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

   1 //
   2 // Sound Interface
   3 //
   4 // by James Hammons
   5 // (C) 2014 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 //
  20
  21 #include "sound.h"
  22
  23 #include <string.h>                                                             // For memset, memcpy
  24 #include <SDL2/SDL.h>
  25 #include "log.h"
  26
  27 // Useful defines
  28
  29 //#define DEBUG
  30 //#define WRITE_OUT_WAVE
  31
  32 //#define SAMPLE_RATE                   (44100.0)
  33 #define SAMPLE_RATE                     (48000.0)
  34 #define SAMPLES_PER_FRAME       (SAMPLE_RATE / 60.0)
  35 #define CYCLES_PER_SAMPLE       (1024000.0 / SAMPLE_RATE)
  36 //#define SOUND_BUFFER_SIZE     (8192)
  37 #define SOUND_BUFFER_SIZE       (32768)
  38
  39 // Global variables
  40
  41
  42 // Local variables
  43
  44 static SDL_AudioSpec desired, obtained;
  45 static SDL_AudioDeviceID device;
  46 static bool soundInitialized = false;
  47 static bool speakerState = false;
  48 static int16_t soundBuffer[SOUND_BUFFER_SIZE];
  49 static uint32_t soundBufferPos;
  50 static uint64_t lastToggleCycles;
  51 static SDL_cond * conditional = NULL;
  52 static SDL_mutex * mutex = NULL;
  53 static SDL_mutex * mutex2 = NULL;
  54 static int16_t sample;
  55 static uint8_t ampPtr = 12;                                             // Start with -2047 - +2047
  56 static int16_t amplitude[17] = { 0, 1, 2, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047,
  57         4095, 8191, 16383, 32767 };
  58 #ifdef WRITE_OUT_WAVE
  59 static FILE * fp = NULL;
  60 #endif
  61
  62 // Private function prototypes
  63
  64 static void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
  65
  66
  67 //
  68 // Initialize the SDL sound system
  69 //
  70 void SoundInit(void)
  71 {
  72 #if 0
  73 // To weed out problems for now...
  74 return;
  75 #endif
  76         SDL_zero(desired);
  77         desired.freq = SAMPLE_RATE;                                     // SDL will do conversion on the fly, if it can't get the exact rate. Nice!
  78         desired.format = AUDIO_S16SYS;                          // This uses the native endian (for portability)...
  79         desired.channels = 1;
  80         desired.samples = 512;                                          // Let's try a 1/2K buffer (can always go lower)
  81         desired.callback = SDLSoundCallback;
  82
  83         device = SDL_OpenAudioDevice(NULL, 0, &desired, &obtained, 0);
  84
  85         if (device == 0)
  86         {
  87                 WriteLog("Sound: Failed to initialize SDL sound.\n");
  88                 return;
  89         }
  90
  91         conditional = SDL_CreateCond();
  92         mutex = SDL_CreateMutex();
  93         mutex2 = SDL_CreateMutex();// Let's try real signalling...
  94         soundBufferPos = 0;
  95         lastToggleCycles = 0;
  96         sample = desired.silence;       // ? wilwok ? yes
  97
  98         SDL_PauseAudioDevice(device, 0);                        // Start playback!
  99         soundInitialized = true;
 100         WriteLog("Sound: Successfully initialized.\n");
 101
 102 #ifdef WRITE_OUT_WAVE
 103         fp = fopen("./apple2.wav", "wb");
 104 #endif
 105 }
 106
 107
 108 //
 109 // Close down the SDL sound subsystem
 110 //
 111 void SoundDone(void)
 112 {
 113         if (soundInitialized)
 114         {
 115                 SDL_PauseAudioDevice(device, 1);
 116                 SDL_CloseAudioDevice(device);
 117                 SDL_DestroyCond(conditional);
 118                 SDL_DestroyMutex(mutex);
 119                 SDL_DestroyMutex(mutex2);
 120                 WriteLog("Sound: Done.\n");
 121
 122 #ifdef WRITE_OUT_WAVE
 123                 fclose(fp);
 124 #endif
 125         }
 126 }
 127
 128
 129 void SoundPause(void)
 130 {
 131         if (soundInitialized)
 132                 SDL_PauseAudioDevice(device, 1);
 133 }
 134
 135
 136 void SoundResume(void)
 137 {
 138         if (soundInitialized)
 139                 SDL_PauseAudioDevice(device, 0);
 140 }
 141
 142
 143 //
 144 // Sound card callback handler
 145 //
 146 static void SDLSoundCallback(void * /*userdata*/, Uint8 * buffer8, int length8)
 147 {
 148 //WriteLog("SDLSoundCallback(): begin (soundBufferPos=%i)\n", soundBufferPos);
 149         // The sound buffer should only starve when starting which will cause it to
 150         // lag behind the emulation at most by around 1 frame...
 151         // (Actually, this should never happen since we fill the buffer beforehand.)
 152         // (But, then again, if the sound hasn't been toggled for a while, then this
 153         //  makes perfect sense as the buffer won't have been filled at all!)
 154         // (Should NOT starve now, now that we properly handle frame edges...)
 155
 156         // Let's try using a mutex for shared resource consumption...
 157 //Actually, I think Lock/UnlockAudio() does this already...
 158 //WriteLog("SDLSoundCallback: soundBufferPos = %i\n", soundBufferPos);
 159         SDL_mutexP(mutex2);
 160
 161         // Recast this as a 16-bit type...
 162         int16_t * buffer = (int16_t *)buffer8;
 163         uint32_t length = (uint32_t)length8 / 2;
 164
 165 //WriteLog("SDLSoundCallback(): filling buffer...\n");
 166         if (soundBufferPos < length)
 167         {
 168                 // The sound buffer is starved...
 169                 for(uint32_t i=0; i<soundBufferPos; i++)
 170                         buffer[i] = soundBuffer[i];
 171
 172                 // Fill buffer with last value
 173                 for(uint32_t i=soundBufferPos; i<length; i++)
 174                         buffer[i] = sample;
 175
 176                 // Reset soundBufferPos to start of buffer...
 177                 soundBufferPos = 0;
 178         }
 179         else
 180         {
 181                 // Fill sound buffer with frame buffered sound
 182                 for(uint32_t i=0; i<length; i++)
 183                         buffer[i] = soundBuffer[i];
 184
 185                 soundBufferPos -= length;
 186
 187                 // Move current buffer down to start
 188                 for(uint32_t i=0; i<soundBufferPos; i++)
 189                         soundBuffer[i] = soundBuffer[length + i];
 190         }
 191
 192         // Free the mutex...
 193 //WriteLog("SDLSoundCallback(): SDL_mutexV(mutex2)\n");
 194         SDL_mutexV(mutex2);
 195         // Wake up any threads waiting for the buffer to drain...
 196         SDL_CondSignal(conditional);
 197 //WriteLog("SDLSoundCallback(): end\n");
 198 }
 199
 200
 201 // This is called by the main CPU thread every ~21.333 cycles.
 202 void WriteSampleToBuffer(void)
 203 {
 204 //WriteLog("WriteSampleToBuffer(): SDL_mutexP(mutex2)\n");
 205         SDL_mutexP(mutex2);
 206
 207         // This should almost never happen, but, if it does...
 208         while (soundBufferPos >= (SOUND_BUFFER_SIZE - 1))
 209         {
 210 //WriteLog("WriteSampleToBuffer(): Waiting for sound thread. soundBufferPos=%i, SOUNDBUFFERSIZE-1=%i\n", soundBufferPos, SOUND_BUFFER_SIZE-1);
 211                 SDL_mutexV(mutex2);     // Release it so sound thread can get it,
 212                 SDL_mutexP(mutex);      // Must lock the mutex for the cond to work properly...
 213                 SDL_CondWait(conditional, mutex);       // Sleep/wait for the sound thread
 214                 SDL_mutexV(mutex);      // Must unlock the mutex for the cond to work properly...
 215                 SDL_mutexP(mutex2);     // Re-lock it until we're done with it...
 216         }
 217
 218         soundBuffer[soundBufferPos++] = sample;
 219 //WriteLog("WriteSampleToBuffer(): SDL_mutexV(mutex2)\n");
 220         SDL_mutexV(mutex2);
 221 }
 222
 223
 224 void ToggleSpeaker(void)
 225 {
 226         if (!soundInitialized)
 227                 return;
 228
 229         speakerState = !speakerState;
 230         sample = (speakerState ? amplitude[ampPtr] : -amplitude[ampPtr]);
 231 }
 232
 233
 234 void VolumeUp(void)
 235 {
 236         // Currently set for 16-bit samples
 237         if (ampPtr < 16)
 238                 ampPtr++;
 239 }
 240
 241
 242 void VolumeDown(void)
 243 {
 244         if (ampPtr > 0)
 245                 ampPtr--;
 246 }
 247
 248
 249 uint8_t GetVolume(void)
 250 {
 251         return ampPtr;
 252 }
 253