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Synchronise the audio callback with Organya

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This is the 'perfect' Organya playback I mentioned in the commit
message for 5ea356a3bd
This commit is contained in:
Clownacy 2019-09-09 21:43:33 +00:00
parent a076274864
commit 3eb346ce10
1 changed files with 45 additions and 26 deletions
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71
src/Backends/Audio/SDL2.cpp
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@ -64,32 +64,8 @@ static void SetSoundPan(AudioBackend_Sound *sound, long pan)
sound->volume_r = sound->pan_r * sound->volume;
}
static void Callback(void *user_data, Uint8 *stream_uint8, int len)
static void MixSounds(float *stream, size_t frames_total)
{
(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)
{
static int timer_countdown;
timer_countdown -= frames_total * 1000;
if (timer_countdown <= 0)
{
do
{
timer_countdown += organya_timer * 44100;
UpdateOrganya();
} while (timer_countdown <= 0);
}
}
for (AudioBackend_Sound *sound = sound_list_head; sound != NULL; sound = sound->next)
{
if (sound->playing)
@ -142,6 +118,49 @@ static void Callback(void *user_data, Uint8 *stream_uint8, int len)
}
}
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 * 44100) / 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)
@ -151,7 +170,7 @@ BOOL AudioBackend_Init(void)
specification.freq = 44100;
specification.format = AUDIO_F32;
specification.channels = 2;
specification.samples = 0x200;
specification.samples = 0x400; // Roughly 10 milliseconds
specification.callback = Callback;
specification.userdata = NULL;