Shamusworld >> Repos - apple2/blob - src/sound.cpp

   1 //
   2 // Sound Interface
   3 //
   4 // by James Hammons
   5 // (C) 2005 Underground Software
   6 //
   7 // JLH = James Hammons <jlhamm@acm.org>
   8 //
   9 // WHO  WHEN        WHAT
  10 // ---  ----------  ------------------------------------------------------------
  11 // JLH  12/02/2005  Fixed a problem with sound callback thread signaling the
  12 //                  main thread
  13 // JLH  12/03/2005  Fixed sound callback dropping samples when the sample buffer
  14 //                  is shorter than the callback sample buffer
  15 //
  16
  17 // STILL TO DO:
  18 //
  19 // - Figure out why it's losing samples (Bard's Tale) [DONE]
  20 // - Figure out why it's playing too fast [DONE]
  21 //
  22
  23 #include "sound.h"
  24
  25 #include <string.h>                                                             // For memset, memcpy
  26 #include <SDL2/SDL.h>
  27 #include "log.h"
  28
  29 // Useful defines
  30
  31 //#define DEBUG
  32 //#define WRITE_OUT_WAVE
  33
  34 //#define SAMPLE_RATE                   (44100.0)
  35 #define SAMPLE_RATE                     (48000.0)
  36 #define SAMPLES_PER_FRAME       (SAMPLE_RATE / 60.0)
  37 #define CYCLES_PER_SAMPLE       (1024000.0 / SAMPLE_RATE)
  38 //#define SOUND_BUFFER_SIZE     (8192)
  39 // 32K ought to be enough for anybody
  40 #define SOUND_BUFFER_SIZE       (32768)
  41
  42 // Global variables
  43
  44
  45 // Local variables
  46
  47 static SDL_AudioSpec desired, obtained;
  48 static SDL_AudioDeviceID device;
  49 static bool soundInitialized = false;
  50 static bool speakerState = false;
  51 static int16_t soundBuffer[SOUND_BUFFER_SIZE];
  52 static uint32_t soundBufferPos;
  53 static uint64_t lastToggleCycles;
  54 static SDL_cond * conditional = NULL;
  55 static SDL_mutex * mutex = NULL;
  56 static SDL_mutex * mutex2 = NULL;
  57 static int16_t sample;
  58 static uint8_t ampPtr = 12;                                             // Start with -2047 - +2047
  59 static int16_t amplitude[17] = { 0, 1, 2, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047,
  60         4095, 8191, 16383, 32767 };
  61 #ifdef WRITE_OUT_WAVE
  62 static FILE * fp = NULL;
  63 #endif
  64
  65 // Private function prototypes
  66
  67 static void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
  68
  69
  70 //
  71 // Initialize the SDL sound system
  72 //
  73 void SoundInit(void)
  74 {
  75 #if 0
  76 // To weed out problems for now...
  77 return;
  78 #endif
  79         SDL_zero(desired);
  80         desired.freq = SAMPLE_RATE;                                     // SDL will do conversion on the fly, if it can't get the exact rate. Nice!
  81         desired.format = AUDIO_S16SYS;                          // This uses the native endian (for portability)...
  82         desired.channels = 1;
  83         desired.samples = 512;                                          // Let's try a 1/2K buffer (can always go lower)
  84         desired.callback = SDLSoundCallback;
  85
  86         device = SDL_OpenAudioDevice(NULL, 0, &desired, &obtained, 0);
  87
  88         if (device == 0)
  89         {
  90                 WriteLog("Sound: Failed to initialize SDL sound.\n");
  91                 return;
  92         }
  93
  94         conditional = SDL_CreateCond();
  95         mutex = SDL_CreateMutex();
  96         mutex2 = SDL_CreateMutex();// Let's try real signalling...
  97         soundBufferPos = 0;
  98         lastToggleCycles = 0;
  99         sample = desired.silence;       // ? wilwok ? yes
 100
 101         SDL_PauseAudioDevice(device, 0);                        // Start playback!
 102         soundInitialized = true;
 103         WriteLog("Sound: Successfully initialized.\n");
 104
 105 #ifdef WRITE_OUT_WAVE
 106         fp = fopen("./apple2.wav", "wb");
 107 #endif
 108 }
 109
 110
 111 //
 112 // Close down the SDL sound subsystem
 113 //
 114 void SoundDone(void)
 115 {
 116         if (soundInitialized)
 117         {
 118                 SDL_PauseAudioDevice(device, 1);
 119                 SDL_CloseAudioDevice(device);
 120                 SDL_DestroyCond(conditional);
 121                 SDL_DestroyMutex(mutex);
 122                 SDL_DestroyMutex(mutex2);
 123                 WriteLog("Sound: Done.\n");
 124
 125 #ifdef WRITE_OUT_WAVE
 126                 fclose(fp);
 127 #endif
 128         }
 129 }
 130
 131
 132 void SoundPause(void)
 133 {
 134         if (soundInitialized)
 135                 SDL_PauseAudioDevice(device, 1);
 136 }
 137
 138
 139 void SoundResume(void)
 140 {
 141         if (soundInitialized)
 142                 SDL_PauseAudioDevice(device, 0);
 143 }
 144
 145
 146 //
 147 // Sound card callback handler
 148 //
 149 static void SDLSoundCallback(void * /*userdata*/, Uint8 * buffer8, int length8)
 150 {
 151 //WriteLog("SDLSoundCallback(): begin (soundBufferPos=%i)\n", soundBufferPos);
 152         // The sound buffer should only starve when starting which will cause it to
 153         // lag behind the emulation at most by around 1 frame...
 154         // (Actually, this should never happen since we fill the buffer beforehand.)
 155         // (But, then again, if the sound hasn't been toggled for a while, then this
 156         //  makes perfect sense as the buffer won't have been filled at all!)
 157         // (Should NOT starve now, now that we properly handle frame edges...)
 158
 159         // Let's try using a mutex for shared resource consumption...
 160 //Actually, I think Lock/UnlockAudio() does this already...
 161 //WriteLog("SDLSoundCallback: soundBufferPos = %i\n", soundBufferPos);
 162         SDL_mutexP(mutex2);
 163
 164         // Recast this as a 16-bit type...
 165         int16_t * buffer = (int16_t *)buffer8;
 166         uint32_t length = (uint32_t)length8 / 2;
 167
 168 //WriteLog("SDLSoundCallback(): filling buffer...\n");
 169         if (soundBufferPos < length)
 170         {
 171                 // The sound buffer is starved...
 172                 for(uint32_t i=0; i<soundBufferPos; i++)
 173                         buffer[i] = soundBuffer[i];
 174
 175                 // Fill buffer with last value
 176                 for(uint32_t i=soundBufferPos; i<length; i++)
 177                         buffer[i] = sample;
 178
 179                 // Reset soundBufferPos to start of buffer...
 180                 soundBufferPos = 0;
 181         }
 182         else
 183         {
 184                 // Fill sound buffer with frame buffered sound
 185                 for(uint32_t i=0; i<length; i++)
 186                         buffer[i] = soundBuffer[i];
 187
 188                 soundBufferPos -= length;
 189
 190                 // Move current buffer down to start
 191                 for(uint32_t i=0; i<soundBufferPos; i++)
 192                         soundBuffer[i] = soundBuffer[length + i];
 193         }
 194
 195         // Free the mutex...
 196 //WriteLog("SDLSoundCallback(): SDL_mutexV(mutex2)\n");
 197         SDL_mutexV(mutex2);
 198         // Wake up any threads waiting for the buffer to drain...
 199         SDL_CondSignal(conditional);
 200 //WriteLog("SDLSoundCallback(): end\n");
 201 }
 202
 203
 204 // This is called by the main CPU thread every ~21.333 cycles.
 205 void WriteSampleToBuffer(void)
 206 {
 207 //WriteLog("WriteSampleToBuffer(): SDL_mutexP(mutex2)\n");
 208         SDL_mutexP(mutex2);
 209
 210         // This should almost never happen, but, if it does...
 211         while (soundBufferPos >= (SOUND_BUFFER_SIZE - 1))
 212         {
 213 //WriteLog("WriteSampleToBuffer(): Waiting for sound thread. soundBufferPos=%i, SOUNDBUFFERSIZE-1=%i\n", soundBufferPos, SOUND_BUFFER_SIZE-1);
 214                 SDL_mutexV(mutex2);     // Release it so sound thread can get it,
 215                 SDL_mutexP(mutex);      // Must lock the mutex for the cond to work properly...
 216                 SDL_CondWait(conditional, mutex);       // Sleep/wait for the sound thread
 217                 SDL_mutexV(mutex);      // Must unlock the mutex for the cond to work properly...
 218                 SDL_mutexP(mutex2);     // Re-lock it until we're done with it...
 219         }
 220
 221         soundBuffer[soundBufferPos++] = sample;
 222 //WriteLog("WriteSampleToBuffer(): SDL_mutexV(mutex2)\n");
 223         SDL_mutexV(mutex2);
 224 }
 225
 226
 227 void ToggleSpeaker(void)
 228 {
 229         if (!soundInitialized)
 230                 return;
 231
 232         speakerState = !speakerState;
 233         sample = (speakerState ? amplitude[ampPtr] : -amplitude[ampPtr]);
 234 }
 235
 236
 237 void VolumeUp(void)
 238 {
 239         // Currently set for 16-bit samples
 240         if (ampPtr < 16)
 241                 ampPtr++;
 242 }
 243
 244
 245 void VolumeDown(void)
 246 {
 247         if (ampPtr > 0)
 248                 ampPtr--;
 249 }
 250
 251
 252 uint8_t GetVolume(void)
 253 {
 254         return ampPtr;
 255 }
 256