient
+@implementation GBAudioClient
 {
     AudioComponentInstance audioUnit;
 }
 
--(id) initWithRendererBlock:(void (^)(UInt32 sampleRate, UInt32 nFrames, SInt16 *buffer)) block
+-(id) initWithRendererBlock:(void (^)(UInt32 sampleRate, UInt32 nFrames, GB_sample_t *buffer)) block
               andSampleRate:(UInt32) rate
 {
     if(!(self = [super init]))
@@ -70,10 +66,10 @@ static OSStatus render(
     streamFormat.mFormatID = kAudioFormatLinearPCM;
     streamFormat.mFormatFlags =
     kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;
-    streamFormat.mBytesPerPacket = 2;
+    streamFormat.mBytesPerPacket = 4;
     streamFormat.mFramesPerPacket = 1;
-    streamFormat.mBytesPerFrame = 2;
+    streamFormat.mBytesPerFrame = 4;
-    streamFormat.mChannelsPerFrame = 1;
+    streamFormat.mChannelsPerFrame = 2;
     streamFormat.mBitsPerChannel = 2 * 8;
     err = AudioUnitSetProperty (audioUnit,
                                 kAudioUnitProperty_StreamFormat,

Core/apu.c

@@ -60,10 +60,10 @@ static int16_t step_lfsr(uint16_t lfsr, bool uses_7_bit)
 /* General Todo: The APU emulation seems to fail many accuracy tests. It might require a rewrite with
    these tests in mind. */
 
-void apu_render(GB_gameboy_t *gb, unsigned long sample_rate, unsigned long n_samples, int16_t *samples)
+void apu_render(GB_gameboy_t *gb, unsigned long sample_rate, unsigned long n_samples, GB_sample_t *samples)
 {
     for (; n_samples--; samples++) {
-        *samples = 0;
+        samples->left = samples->right = 0;
         if (!gb->apu.global_enable) {
             continue;
         }
@@ -71,39 +71,45 @@ void apu_render(GB_gameboy_t *gb, unsigned long sample_rate, unsigned long n_sam
         gb->io_registers[GB_IO_PCM_12] = 0;
         gb->io_registers[GB_IO_PCM_34] = 0;
 
-        // Todo: Stereo support
+        {
-
-        if (gb->apu.left_on[0] || gb->apu.right_on[0]) {
             int16_t sample = generate_square(gb->apu.wave_channels[0].phase,
                                              gb->apu.wave_channels[0].amplitude,
                                              gb->apu.wave_channels[0].duty);
-            *samples += sample;
+            if (gb->apu.left_on [0]) samples->left  += sample;
+            if (gb->apu.right_on[0]) samples->right += sample;
             gb->io_registers[GB_IO_PCM_12] = ((int)sample) * 0xF / MAX_CH_AMP;
         }
-        if (gb->apu.left_on[1] || gb->apu.right_on[1]) {
+
+        {
             int16_t sample = generate_square(gb->apu.wave_channels[1].phase,
                                              gb->apu.wave_channels[1].amplitude,
                                              gb->apu.wave_channels[1].duty);
-            *samples += sample;
+            if (gb->apu.left_on [1]) samples->left  += sample;
+            if (gb->apu.right_on[1]) samples->right += sample;
             gb->io_registers[GB_IO_PCM_12] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
         }
-        if (gb->apu.wave_enable && (gb->apu.left_on[2] || gb->apu.right_on[2])) {
+
+        {
             int16_t sample = generate_wave(gb->apu.wave_channels[2].phase,
                                            MAX_CH_AMP,
                                            gb->apu.wave_form,
                                            gb->apu.wave_shift);
-            *samples += sample;
+            if (gb->apu.left_on [2]) samples->left  += sample;
+            if (gb->apu.right_on[2]) samples->right += sample;
             gb->io_registers[GB_IO_PCM_34] = ((int)sample) * 0xF / MAX_CH_AMP;
         }
-        if (gb->apu.left_on[3] || gb->apu.right_on[3]) {
+
+        {
             int16_t sample = generate_noise(gb->apu.wave_channels[3].phase,
                                             gb->apu.wave_channels[3].amplitude,
                                             gb->apu.lfsr);
-            *samples += sample;
+            if (gb->apu.left_on [3]) samples->left  += sample;
+            if (gb->apu.right_on[3]) samples->right += sample;
             gb->io_registers[GB_IO_PCM_34] |= (((int)sample) * 0xF / MAX_CH_AMP) << 4;
         }
 
-        *samples *= gb->apu.left_volume;
+        samples->left *= gb->apu.left_volume;
+        samples->right *= gb->apu.right_volume;
 
         for (unsigned char i = 0; i < 4; i++) {
             /* Phase */
@@ -168,7 +174,7 @@ void apu_run(GB_gameboy_t *gb)
     while (gb->audio_copy_in_progress);
     double ticks_per_sample = (double) CPU_FREQUENCY / gb->sample_rate;
     while (gb->apu_cycles > ticks_per_sample) {
-        int16_t sample = 0;
+        GB_sample_t sample = {0, };
         apu_render(gb, gb->sample_rate, 1, &sample);
         gb->apu_cycles -= ticks_per_sample;
         if (gb->audio_position == gb->buffer_size) {
@@ -186,7 +192,7 @@ void apu_run(GB_gameboy_t *gb)
     }
 }
 
-void apu_copy_buffer(GB_gameboy_t *gb, int16_t *dest, unsigned int count)
+void apu_copy_buffer(GB_gameboy_t *gb, GB_sample_t *dest, unsigned int count)
 {
     gb->audio_copy_in_progress = true;
 
@@ -198,11 +204,11 @@ void apu_copy_buffer(GB_gameboy_t *gb, int16_t *dest, unsigned int count)
 
     if (count > gb->audio_position) {
         // gb_log(gb, "Audio underflow: %d\n", count - gb->audio_position);
-        memset(dest + gb->audio_position, 0, (count - gb->audio_position) * 2);
+        memset(dest + gb->audio_position, 0, (count - gb->audio_position) * sizeof(*gb->audio_buffer));
         count = gb->audio_position;
     }
-    memcpy(dest, gb->audio_buffer, count * 2);
+    memcpy(dest, gb->audio_buffer, count * sizeof(*gb->audio_buffer));
-    memmove(gb->audio_buffer, gb->audio_buffer + count, (gb->audio_position - count) * 2);
+    memmove(gb->audio_buffer, gb->audio_buffer + count, (gb->audio_position - count) * sizeof(*gb->audio_buffer));
     gb->audio_position -= count;
 
     gb->audio_copy_in_progress = false;

Core/apu.h

@@ -11,6 +11,12 @@
 struct GB_gameboy_s;
 typedef struct GB_gameboy_s GB_gameboy_t;
 
+typedef struct
+{
+    int16_t left;
+    int16_t right;
+} GB_sample_t;
+
 /* Not all used on all channels */
 typedef struct
 {
@@ -48,12 +54,11 @@ typedef struct
     bool global_enable;
 } GB_apu_t;
 
-void apu_render(GB_gameboy_t *gb, unsigned long sample_rate, unsigned long n_samples, int16_t *samples);
+void apu_render(GB_gameboy_t *gb, unsigned long sample_rate, unsigned long n_samples, GB_sample_t *samples);
-void apu_copy_buffer(GB_gameboy_t *gb, int16_t *dest, unsigned int count);
+void apu_copy_buffer(GB_gameboy_t *gb, GB_sample_t *dest, unsigned int count);
 void apu_write(GB_gameboy_t *gb, unsigned char reg, unsigned char value);
 unsigned char apu_read(GB_gameboy_t *gb, unsigned char reg);
 void apu_init(GB_gameboy_t *gb);
-void apu_copy_buffer(GB_gameboy_t *gb, int16_t *dest, unsigned int count);
 void apu_run(GB_gameboy_t *gb);
 
 #endif /* apu_h */

Core/gb.c

@@ -445,7 +445,7 @@ void gb_set_sample_rate(GB_gameboy_t *gb, unsigned int sample_rate)
         free(gb->audio_buffer);
     }
     gb->buffer_size = sample_rate / 25; // 40ms delay
-    gb->audio_buffer = malloc(gb->buffer_size * 2);
+    gb->audio_buffer = malloc(gb->buffer_size * sizeof(*gb->audio_buffer));
     gb->sample_rate = sample_rate;
     gb->audio_position = 0;
 }

Core/gb.h

@@ -239,7 +239,7 @@ typedef struct GB_gameboy_s{
 
     /* APU */
     GB_apu_t apu;
-    int16_t *audio_buffer;
+    GB_sample_t *audio_buffer;
     unsigned int buffer_size;
     unsigned int sample_rate;
     unsigned int audio_position;

SDL/main.c

@@ -136,7 +136,7 @@ static void debugger_interrupt(int ignore)
 
 static void audio_callback(void *gb, Uint8 *stream, int len)
 {
-    apu_copy_buffer(gb, (int16_t *) stream, len / sizeof(int16_t));
+    apu_copy_buffer(gb, (GB_sample_t *) stream, len / sizeof(GB_sample_t));
 }
 
 #ifdef __APPLE__
@@ -206,7 +206,7 @@ usage:
     SDL_memset(&want, 0, sizeof(want));
     want.freq = 96000;
     want.format = AUDIO_S16SYS;
-    want.channels = 1;
+    want.channels = 2;
     want.samples = 512;
     want.callback = audio_callback;
     want.userdata = &gb;