ref: 38ea875e11a64f5c3ff50fe49bcc70676c542d82
dir: /src/Backends/Audio/SDL2.cpp/
#include "../Audio.h" #include <stddef.h> #include <stdio.h> #include <string> #include "SDL.h" #include "../Misc.h" #include "SoftwareMixer.h" #define MIN(a, b) ((a) < (b) ? (a) : (b)) static SDL_AudioDeviceID device_id; static unsigned long output_frequency; static void (*organya_callback)(void); static unsigned int organya_callback_milliseconds; static void Callback(void *user_data, Uint8 *stream_uint8, int len) { (void)user_data; float *stream = (float*)stream_uint8; unsigned int frames_total = len / sizeof(float) / 2; for (unsigned int i = 0; i < frames_total * 2; ++i) stream[i] = 0.0f; if (organya_callback_milliseconds == 0) { Mixer_MixSounds(stream, frames_total); } else { // Synchronise audio generation with Organya. // In the original game, Organya ran asynchronously in a separate thread, // firing off commands to DirectSound in realtime. To match that, we'd // need a very low-latency buffer, otherwise we'd get mistimed instruments. // Instead, we can just do this. unsigned int frames_done = 0; while (frames_done != frames_total) { static unsigned long organya_countdown; if (organya_countdown == 0) { organya_countdown = (organya_callback_milliseconds * output_frequency) / 1000; // organya_timer is in milliseconds, so convert it to audio frames organya_callback(); } const unsigned int frames_to_do = MIN(organya_countdown, frames_total - frames_done); Mixer_MixSounds(stream + frames_done * 2, frames_to_do); frames_done += frames_to_do; organya_countdown -= frames_to_do; } } } bool AudioBackend_Init(void) { if (SDL_InitSubSystem(SDL_INIT_AUDIO) < 0) { std::string errorMessage = std::string("'SDL_InitSubSystem(SDL_INIT_AUDIO)' failed: ") + SDL_GetError(); Backend_ShowMessageBox("Fatal error (SDL2 audio backend)", errorMessage.c_str()); return false; } Backend_PrintInfo("Available SDL audio drivers:"); for (int i = 0; i < SDL_GetNumAudioDrivers(); ++i) Backend_PrintInfo("%s", SDL_GetAudioDriver(i)); SDL_AudioSpec specification; specification.freq = 48000; specification.format = AUDIO_F32; specification.channels = 2; specification.samples = 0x400; // Roughly 10 milliseconds for 48000Hz specification.callback = Callback; specification.userdata = NULL; SDL_AudioSpec obtained_specification; device_id = SDL_OpenAudioDevice(NULL, 0, &specification, &obtained_specification, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE); if (device_id == 0) { std::string error_message = std::string("'SDL_OpenAudioDevice' failed: ") + SDL_GetError(); Backend_ShowMessageBox("Fatal error (SDL2 audio backend)", error_message.c_str()); return false; } output_frequency = obtained_specification.freq; Mixer_Init(obtained_specification.freq); SDL_PauseAudioDevice(device_id, 0); Backend_PrintInfo("Selected SDL audio driver: %s", SDL_GetCurrentAudioDriver()); return true; } void AudioBackend_Deinit(void) { SDL_CloseAudioDevice(device_id); SDL_QuitSubSystem(SDL_INIT_AUDIO); } AudioBackend_Sound* AudioBackend_CreateSound(unsigned int frequency, const unsigned char *samples, size_t length) { SDL_LockAudioDevice(device_id); Mixer_Sound *sound = Mixer_CreateSound(frequency, samples, length); SDL_UnlockAudioDevice(device_id); return (AudioBackend_Sound*)sound; } void AudioBackend_DestroySound(AudioBackend_Sound *sound) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_DestroySound((Mixer_Sound*)sound); SDL_UnlockAudioDevice(device_id); } void AudioBackend_PlaySound(AudioBackend_Sound *sound, bool looping) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_PlaySound((Mixer_Sound*)sound, looping); SDL_UnlockAudioDevice(device_id); } void AudioBackend_StopSound(AudioBackend_Sound *sound) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_StopSound((Mixer_Sound*)sound); SDL_UnlockAudioDevice(device_id); } void AudioBackend_RewindSound(AudioBackend_Sound *sound) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_RewindSound((Mixer_Sound*)sound); SDL_UnlockAudioDevice(device_id); } void AudioBackend_SetSoundFrequency(AudioBackend_Sound *sound, unsigned int frequency) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_SetSoundFrequency((Mixer_Sound*)sound, frequency); SDL_UnlockAudioDevice(device_id); } void AudioBackend_SetSoundVolume(AudioBackend_Sound *sound, long volume) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_SetSoundVolume((Mixer_Sound*)sound, volume); SDL_UnlockAudioDevice(device_id); } void AudioBackend_SetSoundPan(AudioBackend_Sound *sound, long pan) { if (sound == NULL) return; SDL_LockAudioDevice(device_id); Mixer_SetSoundPan((Mixer_Sound*)sound, pan); SDL_UnlockAudioDevice(device_id); } void AudioBackend_SetOrganyaCallback(void (*callback)(void), unsigned int milliseconds) { SDL_LockAudioDevice(device_id); organya_callback = callback; organya_callback_milliseconds = milliseconds; SDL_UnlockAudioDevice(device_id); }