Fixing audio glitches with wave and noise channels

CMakeLists.txt

@@ -1,6 +1,7 @@
 cmake_minimum_required(VERSION 3.10)
 set(BUILD_SHARED_LIBS OFF)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+set(CMAKE_MSVC_RUNTIME_LIBRARY "MultiThreaded$<$<CONFIG:Debug>:Debug>")
 add_subdirectory(deps/SDL)
 add_subdirectory(deps/SDL_ttf)
 add_subdirectory(deps/portaudio)

include/audio.h

@@ -99,6 +99,24 @@ typedef struct {
 
     u8 wave_ram[16];
 
+    float sq1_history[4410];
+    u32 sq1_index;
+
+    float sq2_history[4410];
+    u32 sq2_index;
+
+    float ch3_history[4410];
+    u32 ch3_index;
+
+    float ch4_history[4410];
+    u32 ch4_index;
+
+    float left_history[4410];
+    u32 left_index;
+
+    float right_history[4410];
+    u32 right_index;
+
 } audio_context;
 
 void audio_init();
@@ -106,4 +124,6 @@ void audio_tick();
 void audio_period_tick();
 
 u8 audio_read(u16 address);
-void audio_write(u16 address, u8 value);
+void audio_write(u16 address, u8 value);
+
+audio_context *audio_get_context();

include/ppu.h

@@ -7,8 +7,6 @@ static const int TICKS_PER_LINE = 456;
 static const int YRES = 144;
 static const int XRES = 160;
 
-static u32 target_frame_time;
-
 bool window_visible();
 
 typedef enum {
@@ -81,6 +79,7 @@ typedef struct {
     u32 *video_buffer;
 
     bool rendering_window;
+    u32 target_frame_time;
 } ppu_context;
 
 void ppu_init();

lib/audio.c

@@ -9,11 +9,17 @@
 #define FRAMES_PER_BUFFER 64
 #define TIME_PER_SAMPLE 1.0f / (SAMPLE_RATE/1000.0f/1000.0f)
 #define TIME_PER_AUDIO_TICK 1.0f / (1048576.0f/1000.0f/1000.0f)
+#define TIME_PER_WAVE_TICK 1.0f / (2097152.0f/1000.0f/1000.0f)
 #define LFSR_BASE_CLOCK 262144.0f
 
 static audio_context ctx;
 
+audio_context *audio_get_context() {
+    return &ctx;
+}
+
 static float audio_time = 0;
+static float wave_time = 0;
 static float lfsr_timer = 0;
 static float lfsr_clock = LFSR_BASE_CLOCK;
 
@@ -81,10 +87,10 @@ static int audio_callback(const void* input_uffer, void *output_buffer,
     float right = 0;
     for(int i = 0; i < framesPerBuffer; i++) {
         audio_time += TIME_PER_SAMPLE;
+        wave_time += TIME_PER_SAMPLE;
         for(;audio_time >= TIME_PER_AUDIO_TICK;audio_time -= TIME_PER_AUDIO_TICK) {
             ctx.sq1_period_timer++;
             ctx.sq2_period_timer++;
-            ctx.ch3_period_timer++;
 
             if(ctx.sq1_period_timer >= 0x800) {
                 ctx.sq1_period_timer = ctx.sq1_period_reset;
@@ -94,6 +100,9 @@ static int audio_callback(const void* input_uffer, void *output_buffer,
                 ctx.sq2_period_timer = ctx.sq2_period_reset;
                 ctx.sq2_sample = (ctx.sq2_sample + 1) % 8;
             }
+        }
+        for(;wave_time >= TIME_PER_WAVE_TICK;wave_time -= TIME_PER_WAVE_TICK) {
+            ctx.ch3_period_timer++;
             if(ctx.ch3_period_timer >= 0x800) {
                 ctx.ch3_period_timer = ctx.ch3_period_reset;
                 ctx.ch3_sample = (ctx.ch3_sample + 1) % 32;
@@ -111,32 +120,39 @@ static int audio_callback(const void* input_uffer, void *output_buffer,
                 u8 new = !((ctx.ch4_lfsr & 0b1) ^ ((ctx.ch4_lfsr >> 1) & 0b1)) & 0b1;
                 ctx.ch4_lfsr |= (new << 15);
                 if(ctx.ch4_lfsr_width) {
+                    ctx.ch4_lfsr &= ~(1 << 7);
                     ctx.ch4_lfsr |= (new << 7);
                 }
                 ctx.ch4_lfsr = ctx.ch4_lfsr >> 1;
                 //printf("lfsr: %02X, bit: %d\n", ctx.ch4_lfsr, new);
             }
         }
+        float sq1_val = 0;
+        float sq2_val = 0;
+        float ch3_val = 0;
+        float ch4_val = 0;
         if(ctx.audio_enabled){
             if(ctx.sq1_enable) {
+                sq1_val = ((float)ctx.sq1_volume/15.0f) * (((float)(square_sample[ctx.sq1_duty][ctx.sq1_sample]) - 7.5f)/7.5f);
                 if(ctx.ch1_left) {
-                    left += ((float)ctx.sq1_volume/15.0f) * (((float)(square_sample[ctx.sq1_duty][ctx.sq1_sample]) - 7.5f)/7.5f);
+                    left += sq1_val;
                 }
                 if(ctx.ch1_right) {
-                    right += ((float)ctx.sq1_volume/15.0f) * (((float)square_sample[ctx.sq1_duty][ctx.sq1_sample] - 7.5f)/7.5f);
+                    right += sq1_val;
                 }
             }
 
             if(ctx.sq2_enable) {
+                sq2_val = ((float)ctx.sq2_volume/15.0f) * (((float)(square_sample[ctx.sq2_duty][ctx.sq2_sample]) - 7.5f)/7.5f);
                 if(ctx.ch2_left) {
-                    left += ((float)ctx.sq2_volume/15.0f) * (((float)(square_sample[ctx.sq2_duty][ctx.sq2_sample]) - 7.5f)/7.5f);
+                    left += sq2_val;
                 }
                 if(ctx.ch2_right) {
-                    right += ((float)ctx.sq2_volume/15.0f) * (((float)(square_sample[ctx.sq2_duty][ctx.sq2_sample]) - 7.5f)/7.5f);
+                    right += sq2_val;
                 }
             }
 
-            if(ctx.ch3_enable && ctx.ch3_volume != 00) {
+            if(ctx.ch3_enable && ctx.ch3_volume != 0x0) {
                 u8 shift = 0;
                 if(ctx.ch3_volume == 0b10) {
                     shift = 1;
@@ -144,25 +160,46 @@ static int audio_callback(const void* input_uffer, void *output_buffer,
                 if(ctx.ch3_volume == 0b11) {
                     shift = 2;
                 }
+                ch3_val = (((float)(ctx.ch3_last_sample >> shift) - 7.5f)/15.0f);
                 if(ctx.ch3_left) {
-                    left += (((float)(ctx.ch3_last_sample >> shift) - 7.5f)/7.5f);
+                    left += ch3_val;
                     //printf("left: %d\n", ctx.ch3_volume);
                 }
                 if(ctx.ch3_right) {
-                    right += (((float)(ctx.ch3_last_sample >> shift) - 7.5f)/7.5f);
+                    right += ch3_val;
                 }
             }
 
             if(ctx.ch4_enable) {
+                ch4_val = ((float)ctx.ch4_volume/15.0f) * ((ctx.ch4_lfsr & 0b1) ? 0 : 1.0f);
                 if(ctx.ch4_left) {
-                    left += ((float)ctx.ch4_volume/15.0f) * (ctx.ch4_lfsr & 0b1);
+                    left += ch4_val;
                     //printf("left: %d\n", ctx.ch3_volume);
                 }
                 if(ctx.ch4_right) {
-                    right += ((float)ctx.ch4_volume/15.0f) * (ctx.ch4_lfsr & 0b1);
+                    right += ch4_val;
                 }
             }
         }
+        ctx.sq1_history[ctx.sq1_index++] = sq1_val;
+        if (ctx.sq1_index == 4410) {
+            ctx.sq1_index = 0;
+        }
+
+        ctx.sq2_history[ctx.sq2_index++] = sq2_val;
+        if (ctx.sq2_index == 4410) {
+            ctx.sq2_index = 0;
+        }
+
+        ctx.ch3_history[ctx.ch3_index++] = ch3_val;
+        if (ctx.ch3_index == 4410) {
+            ctx.ch3_index = 0; 
+        }
+
+        ctx.ch4_history[ctx.ch4_index++] = ch4_val;
+        if (ctx.ch4_index == 4410) {
+            ctx.ch4_index = 0;
+        }
         u8 left_vol = ctx.volume_left == 0 ? 1 : ctx.volume_left;
         u8 right_vol = ctx.volume_right == 0 ? 1 : ctx.volume_right;
         left *= (float)left_vol/7.0f;
@@ -185,6 +222,16 @@ static int audio_callback(const void* input_uffer, void *output_buffer,
             right_cap = right - right_out * 0.996f;
         }
 
+        ctx.left_history[ctx.left_index++] = left_out;
+        if (ctx.left_index == 4410) {
+            ctx.left_index = 0;
+        }
+
+        ctx.right_history[ctx.right_index++] = right_out;
+        if (ctx.right_index == 4410) {
+            ctx.right_index = 0;
+        }
+
         *out++ = left_out;
         *out++ = right_out;
     }
@@ -426,7 +473,7 @@ void enable_wave() {
     }
     ctx.ch3_enable = true;
     ctx.ch3_sample = 0;
-    ctx.ch3_volume = ctx.ch3_initial_volume;
+    //ctx.ch3_volume = ctx.ch3_initial_volume;
     ctx.ch3_period_timer = ctx.ch3_period_reset;
 }
 
@@ -521,7 +568,7 @@ u8 audio_read(u16 address) {
     }
 
     if(address == 0xFF1C) {
-        return ((ctx.ch3_initial_volume & 0b11) << 5) | 0b10011111;
+        return ((ctx.ch3_volume & 0b11) << 5) | 0b10011111;
     }
 
     if(address == 0xFF1D) {
@@ -783,9 +830,10 @@ void audio_write(u16 address, u8 value){
     }
 
     if(address == 0xFF1A) {
-        ctx.ch3_dac = value & 0x80;
+        ctx.ch3_dac = value >> 7;
         if(!ctx.ch3_dac){
             ctx.ch3_enable = false;
+            //printf("ch3 off\n");
         }
     }
     
@@ -796,7 +844,8 @@ void audio_write(u16 address, u8 value){
     }
 
     if(address == 0xFF1C) {
-        ctx.ch3_initial_volume = (value >> 5) & 0b11;
+        ctx.ch3_volume = (value >> 5) & 0b11;
+        //printf("Ch3 vol: %d\n", ctx.ch3_volume);
     }
 
     if(address == 0xFF1D) {
@@ -850,7 +899,7 @@ void audio_write(u16 address, u8 value){
         ctx.ch4_lfsr_width = (value & 0x08);
         ctx.ch4_clock_divider = value & 0b111;
         float div = (ctx.ch4_clock_divider == 0 ? 0.5f : ctx.ch4_clock_divider);
-        float lfsr_rate = (LFSR_BASE_CLOCK) / div * (1 << ctx.ch4_clock_shift);
+        float lfsr_rate = (LFSR_BASE_CLOCK) / (div * (1 << ctx.ch4_clock_shift));
         lfsr_clock = 1.0f / (lfsr_rate/1000.0f/1000.0f);
     }
 

lib/ppu.c

@@ -16,6 +16,7 @@ void ppu_init() {
     ctx.current_frame = 0;
     ctx.line_ticks = 0;
     ctx.video_buffer = malloc(YRES * XRES * sizeof(u32));
+    ctx.target_frame_time = 1000/60;
 
     ctx.pfc.line_x = 0;
     ctx.pfc.pushed_x = 0;

lib/ppu_sm.c

@@ -131,7 +131,6 @@ void ppu_mode_vblank() {
     }
 }
 
-static u32 target_frame_time = 1000/60;
 static long prev_frame_time = 0;
 static long start_timer = 0;
 static long frame_count = 0;
@@ -155,8 +154,8 @@ void ppu_mode_hblank() {
             u32 end = get_ticks();
             u32 frame_time = end - prev_frame_time;
 
-            if(frame_time < target_frame_time) {
+            if(frame_time < ppu_get_context()->target_frame_time) {
-                delay((target_frame_time - frame_time));
+                delay((ppu_get_context()->target_frame_time - frame_time));
             }
 
             if (end - start_timer >= 1000) {

lib/ui.c

@@ -3,6 +3,7 @@
 #include <ppu.h>
 #include <gamepad.h>
 #include <bus.h>
+#include <audio.h>
 
 #include <SDL.h>
 #include <SDL_ttf.h>
@@ -127,10 +128,81 @@ void ui_update() {
             SDL_FillRect(screen, &rc, video_buffer[x + (line_num * XRES)]);
         }
     }
-
     SDL_UpdateTexture(sdlTexture, NULL, screen->pixels, screen->pitch);
     SDL_RenderClear(sdlRenderer);
     SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, NULL);
+    int yOffset = 50;
+    int lastY = (yOffset) + (audio_get_context()->sq1_history[0] * 50);
+    int xOffset = XRES*scale;
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 255, 0, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->sq1_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
+
+    yOffset = 150;
+    lastY = (yOffset) + (audio_get_context()->sq2_history[0] * 50);
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 255, 0, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->sq2_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
+
+    yOffset = 250;
+    lastY = (yOffset) + (audio_get_context()->ch3_history[0] * 50);
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 255, 0, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->ch3_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
+
+    yOffset = 350;
+    lastY = (yOffset) + (audio_get_context()->ch4_history[0] * 50);
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 255, 0, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->ch4_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
+
+    yOffset = 450;
+    lastY = (yOffset) + (audio_get_context()->left_history[0] * 50);
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 0, 255, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->left_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
+
+    yOffset = 550;
+    lastY = (yOffset) + (audio_get_context()->right_history[0] * 50);
+    SDL_SetRenderDrawColor(sdlRenderer, 0, 0, 255, 255);
+    for(int x = 1; x < 882; x++){
+        int y = (yOffset) + (audio_get_context()->right_history[x*5] * 50);
+        SDL_RenderDrawLine(sdlRenderer, x-1+xOffset, lastY, x+xOffset, y);
+        lastY = y;
+        if(x+xOffset == SCREEN_WIDTH) {
+            break;
+        }
+    }
     SDL_RenderPresent(sdlRenderer);
 
     update_debug_window();
@@ -142,11 +214,11 @@ void ui_on_key(bool down, u32 key_code) {
     if(key_code == SDLK_SPACE && down == true) {
         ff = !ff;
         if(ff){
-            target_frame_time = 1000/300;
+            ppu_get_context()->target_frame_time = 1000/300;
         } else {
-            target_frame_time = 1000/60;
+            ppu_get_context()->target_frame_time = 1000/60;
         }
-        printf("target frame time: %d\n", target_frame_time);
+        printf("target frame time: %d\n", ppu_get_context()->target_frame_time);
     }
     switch(key_code){
         case SDLK_z: gamepad_get_state()->b = down; break;