5 // (C) 2005-2018 Underground Software
7 // JLH = James Hammons <jlhamm@acm.org>
10 // --- ---------- -----------------------------------------------------------
11 // JLH 12/02/2005 Fixed a problem with sound callback thread signaling the
13 // JLH 12/03/2005 Fixed sound callback dropping samples when the sample
14 // buffer is shorter than the callback sample buffer
19 // - Figure out why it's losing samples (Bard's Tale) [DONE]
20 // - Figure out why it's playing too fast [DONE]
25 #include <string.h> // For memset, memcpy
28 #include "mockingboard.h"
35 #define SAMPLES_PER_FRAME (SAMPLE_RATE / 60.0)
36 #define CYCLES_PER_SAMPLE (1024000.0 / SAMPLE_RATE)
37 // 32K ought to be enough for anybody
38 #define SOUND_BUFFER_SIZE (32768)
45 static SDL_AudioSpec desired, obtained;
46 static SDL_AudioDeviceID device;
47 static bool soundInitialized = false;
48 static bool speakerState = false;
49 static uint16_t soundBuffer[SOUND_BUFFER_SIZE];
50 static uint32_t soundBufferPos;
51 static uint16_t sample;
52 static uint8_t ampPtr = 12; // Start with -2047 - +2047
53 static int16_t amplitude[17] = { 0, 1, 2, 3, 7, 15, 31, 63, 127, 255,
54 511, 1023, 2047, 4095, 8191, 16383, 32767 };
56 // Private function prototypes
58 static void SDLSoundCallback(void * userdata, Uint8 * buffer, int length);
62 N.B: We can convert this from the current callback model to a push model by using SDL_QueueAudio(SDL_AudioDeviceID id, const void * data, Uint32 len) where id is the audio device ID, data is a pointer to the sound buffer, and len is the size of the buffer in *bytes* (not samples!). To use this method, we need to set up things as usual but instead of putting the callback function pointer in desired.callback, we put a NULL there. The downside is that we can't tell if the buffer is being starved or not, which is why we haven't kicked it to the curb just yet--we want to know why we're still getting buffer starvation even if it's not as frequent as it used to be. :-/
63 You can get the size of the audio already queued with SDL_GetQueuedAudioSize(SDL_AudioDeviceID id), which will return the size of the buffer in bytes (again, *not* samples!).
66 // Initialize the SDL sound system
71 desired.freq = SAMPLE_RATE; // SDL will do conversion on the fly, if it can't get the exact rate. Nice!
72 desired.format = AUDIO_U16SYS; // This uses the native endian (for portability)...
74 desired.samples = 512; // Let's try a 1/2K buffer
75 desired.callback = SDLSoundCallback;
77 device = SDL_OpenAudioDevice(NULL, 0, &desired, &obtained, 0);
81 WriteLog("Sound: Failed to initialize SDL sound.\n");
82 WriteLog("SDL sez: %s\n", SDL_GetError());
87 sample = desired.silence; // ? wilwok ? yes
89 SDL_PauseAudioDevice(device, 0);// Start playback!
90 soundInitialized = true;
91 WriteLog("Sound: Successfully initialized.\n");
96 // Close down the SDL sound subsystem
100 if (soundInitialized)
102 SDL_PauseAudioDevice(device, 1);
103 SDL_CloseAudioDevice(device);
104 WriteLog("Sound: Done.\n");
109 void SoundPause(void)
111 if (soundInitialized)
112 SDL_PauseAudioDevice(device, 1);
116 void SoundResume(void)
118 if (soundInitialized)
119 SDL_PauseAudioDevice(device, 0);
124 // Sound card callback handler
126 static uint32_t sndFrmCnt = 0;
127 static uint32_t lastStarve = 0;
128 static void SDLSoundCallback(void * /*userdata*/, Uint8 * buffer8, int length8)
132 // Recast this as a 16-bit type...
133 uint16_t * buffer = (uint16_t *)buffer8;
134 uint32_t length = (uint32_t)length8 / 2;
136 if (soundBufferPos < length)
138 //WriteLog("*** Sound buffer starved (%d short) *** [%d delta %d]\n", length - soundBufferPos, sndFrmCnt, sndFrmCnt - lastStarve);
139 lastStarve = sndFrmCnt;
141 for(uint32_t i=0; i<length; i++)
142 buffer[i] = desired.silence;
144 // The sound buffer is starved...
145 for(uint32_t i=0; i<soundBufferPos; i++)
146 buffer[i] = soundBuffer[i];
148 // Fill buffer with last value
149 for(uint32_t i=soundBufferPos; i<length; i++)
152 // Reset soundBufferPos to start of buffer...
158 // Fill sound buffer with frame buffered sound
159 for(uint32_t i=0; i<length; i++)
160 buffer[i] = soundBuffer[i];
162 soundBufferPos -= length;
164 // Move current buffer down to start
165 for(uint32_t i=0; i<soundBufferPos; i++)
166 soundBuffer[i] = soundBuffer[length + i];
172 // This is called by the main CPU thread every ~21.666 cycles.
174 void WriteSampleToBuffer(void)
176 // uint16_t s1 = AYGetSample(0);
177 // uint16_t s2 = AYGetSample(1);
178 uint16_t s1 = mb[0].ay[0].GetSample();
179 uint16_t s2 = mb[0].ay[1].GetSample();
181 // This should almost never happen, but, if it does...
182 while (soundBufferPos >= (SOUND_BUFFER_SIZE - 1))
184 //WriteLog("WriteSampleToBuffer(): Waiting for sound thread. soundBufferPos=%i, SOUNDBUFFERSIZE-1=%i\n", soundBufferPos, SOUND_BUFFER_SIZE-1);
188 SDL_LockAudioDevice(device);
189 soundBuffer[soundBufferPos++] = sample + s1 + s2;
190 SDL_UnlockAudioDevice(device);
194 void ToggleSpeaker(void)
196 if (!soundInitialized)
199 speakerState = !speakerState;
200 sample = (speakerState ? amplitude[ampPtr] : 0);
206 // Currently set for 16-bit samples
212 void VolumeDown(void)
219 uint8_t GetVolume(void)