Interference emulation

Cocoa/Document.m

@@ -287,6 +287,7 @@ static void infraredStateChanged(GB_gameboy_t *gb, bool on)
     GB_set_async_input_callback(&gb, (GB_input_callback_t) asyncConsoleInput);
     GB_set_color_correction_mode(&gb, (GB_color_correction_mode_t) [[NSUserDefaults standardUserDefaults] integerForKey:@"GBColorCorrection"]);
     GB_set_light_temperature(&gb, [[NSUserDefaults standardUserDefaults] doubleForKey:@"GBLightTemperature"]);
+    GB_set_interference_volume(&gb, [[NSUserDefaults standardUserDefaults] doubleForKey:@"GBInterferenceVolume"]);
     GB_set_border_mode(&gb, (GB_border_mode_t) [[NSUserDefaults standardUserDefaults] integerForKey:@"GBBorderMode"]);
     [self updatePalette];
     GB_set_rgb_encode_callback(&gb, rgbEncode);
@@ -695,6 +696,11 @@ static unsigned *multiplication_table_for_frequency(unsigned frequency)
                                                  name:@"GBLightTemperatureChanged"
                                                object:nil];
     
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(updateInterferenceVolume)
+                                                 name:@"GBInterferenceVolumeChanged"
+                                               object:nil];
+    
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(updateFrameBlendingMode)
                                                  name:@"GBFrameBlendingModeChanged"
@@ -1848,6 +1854,12 @@ static unsigned *multiplication_table_for_frequency(unsigned frequency)
     }
 }
 
+- (void) updateInterferenceVolume
+{
+    if (GB_is_inited(&gb)) {
+        GB_set_interference_volume(&gb, [[NSUserDefaults standardUserDefaults] doubleForKey:@"GBInterferenceVolume"]);
+    }
+}
 
 - (void) updateFrameBlendingMode
 {

Cocoa/GBPreferencesWindow.h

@@ -18,6 +18,7 @@
 @property (strong) IBOutlet NSPopUpButtonCell *bootROMsButton;
 @property (strong) IBOutlet NSPopUpButton *rumbleModePopupButton;
 @property (weak) IBOutlet NSSlider *temperatureSlider;
+@property (weak) IBOutlet NSSlider *interferenceSlider;
 @property (weak) IBOutlet NSPopUpButton *dmgPopupButton;
 @property (weak) IBOutlet NSPopUpButton *sgbPopupButton;
 @property (weak) IBOutlet NSPopUpButton *cgbPopupButton;

Cocoa/GBPreferencesWindow.m

@@ -27,6 +27,7 @@
     NSPopUpButton *_preferredJoypadButton;
     NSPopUpButton *_rumbleModePopupButton;
     NSSlider *_temperatureSlider;
+    NSSlider *_interferenceSlider;
 }
 
 + (NSArray *)filterList
@@ -108,6 +109,18 @@
 {
     return _temperatureSlider;
 }
+
+- (void)setInterferenceSlider:(NSSlider *)interferenceSlider
+{
+    _interferenceSlider = interferenceSlider;
+    [interferenceSlider setDoubleValue:[[NSUserDefaults standardUserDefaults] doubleForKey:@"GBInterferenceVolume"] * 256];
+}
+
+- (NSSlider *)interferenceSlider
+{
+    return _interferenceSlider;
+}
+
 - (void)setFrameBlendingModePopupButton:(NSPopUpButton *)frameBlendingModePopupButton
 {
     _frameBlendingModePopupButton = frameBlendingModePopupButton;
@@ -303,6 +316,14 @@
     [[NSNotificationCenter defaultCenter] postNotificationName:@"GBLightTemperatureChanged" object:nil];
 }
 
+- (IBAction)volumeTemperatureChanged:(id)sender
+{
+    [[NSUserDefaults standardUserDefaults] setObject:@([sender doubleValue] / 256.0)
+                                              forKey:@"GBInterferenceVolume"];
+    [[NSNotificationCenter defaultCenter] postNotificationName:@"GBInterferenceVolumeChanged" object:nil];
+
+}
+
 - (IBAction)franeBlendingModeChanged:(id)sender
 {
     [[NSUserDefaults standardUserDefaults] setObject:@([sender indexOfSelectedItem])

Cocoa/Preferences.xib

@@ -73,6 +73,7 @@
                 <outlet property="frameBlendingModePopupButton" destination="lxk-db-Sxv" id="wzt-uo-TE6"/>
                 <outlet property="graphicsFilterPopupButton" destination="6pP-kK-EEC" id="LS7-HY-kHC"/>
                 <outlet property="highpassFilterPopupButton" destination="T69-6N-dhT" id="0p6-4m-hb1"/>
+                <outlet property="interferenceSlider" destination="FpE-5i-j5L" id="hfH-e8-7cx"/>
                 <outlet property="playerListButton" destination="gWx-7h-0xq" id="zo6-82-JId"/>
                 <outlet property="preferredJoypadButton" destination="0Az-0R-oNw" id="7JM-tw-BhK"/>
                 <outlet property="rewindPopupButton" destination="7fg-Ww-JjR" id="Ka2-TP-B1x"/>
@@ -174,7 +175,7 @@
                     </textFieldCell>
                 </textField>
                 <popUpButton verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="lxk-db-Sxv">
-                    <rect key="frame" x="32" y="149" width="229" height="22"/>
+                    <rect key="frame" x="30" y="149" width="231" height="22"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <popUpButtonCell key="cell" type="push" title="Disabled" bezelStyle="rounded" alignment="left" lineBreakMode="truncatingTail" state="on" borderStyle="borderAndBezel" imageScaling="proportionallyDown" inset="2" selectedItem="iHP-Yz-fiH" id="aQ6-HN-7Aj">
                         <behavior key="behavior" lightByBackground="YES" lightByGray="YES"/>
@@ -264,7 +265,7 @@
                     </connections>
                 </button>
                 <slider verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="NuA-mL-AJZ">
-                    <rect key="frame" x="32" y="207" width="228" height="24"/>
+                    <rect key="frame" x="30" y="207" width="230" height="24"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <sliderCell key="cell" continuous="YES" state="on" alignment="left" minValue="-256" maxValue="256" tickMarkPosition="below" numberOfTickMarks="3" sliderType="linear" id="KX7-G9-k0O"/>
                     <connections>
@@ -446,11 +447,11 @@
             <point key="canvasLocation" x="-176" y="848"/>
         </customView>
         <customView id="Zn1-Y5-RbR">
-            <rect key="frame" x="0.0" y="0.0" width="292" height="86"/>
+            <rect key="frame" x="0.0" y="0.0" width="292" height="134"/>
             <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
             <subviews>
                 <popUpButton verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="T69-6N-dhT">
-                    <rect key="frame" x="30" y="17" width="233" height="26"/>
+                    <rect key="frame" x="30" y="65" width="233" height="26"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <popUpButtonCell key="cell" type="push" title="Disabled (Keep DC offset)" bezelStyle="rounded" alignment="left" lineBreakMode="truncatingTail" state="on" borderStyle="borderAndBezel" imageScaling="proportionallyDown" inset="2" selectedItem="Fgo-0S-zUG" id="om2-Bn-43B">
                         <behavior key="behavior" lightByBackground="YES" lightByGray="YES"/>
@@ -470,7 +471,7 @@
                     </connections>
                 </popUpButton>
                 <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="WU3-oV-KHO">
-                    <rect key="frame" x="18" y="49" width="256" height="17"/>
+                    <rect key="frame" x="18" y="97" width="256" height="17"/>
                     <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
                     <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" title="High-pass filter:" id="YLF-RL-b2D">
                         <font key="font" metaFont="system"/>
@@ -478,8 +479,25 @@
                         <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
                     </textFieldCell>
                 </textField>
+                <textField horizontalHuggingPriority="251" verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="GPt-9I-QBh">
+                    <rect key="frame" x="18" y="43" width="252" height="17"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <textFieldCell key="cell" scrollable="YES" lineBreakMode="clipping" sendsActionOnEndEditing="YES" title="Interference volume:" id="I2Q-6U-uIx">
+                        <font key="font" metaFont="system"/>
+                        <color key="textColor" name="labelColor" catalog="System" colorSpace="catalog"/>
+                        <color key="backgroundColor" name="controlColor" catalog="System" colorSpace="catalog"/>
+                    </textFieldCell>
+                </textField>
+                <slider verticalHuggingPriority="750" fixedFrame="YES" translatesAutoresizingMaskIntoConstraints="NO" id="FpE-5i-j5L">
+                    <rect key="frame" x="30" y="18" width="232" height="19"/>
+                    <autoresizingMask key="autoresizingMask" flexibleMaxX="YES" flexibleMinY="YES"/>
+                    <sliderCell key="cell" continuous="YES" state="on" alignment="left" maxValue="256" tickMarkPosition="below" sliderType="linear" id="Rbx-DU-xYf"/>
+                    <connections>
+                        <action selector="volumeTemperatureChanged:" target="QvC-M9-y7g" id="HFU-0q-hj1"/>
+                    </connections>
+                </slider>
             </subviews>
-            <point key="canvasLocation" x="-176" y="890"/>
+            <point key="canvasLocation" x="-176" y="914"/>
         </customView>
         <customView id="8TU-6J-NCg">
             <rect key="frame" x="0.0" y="0.0" width="292" height="467"/>

Core/apu.c

@@ -137,6 +137,45 @@ static double smooth(double x)
     return 3*x*x - 2*x*x*x;
 }
 
+static signed interference(GB_gameboy_t *gb)
+{
+    /* These aren't scientifically measured, but based on ear based on several recordings */
+    signed ret = 0;
+    if (gb->halted) {
+        if (gb->model != GB_MODEL_AGB) {
+            ret -= MAX_CH_AMP / 5;
+        }
+        else {
+            ret -= MAX_CH_AMP / 12;
+        }
+    }
+    if (gb->io_registers[GB_IO_LCDC] & 0x80) {
+        ret += MAX_CH_AMP / 7;
+        if ((gb->io_registers[GB_IO_STAT] & 3) == 3 && gb->model != GB_MODEL_AGB) {
+            ret += MAX_CH_AMP / 14;
+        }
+        else if ((gb->io_registers[GB_IO_STAT] & 3) == 1) {
+            ret -= MAX_CH_AMP / 7;
+        }
+    }
+    
+    if (gb->apu.global_enable) {
+        ret += MAX_CH_AMP / 10;
+    }
+    
+    if (GB_is_cgb(gb) && gb->model < GB_MODEL_AGB && (gb->io_registers[GB_IO_RP] & 1)) {
+        ret += MAX_CH_AMP / 10;
+    }
+    
+    if (!GB_is_cgb(gb)) {
+        ret /= 4;
+    }
+    
+    ret += rand() % (MAX_CH_AMP / 12);
+    
+    return ret;
+}
+
 static void render(GB_gameboy_t *gb)
 {
     GB_sample_t output = {0, 0};
@@ -226,6 +265,17 @@ static void render(GB_gameboy_t *gb)
 
     }
     
+    
+    if (gb->apu_output.interference_volume) {
+        signed interference_bias = interference(gb);
+        int16_t interference_sample = (interference_bias - gb->apu_output.interference_highpass);
+        gb->apu_output.interference_highpass = gb->apu_output.interference_highpass * gb->apu_output.highpass_rate +
+        (1 - gb->apu_output.highpass_rate) * interference_sample;
+        interference_bias *= gb->apu_output.interference_volume;
+        
+        filtered_output.left = MAX(MIN(filtered_output.left + interference_bias, 0x7FFF), -0x8000);
+        filtered_output.right = MAX(MIN(filtered_output.right + interference_bias, 0x7FFF), -0x8000);
+    }
     assert(gb->apu_output.sample_callback);
     gb->apu_output.sample_callback(gb, &filtered_output);
 }
@@ -1122,3 +1172,8 @@ void GB_apu_update_cycles_per_sample(GB_gameboy_t *gb)
         gb->apu_output.cycles_per_sample = 2 * GB_get_clock_rate(gb) / (double)gb->apu_output.sample_rate; /* 2 * because we use 8MHz units */
     }
 }
+
+void GB_set_interference_volume(GB_gameboy_t *gb, double volume)
+{
+    gb->apu_output.interference_volume = volume;
+}

Core/apu.h

@@ -154,12 +154,16 @@ typedef struct {
     GB_sample_callback_t sample_callback;
     
     bool rate_set_in_clocks;
+    double interference_volume;
+    double interference_highpass;
 } GB_apu_output_t;
 
 void GB_set_sample_rate(GB_gameboy_t *gb, unsigned sample_rate);
 void GB_set_sample_rate_by_clocks(GB_gameboy_t *gb, double cycles_per_sample); /* Cycles are in 8MHz units */
 void GB_set_highpass_filter_mode(GB_gameboy_t *gb, GB_highpass_mode_t mode);
+void GB_set_interference_volume(GB_gameboy_t *gb, double volume);
 void GB_apu_set_sample_callback(GB_gameboy_t *gb, GB_sample_callback_t callback);
+
 #ifdef GB_INTERNAL
 bool GB_apu_is_DAC_enabled(GB_gameboy_t *gb, unsigned index);
 void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value);

SDL/gui.c

@@ -789,7 +789,7 @@ static const struct menu_item graphics_menu[] = {
     {"Default Window Scale:", cycle_default_scale, current_default_scale, cycle_default_scale_backwards},
     {"Scaling Filter:", cycle_filter, current_filter_name, cycle_filter_backwards},
     {"Color Correction:", cycle_color_correction, current_color_correction_mode, cycle_color_correction_backwards},
-    {"Ambient Light:", decrease_color_temperature, current_color_temperature, increase_color_temperature},
+    {"Ambient Light Temp.:", decrease_color_temperature, current_color_temperature, increase_color_temperature},
     {"Frame Blending:", cycle_blending_mode, blending_mode_string, cycle_blending_mode_backwards},
     {"Mono Palette:", cycle_palette, current_palette, cycle_palette_backwards},
     {"Display Border:", cycle_border_mode, current_border_mode, cycle_border_mode_backwards},
@@ -852,9 +852,33 @@ void decrease_volume(unsigned index)
     }
 }
 
+const char *interference_volume_string(unsigned index)
+{
+    static char ret[5];
+    sprintf(ret, "%d%%", configuration.interference_volume);
+    return ret;
+}
+
+void increase_interference_volume(unsigned index)
+{
+    configuration.interference_volume += 5;
+    if (configuration.interference_volume > 100) {
+        configuration.interference_volume = 100;
+    }
+}
+
+void decrease_interference_volume(unsigned index)
+{
+    configuration.interference_volume -= 5;
+    if (configuration.interference_volume > 100) {
+        configuration.interference_volume = 0;
+    }
+}
+
 static const struct menu_item audio_menu[] = {
     {"Highpass Filter:", cycle_highpass_filter, highpass_filter_string, cycle_highpass_filter_backwards},
     {"Volume:", increase_volume, volume_string, decrease_volume},
+    {"Interference Volume:", increase_interference_volume, interference_volume_string, decrease_interference_volume},
     {"Back", return_to_root_menu},
     {NULL,}
 };

SDL/gui.h

@@ -115,6 +115,7 @@ typedef struct {
     unsigned padding;
     uint8_t color_temperature;
     char bootrom_path[4096];
+    uint8_t interference_volume;
 } configuration_t;
 
 extern configuration_t configuration;

SDL/main.c

@@ -121,6 +121,7 @@ static void open_menu(void)
     }
     GB_set_color_correction_mode(&gb, configuration.color_correction_mode);
     GB_set_light_temperature(&gb, (configuration.color_temperature - 10.0) / 10.0);
+    GB_set_interference_volume(&gb, configuration.interference_volume / 100.0);
     GB_set_border_mode(&gb, configuration.border_mode);
     update_palette();
     GB_set_highpass_filter_mode(&gb, configuration.highpass_mode);
@@ -505,6 +506,7 @@ restart:
         GB_set_sample_rate(&gb, GB_audio_get_frequency());
         GB_set_color_correction_mode(&gb, configuration.color_correction_mode);
         GB_set_light_temperature(&gb, (configuration.color_temperature - 10.0) / 10.0);
+        GB_set_interference_volume(&gb, configuration.interference_volume / 100.0);
         update_palette();
         if ((unsigned)configuration.border_mode <= GB_BORDER_ALWAYS) {
             GB_set_border_mode(&gb, configuration.border_mode);