ref: e4025e0a6a5e648ff59dd23973c5e7076a07eaa6
dir: /opl/opl_sdl.c/
// Emacs style mode select -*- C++ -*- //----------------------------------------------------------------------------- // // Copyright(C) 2009 Simon Howard // // This program is free software; you can redistribute it and/or // modify it under the terms of the GNU General Public License // as published by the Free Software Foundation; either version 2 // of the License, or (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA // 02111-1307, USA. // // DESCRIPTION: // OPL SDL interface. // //----------------------------------------------------------------------------- #include "config.h" #include <stdio.h> #include <string.h> #include <errno.h> #include <assert.h> #include "SDL.h" #include "SDL_mixer.h" #include "dbopl.h" #include "opl.h" #include "opl_internal.h" #include "opl_queue.h" #define MAX_SOUND_SLICE_TIME 100 /* ms */ typedef struct { unsigned int rate; // Number of times the timer is advanced per sec. unsigned int enabled; // Non-zero if timer is enabled. unsigned int value; // Last value that was set. unsigned int expire_time; // Calculated time that timer will expire. } opl_timer_t; // When the callback mutex is locked using OPL_Lock, callback functions // are not invoked. static SDL_mutex *callback_mutex = NULL; // Queue of callbacks waiting to be invoked. static opl_callback_queue_t *callback_queue; // Mutex used to control access to the callback queue. static SDL_mutex *callback_queue_mutex = NULL; // Current time, in number of samples since startup: static int current_time; // If non-zero, playback is currently paused. static int opl_sdl_paused; // Time offset (in samples) due to the fact that callbacks // were previously paused. static unsigned int pause_offset; // OPL software emulator structure. static Chip opl_chip; // Temporary mixing buffer used by the mixing callback. static int32_t *mix_buffer = NULL; // Register number that was written. static int register_num = 0; // Timers; DBOPL does not do timer stuff itself. static opl_timer_t timer1 = { 12500, 0, 0, 0 }; static opl_timer_t timer2 = { 3125, 0, 0, 0 }; // SDL parameters. static int sdl_was_initialized = 0; static int mixing_freq, mixing_channels; static Uint16 mixing_format; static int SDLIsInitialized(void) { int freq, channels; Uint16 format; return Mix_QuerySpec(&freq, &format, &channels); } // Advance time by the specified number of samples, invoking any // callback functions as appropriate. static void AdvanceTime(unsigned int nsamples) { opl_callback_t callback; void *callback_data; SDL_LockMutex(callback_queue_mutex); // Advance time. current_time += nsamples; if (opl_sdl_paused) { pause_offset += nsamples; } // Are there callbacks to invoke now? Keep invoking them // until there are none more left. while (!OPL_Queue_IsEmpty(callback_queue) && current_time >= OPL_Queue_Peek(callback_queue) + pause_offset) { // Pop the callback from the queue to invoke it. if (!OPL_Queue_Pop(callback_queue, &callback, &callback_data)) { break; } // The mutex stuff here is a bit complicated. We must // hold callback_mutex when we invoke the callback (so that // the control thread can use OPL_Lock() to prevent callbacks // from being invoked), but we must not be holding // callback_queue_mutex, as the callback must be able to // call OPL_SetCallback to schedule new callbacks. SDL_UnlockMutex(callback_queue_mutex); SDL_LockMutex(callback_mutex); callback(callback_data); SDL_UnlockMutex(callback_mutex); SDL_LockMutex(callback_queue_mutex); } SDL_UnlockMutex(callback_queue_mutex); } // Call the OPL emulator code to fill the specified buffer. static void FillBuffer(int16_t *buffer, unsigned int nsamples) { unsigned int i; // This seems like a reasonable assumption. mix_buffer is // 1 second long, which should always be much longer than the // SDL mix buffer. assert(nsamples < mixing_freq); Chip__GenerateBlock2(&opl_chip, nsamples, mix_buffer); // Mix into the destination buffer, doubling up into stereo. for (i=0; i<nsamples; ++i) { buffer[i * 2] = (int16_t) mix_buffer[i]; buffer[i * 2 + 1] = (int16_t) mix_buffer[i]; } } // Callback function to fill a new sound buffer: static void OPL_Mix_Callback(void *udata, Uint8 *byte_buffer, int buffer_bytes) { int16_t *buffer; unsigned int buffer_len; unsigned int filled = 0; // Buffer length in samples (quadrupled, because of 16-bit and stereo) buffer = (int16_t *) byte_buffer; buffer_len = buffer_bytes / 4; // Repeatedly call the OPL emulator update function until the buffer is // full. while (filled < buffer_len) { unsigned int next_callback_time; unsigned int nsamples; SDL_LockMutex(callback_queue_mutex); // Work out the time until the next callback waiting in // the callback queue must be invoked. We can then fill the // buffer with this many samples. if (opl_sdl_paused || OPL_Queue_IsEmpty(callback_queue)) { nsamples = buffer_len - filled; } else { next_callback_time = OPL_Queue_Peek(callback_queue) + pause_offset; nsamples = next_callback_time - current_time; if (nsamples > buffer_len - filled) { nsamples = buffer_len - filled; } } SDL_UnlockMutex(callback_queue_mutex); // Add emulator output to buffer. FillBuffer(buffer + filled * 2, nsamples); filled += nsamples; // Invoke callbacks for this point in time. AdvanceTime(nsamples); } } static void OPL_SDL_Shutdown(void) { Mix_HookMusic(NULL, NULL); if (sdl_was_initialized) { Mix_CloseAudio(); SDL_QuitSubSystem(SDL_INIT_AUDIO); OPL_Queue_Destroy(callback_queue); free(mix_buffer); sdl_was_initialized = 0; } /* if (opl_chip != NULL) { OPLDestroy(opl_chip); opl_chip = NULL; } */ if (callback_mutex != NULL) { SDL_DestroyMutex(callback_mutex); callback_mutex = NULL; } if (callback_queue_mutex != NULL) { SDL_DestroyMutex(callback_queue_mutex); callback_queue_mutex = NULL; } } static unsigned int GetSliceSize(void) { int limit; int n; limit = (opl_sample_rate * MAX_SOUND_SLICE_TIME) / 1000; // Try all powers of two, not exceeding the limit. for (n=0;; ++n) { // 2^n <= limit < 2^n+1 ? if ((1 << (n + 1)) > limit) { return (1 << n); } } // Should never happen? return 1024; } static int OPL_SDL_Init(unsigned int port_base) { // Check if SDL_mixer has been opened already // If not, we must initialize it now if (!SDLIsInitialized()) { if (SDL_Init(SDL_INIT_AUDIO) < 0) { fprintf(stderr, "Unable to set up sound.\n"); return 0; } if (Mix_OpenAudio(opl_sample_rate, AUDIO_S16SYS, 2, GetSliceSize()) < 0) { fprintf(stderr, "Error initialising SDL_mixer: %s\n", Mix_GetError()); SDL_QuitSubSystem(SDL_INIT_AUDIO); return 0; } SDL_PauseAudio(0); // When this module shuts down, it has the responsibility to // shut down SDL. sdl_was_initialized = 1; } else { sdl_was_initialized = 0; } opl_sdl_paused = 0; pause_offset = 0; // Queue structure of callbacks to invoke. callback_queue = OPL_Queue_Create(); current_time = 0; // Get the mixer frequency, format and number of channels. Mix_QuerySpec(&mixing_freq, &mixing_format, &mixing_channels); // Only supports AUDIO_S16SYS if (mixing_format != AUDIO_S16SYS || mixing_channels != 2) { fprintf(stderr, "OPL_SDL only supports native signed 16-bit LSB, " "stereo format!\n"); OPL_SDL_Shutdown(); return 0; } // Mix buffer: mix_buffer = malloc(mixing_freq * sizeof(uint32_t)); // Create the emulator structure: DBOPL_InitTables(); Chip__Chip(&opl_chip); Chip__Setup(&opl_chip, mixing_freq); callback_mutex = SDL_CreateMutex(); callback_queue_mutex = SDL_CreateMutex(); // TODO: This should be music callback? or-? Mix_HookMusic(OPL_Mix_Callback, NULL); return 1; } static unsigned int OPL_SDL_PortRead(opl_port_t port) { unsigned int result = 0; if (timer1.enabled && current_time > timer1.expire_time) { result |= 0x80; // Either have expired result |= 0x40; // Timer 1 has expired } if (timer2.enabled && current_time > timer2.expire_time) { result |= 0x80; // Either have expired result |= 0x20; // Timer 2 has expired } return result; } static void OPLTimer_CalculateEndTime(opl_timer_t *timer) { int tics; // If the timer is enabled, calculate the time when the timer // will expire. if (timer->enabled) { tics = 0x100 - timer->value; timer->expire_time = current_time + (tics * opl_sample_rate) / timer->rate; } } static void WriteRegister(unsigned int reg_num, unsigned int value) { switch (reg_num) { case OPL_REG_TIMER1: timer1.value = value; OPLTimer_CalculateEndTime(&timer1); break; case OPL_REG_TIMER2: timer2.value = value; OPLTimer_CalculateEndTime(&timer2); break; case OPL_REG_TIMER_CTRL: if (value & 0x80) { timer1.enabled = 0; timer2.enabled = 0; } else { if ((value & 0x40) == 0) { timer1.enabled = (value & 0x01) != 0; OPLTimer_CalculateEndTime(&timer1); } if ((value & 0x20) == 0) { timer1.enabled = (value & 0x02) != 0; OPLTimer_CalculateEndTime(&timer2); } } break; default: Chip__WriteReg(&opl_chip, reg_num, value); break; } } static void OPL_SDL_PortWrite(opl_port_t port, unsigned int value) { if (port == OPL_REGISTER_PORT) { register_num = value; } else if (port == OPL_DATA_PORT) { WriteRegister(register_num, value); } } static void OPL_SDL_SetCallback(unsigned int ms, opl_callback_t callback, void *data) { SDL_LockMutex(callback_queue_mutex); OPL_Queue_Push(callback_queue, callback, data, current_time - pause_offset + (ms * mixing_freq) / 1000); SDL_UnlockMutex(callback_queue_mutex); } static void OPL_SDL_ClearCallbacks(void) { SDL_LockMutex(callback_queue_mutex); OPL_Queue_Clear(callback_queue); SDL_UnlockMutex(callback_queue_mutex); } static void OPL_SDL_Lock(void) { SDL_LockMutex(callback_mutex); } static void OPL_SDL_Unlock(void) { SDL_UnlockMutex(callback_mutex); } static void OPL_SDL_SetPaused(int paused) { opl_sdl_paused = paused; } opl_driver_t opl_sdl_driver = { "SDL", OPL_SDL_Init, OPL_SDL_Shutdown, OPL_SDL_PortRead, OPL_SDL_PortWrite, OPL_SDL_SetCallback, OPL_SDL_ClearCallbacks, OPL_SDL_Lock, OPL_SDL_Unlock, OPL_SDL_SetPaused };