ref: 81d672e1583e564a798f92c58ac4766af08503e4
dir: /src/Backends/Audio/SDL2.cpp/
#include "../Audio.h"
#include <math.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "SDL.h"
#include "../../Organya.h"
#include "../../WindowsWrapper.h"
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define CLAMP(x, y, z) MIN(MAX((x), (y)), (z))
#ifdef __GNUC__
#define ATTR_HOT __attribute__((hot))
#endif
struct AudioBackend_Sound
{
unsigned char *samples;
size_t frames;
double position;
double advance_delta;
BOOL playing;
BOOL looping;
unsigned int frequency;
float volume;
float pan_l;
float pan_r;
float volume_l;
float volume_r;
struct AudioBackend_Sound *next;
};
static AudioBackend_Sound *sound_list_head;
static SDL_AudioDeviceID device_id;
static unsigned long output_frequency;
static unsigned short organya_timer;
static double MillibelToScale(long volume)
{
// Volume is in hundredths of decibels, from 0 to -10000
volume = CLAMP(volume, -10000, 0);
return pow(10.0, volume / 2000.0);
}
static void SetSoundFrequency(AudioBackend_Sound *sound, unsigned int frequency)
{
sound->frequency = frequency;
sound->advance_delta = (double)frequency / (double)output_frequency;
}
static void SetSoundVolume(AudioBackend_Sound *sound, long volume)
{
sound->volume = (float)MillibelToScale(volume);
sound->volume_l = sound->pan_l * sound->volume;
sound->volume_r = sound->pan_r * sound->volume;
}
static void SetSoundPan(AudioBackend_Sound *sound, long pan)
{
sound->pan_l = (float)MillibelToScale(-pan);
sound->pan_r = (float)MillibelToScale(pan);
sound->volume_l = sound->pan_l * sound->volume;
sound->volume_r = sound->pan_r * sound->volume;
}
// Most CPU-intensive function in the game (2/3rd CPU time consumption in my experience), so marked with attrHot so the compiler considers it a hot spot (as it is) when optimizing
ATTR_HOT static void MixSounds(float *stream, unsigned int frames_total)
{
for (AudioBackend_Sound *sound = sound_list_head; sound != NULL; sound = sound->next)
{
if (sound->playing)
{
float *steam_pointer = stream;
for (unsigned int frames_done = 0; frames_done < frames_total; ++frames_done)
{
// Get two samples, and normalise them to 0-1
const float sample1 = (sound->samples[(size_t)sound->position] - 128.0f) / 128.0f;
const float sample2 = (sound->samples[(size_t)sound->position + 1] - 128.0f) / 128.0f;
// Perform linear interpolation
const float interpolated_sample = sample1 + ((sample2 - sample1) * fmod((float)sound->position, 1.0f));
*steam_pointer++ += interpolated_sample * sound->volume_l;
*steam_pointer++ += interpolated_sample * sound->volume_r;
sound->position += sound->advance_delta;
if (sound->position >= sound->frames)
{
if (sound->looping)
{
sound->position = fmod(sound->position, (double)sound->frames);
}
else
{
sound->playing = FALSE;
sound->position = 0.0;
break;
}
}
}
}
}
}
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_timer == 0)
{
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_timer * output_frequency) / 1000; // organya_timer is in milliseconds, so convert it to audio frames
UpdateOrganya();
}
const unsigned int frames_to_do = MIN(organya_countdown, frames_total - frames_done);
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)
{
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Fatal error (SDL2 audio backend)", "'SDL_InitSubSystem(SDL_INIT_AUDIO)' failed", NULL);
return FALSE;
}
puts("Available SDL2 audio drivers:");
for (int i = 0; i < SDL_GetNumAudioDrivers(); ++i)
puts(SDL_GetAudioDriver(i));
SDL_AudioSpec specification;
specification.freq = 44100;
specification.format = AUDIO_F32;
specification.channels = 2;
specification.samples = 0x400; // Roughly 10 milliseconds for 44100Hz
specification.callback = Callback;
specification.userdata = NULL;
SDL_AudioSpec obtained_specification;
device_id = SDL_OpenAudioDevice(NULL, 0, &specification, &obtained_specification, SDL_AUDIO_ALLOW_FREQUENCY_CHANGE);
output_frequency = obtained_specification.freq;
if (device_id == 0)
{
SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Fatal error (SDL2 audio backend)", "'SDL_OpenAudioDevice' failed", NULL);
return FALSE;
}
SDL_PauseAudioDevice(device_id, 0);
printf("Selected SDL2 audio driver: %s\n", SDL_GetCurrentAudioDriver());
return TRUE;
}
void AudioBackend_Deinit(void)
{
SDL_CloseAudioDevice(device_id);
SDL_QuitSubSystem(SDL_INIT_AUDIO);
}
AudioBackend_Sound* AudioBackend_CreateSound(unsigned int frequency, size_t frames)
{
AudioBackend_Sound *sound = (AudioBackend_Sound*)malloc(sizeof(AudioBackend_Sound));
if (sound == NULL)
return NULL;
sound->samples = (unsigned char*)malloc(frames + 1);
if (sound->samples == NULL)
{
free(sound);
return NULL;
}
sound->frames = frames;
sound->playing = FALSE;
sound->position = 0.0;
SetSoundFrequency(sound, frequency);
SetSoundVolume(sound, 0);
SetSoundPan(sound, 0);
SDL_LockAudioDevice(device_id);
sound->next = sound_list_head;
sound_list_head = sound;
SDL_UnlockAudioDevice(device_id);
return sound;
}
void AudioBackend_DestroySound(AudioBackend_Sound *sound)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
for (AudioBackend_Sound **sound_pointer = &sound_list_head; *sound_pointer != NULL; sound_pointer = &(*sound_pointer)->next)
{
if (*sound_pointer == sound)
{
*sound_pointer = sound->next;
free(sound->samples);
free(sound);
break;
}
}
SDL_UnlockAudioDevice(device_id);
}
unsigned char* AudioBackend_LockSound(AudioBackend_Sound *sound, size_t *size)
{
if (sound == NULL)
return NULL;
SDL_LockAudioDevice(device_id);
if (size != NULL)
*size = sound->frames;
return sound->samples;
}
void AudioBackend_UnlockSound(AudioBackend_Sound *sound)
{
if (sound == NULL)
return;
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_PlaySound(AudioBackend_Sound *sound, BOOL looping)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
sound->playing = TRUE;
sound->looping = looping;
sound->samples[sound->frames] = looping ? sound->samples[0] : 0x80; // For the linear interpolator
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_StopSound(AudioBackend_Sound *sound)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
sound->playing = FALSE;
sound->position = 0.0;
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_RewindSound(AudioBackend_Sound *sound)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
sound->position = 0.0;
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_SetSoundFrequency(AudioBackend_Sound *sound, unsigned int frequency)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
SetSoundFrequency(sound, frequency);
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_SetSoundVolume(AudioBackend_Sound *sound, long volume)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
SetSoundVolume(sound, volume);
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_SetSoundPan(AudioBackend_Sound *sound, long pan)
{
if (sound == NULL)
return;
SDL_LockAudioDevice(device_id);
SetSoundPan(sound, pan);
SDL_UnlockAudioDevice(device_id);
}
void AudioBackend_SetOrganyaTimer(unsigned short timer)
{
SDL_LockAudioDevice(device_id);
organya_timer = timer;
SDL_UnlockAudioDevice(device_id);
}