Fix audio drift in ntsc/pal composite Closes randyrossi#13

Turns out the Pi's composite out has a vertical refresh rate
_slightly_ greater than 50 or 60 hz.  This was causing too much
audio data to get pushed to the buffer and audio 'drift'
occurred over time.  I ended up timing the actual vertical
refresh rates on composite.  This works for PAL or NTSC
progressive modes for composite.  I haven't tried interlace
to see if that makes a difference.

README.md

@@ -29,7 +29,7 @@ This project uses VICE for emulation without any O/S (Linux) distribution instal
   * http://accentual.com/bmc64
 
 # Timing
-The machine config defaults to PAL 50hz for both HDMI and composite.  You can change this (see below).
+The machine config provided defaults to PAL 50hz for HDMI.  If you want to use composite out, you MUST change the machine_timing parameter in cmdline.txt to 'pal-composite'.  Otherwise, you will have audio synchronization issues.  You can change the machine to be NTSC if you want (see below).
 
 # FileSystem/Drives
 
@@ -135,9 +135,10 @@ Q: Can I switch the machine to NTSC?
 A: Yes, you must edit BOTH config.txt and cmdline.txt.
 
    In config.txt, select an hdmi_mode that is 60hz.
-   In cmdline.txt, change machine_timing to ntsc
+   In cmdline.txt, change machine_timing to ntsc or ntsc-hdmi for HDMI
+   If using composite, machine_timing MUST be ntsc-composite.  Othersie you will get audio synchronization issues.
 
-   Be aware that some demos/games will not run if the machine is NTSC.  If you mix those two settings, your machine will likely run fast/slow and not look good.
+   Be aware that some demos/games will not run if the machine is NTSC.  If you mix those two settings, your machine will likely run fast/slow, not look good or have audio issues (or all of the above).
 
 Q: Why does the video look soft/stretched/dark?
 

cmdline.txt

@@ -1 +1,16 @@
 hide_console=1 fast=true canvas_width=384 canvas_height=272 machine_timing=pal
+
+# Kernel options must appear on a single line separated by spaces.
+#
+# machine_timing
+#
+# For 50hz modes (PAL)
+#    Set to 'pal' or 'pal-hdmi' when using an HDMI display
+#    Set to 'pal-composite' when using the Pi's composite out
+#
+# For 60hz modes (NTSC)
+#    Set to 'ntsc' or 'ntsc-hdmi' when using an HDMI display
+#    Set to 'ntsc-composite' when using the Pi's composite out
+#
+# If you try to use pal or pal-hdmi with composite out, you will get
+# audio synchronization issues with ReSid.

kernel.cpp

@@ -159,6 +159,10 @@ extern "C" {
   void circle_boot_complete() {
      static_kernel->circle_boot_complete();
   }
+
+  int circle_cycles_per_sec() {
+     return static_kernel->circle_cycles_per_second();
+  }
 };
 
 bool CKernel::uiShift = false;
@@ -390,7 +394,8 @@ ViceApp::TShutdownMode CKernel::Run (void)
   // See arch/raspi/videoarch.c
 
   char timing_option[8];
-  if (circle_get_machine_timing() == MACHINE_TIMING_NTSC) {
+  if (circle_get_machine_timing() == MACHINE_TIMING_NTSC_HDMI ||
+      circle_get_machine_timing() == MACHINE_TIMING_NTSC_COMPOSITE) {
      strcpy(timing_option, "-ntsc");
   } else {
      strcpy(timing_option, "-pal");
@@ -442,7 +447,7 @@ ssize_t CKernel::vice_write (int fd, const void * buf, size_t count) {
 }
 
 int CKernel::circle_get_machine_timing () {
-   // Returns 0 for ntsc, 1 for pal
+   // See circle.h for valid values
    return mViceOptions.GetMachineTiming();
 }
 
@@ -858,3 +863,29 @@ void CKernel::circle_lock_release() {
 void CKernel::circle_boot_complete() {
   DisableBootStat();
 }
+
+// 1025700 60hz NTSC hdmi
+// 1022730 59.826hz NTSC composite
+// 982800 50hz for hdmi
+// 985248 50.125hz for composite
+int CKernel::circle_cycles_per_second() {
+   if (circle_get_machine_timing() == MACHINE_TIMING_NTSC_HDMI) {
+      // 60hz
+      return 1025700;
+   } else if (circle_get_machine_timing() == MACHINE_TIMING_NTSC_COMPOSITE) {
+      // Actual C64's NTSC Composite frequency is 59.826 but the Pi's vertical
+      // sync frequency on composite is 60.055. See c64.h for how this is
+      // calculated. This keeps audio buffer to a minimum using ReSid.
+      return 1026640;
+   } else if (circle_get_machine_timing() == MACHINE_TIMING_PAL_HDMI) {
+      // 50hz
+      return 982800;
+   } else if (circle_get_machine_timing() == MACHINE_TIMING_PAL_COMPOSITE) {
+      // Actual C64's PAL Composite frequency is 50.125 but the Pi's vertical
+      // sync frequency on composite is 50.0816. See c64.h for how this is
+      // calculated.  This keep audio buffer to a minimum using ReSid.
+      return 984404;
+   } else {
+      return 982800;
+   }
+}

kernel.h

@@ -87,6 +87,7 @@ class CKernel : public ViceStdioApp
 	void circle_lock_acquire();
 	void circle_lock_release();
 	void circle_boot_complete();
+	int circle_cycles_per_second();
 
 private:
         static bool uiShift;

third_party/vice-3.2/src/arch/raspi/circle.h

@@ -37,6 +37,11 @@
 
 #include <sys/types.h>
 
+#define MACHINE_TIMING_NTSC_HDMI 0
+#define MACHINE_TIMING_PAL_HDMI 1
+#define MACHINE_TIMING_NTSC_COMPOSITE 2
+#define MACHINE_TIMING_PAL_COMPOSITE 3
+
 #define USB_PREF_ANALOG 0
 #define USB_PREF_HAT 1
 

third_party/vice-3.2/src/arch/raspi/menu.c

@@ -844,6 +844,24 @@ void build_menu(struct menu_item* root) {
       strcpy(current_dir_names[i], default_dir_names[i]);
    }
 
+   switch (circle_get_machine_timing()) {
+      case MACHINE_TIMING_NTSC_HDMI:
+         ui_menu_add_button(MENU_TEXT, root, "Timing: NTSC 60Hz HDMI");
+         break;
+      case MACHINE_TIMING_NTSC_COMPOSITE:
+         ui_menu_add_button(MENU_TEXT, root, "Timing: NTSC 60Hz Composite");
+         break;
+      case MACHINE_TIMING_PAL_HDMI:
+         ui_menu_add_button(MENU_TEXT, root, "Timing: PAL 50Hz HDMI");
+         break;
+      case MACHINE_TIMING_PAL_COMPOSITE:
+         ui_menu_add_button(MENU_TEXT, root, "Timing: PAL 50Hz Composite");
+         break;
+      default:
+         ui_menu_add_button(MENU_TEXT, root, "Timing: ERROR");
+         break;
+   }
+
    ui_menu_add_button(MENU_ABOUT, root, "About...");
    ui_menu_add_button(MENU_LICENSE, root, "License...");
 

third_party/vice-3.2/src/arch/raspi/videoarch.c

@@ -281,7 +281,9 @@ void video_arch_canvas_init(struct video_canvas_s *canvas){
   int h = circle_get_display_h();
   bzero(fb, h*fb_pitch);
 
-  if (circle_get_machine_timing() == 0) {
+  int timing = circle_get_machine_timing();
+  if (timing == MACHINE_TIMING_NTSC_HDMI ||
+        timing == MACHINE_TIMING_NTSC_COMPOSITE) {
      canvas->refreshrate = C64_NTSC_RFSH_PER_SEC;
   } else {
      canvas->refreshrate = C64_PAL_RFSH_PER_SEC;
@@ -366,7 +368,7 @@ void videoarch_swap() {
   // Show the region we just drew.
   circle_set_fb_y(video_state.offscreen_buffer_y);
   // Swap buffer ptr for next frame.
-  video_state.offscreen_buffer_y = circle_get_display_h() - 
+  video_state.offscreen_buffer_y = circle_get_display_h() -
                                       video_state.offscreen_buffer_y;
 }
 
@@ -459,7 +461,7 @@ void vsyncarch_postsync(void){
   }
 
   if (raspi_demo_mode) {
-     demo_check();     
+     demo_check();
   }
 }
 

third_party/vice-3.2/src/c64/c64.h

@@ -33,9 +33,16 @@
 #define VICE_C64_H
 
 #ifdef RASPI_COMPILE
-// This is necessary to match the actual ticks we need to simulate
-// between frames. RASPI is tied to vsync which is exactly 50hz.
-#define C64_PAL_CYCLES_PER_SEC  982800
+extern int circle_cycles_per_sec();
+#endif
+
+#ifdef RASPI_COMPILE
+// Raspi needs to change between 50hz and 50.125hz depending on what
+// the user sets in kernel options (cmdline.txt). This this was changed
+// to give results from a function rather than hard coded constant.
+// 982800 // 50hz for hdmi
+// 985248 // 50.125hz for composite
+#define C64_PAL_CYCLES_PER_SEC  (circle_cycles_per_sec())
 #else
 #define C64_PAL_CYCLES_PER_SEC  985248
 #endif
@@ -46,9 +53,12 @@
 #define C64_PAL_RFSH_PER_SEC    (1.0 / ((double)C64_PAL_CYCLES_PER_RFSH / (double)C64_PAL_CYCLES_PER_SEC))
 
 #ifdef RASPI_COMPILE
-// This is necessary to match the actual ticks we need to simulate
-// between frames. RASPI is tied to vsync which is exactly 60hz.
-#define C64_NTSC_CYCLES_PER_SEC  1025700
+// Raspi needs to change between 50hz and 50.125hz depending on what
+// the user sets in kernel options (cmdline.txt). This this was changed
+// to give results from a function rather than hard coded constant.
+// 1025700 60hz NTSC hdmi
+// 1022730 59.826hz NTSC composite
+#define C64_NTSC_CYCLES_PER_SEC  (circle_cycles_per_sec())
 #else
 #define C64_NTSC_CYCLES_PER_SEC  1022730
 #endif

viceapp.h

@@ -68,7 +68,6 @@ class ViceApp
                 {
                         return false;
                 }
-mSerial.Write("here\n",5);
 
                 if (!mInterrupt.Initialize ()) {
 			return false;

viceoptions.cpp

@@ -20,14 +20,18 @@
 #include <string.h>
 #include <stdlib.h>
 
+extern "C" {
+#include "third_party/vice-3.2/src/arch/raspi/circle.h"
+}
+
 #define INVALID_VALUE	((unsigned) -1)
 
 ViceOptions *ViceOptions::s_pThis = 0;
 
 ViceOptions::ViceOptions (void) :
 	m_nCanvasWidth (DEFAULT_CANVAS_WIDTH),
 	m_nCanvasHeight (DEFAULT_CANVAS_HEIGHT),
-	m_nMachineTiming (MACHINE_TIMING_PAL),
+	m_nMachineTiming (MACHINE_TIMING_PAL_HDMI),
 	m_bHideConsole(true),
 	m_bDemoMode(false)
 {
@@ -77,12 +81,16 @@ ViceOptions::ViceOptions (void) :
 		}
 		else if (strcmp (pOption, "machine_timing") == 0)
 		{
-			if (strcmp(pValue, "ntsc") == 0)
-			{
-				m_nMachineTiming = MACHINE_TIMING_NTSC;
-			}
-			else {
-				m_nMachineTiming = MACHINE_TIMING_PAL;
+			if (strcmp(pValue, "ntsc") == 0 ||
+                                strcmp(pValue, "ntsc-hdmi") == 0) {
+				m_nMachineTiming = MACHINE_TIMING_NTSC_HDMI;
+			} else if (strcmp(pValue, "ntsc-composite") == 0) {
+				m_nMachineTiming = MACHINE_TIMING_NTSC_COMPOSITE;
+			} else if (strcmp(pValue, "pal") == 0 ||
+				strcmp(pValue, "pal-hdmi") == 0) {
+				m_nMachineTiming = MACHINE_TIMING_PAL_HDMI;
+			} else if (strcmp(pValue, "pal-composite") == 0) {
+				m_nMachineTiming = MACHINE_TIMING_PAL_COMPOSITE;
 			}
 		}
 		else if (strcmp (pOption, "hide_console") == 0)

viceoptions.h

@@ -22,9 +22,6 @@
 #define DEFAULT_CANVAS_WIDTH 384
 #define DEFAULT_CANVAS_HEIGHT 272
 
-#define MACHINE_TIMING_NTSC 0
-#define MACHINE_TIMING_PAL 1
-
 #define TEST_PIN_TARGET_NONE 0
 #define TEST_PIN_TARGET_SPACE 1
 #define TEST_PIN_TARGET_FIRE_1 2