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Resample rather than call SET_SYSTEM_AV_INFO
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@warmenhoven
warmenhoven committed Jan 24, 2025
1 parent 945fa70 commit 0dce3b1
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Showing 2 changed files with 70 additions and 54 deletions.
2 changes: 2 additions & 0 deletions libretro-build/Makefile.common
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,8 @@ SOURCES_C := $(CORE_DIR)/src/arm/arm.c \
$(CORE_DIR)/src/sm83/sm83.c \
$(CORE_DIR)/src/third-party/inih/ini.c \
$(CORE_DIR)/src/util/audio-buffer.c \
$(CORE_DIR)/src/util/audio-resampler.c \
$(CORE_DIR)/src/util/interpolator.c \
$(CORE_DIR)/src/util/circle-buffer.c \
$(CORE_DIR)/src/util/configuration.c \
$(CORE_DIR)/src/util/formatting.c \
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122 changes: 68 additions & 54 deletions src/platform/libretro/libretro.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,8 @@
#include <mgba/core/log.h>
#include <mgba/core/serialize.h>
#include <mgba/core/version.h>
#include <mgba-util/audio-buffer.h>
#include <mgba-util/audio-resampler.h>
#ifdef M_CORE_GB
#include <mgba/gb/core.h>
#include <mgba/internal/gb/gb.h>
Expand Down Expand Up @@ -41,6 +43,7 @@ FS_Archive sdmcArchive;

#include "libretro_core_options.h"

#define GBA_RESAMPLED_RATE 32768
#define GB_SAMPLES 512
/* An alpha factor of 1/180 is *somewhat* equivalent
* to calculating the average for the last 180
Expand Down Expand Up @@ -82,9 +85,10 @@ static int32_t _readGyroZ(struct mRotationSource* source);

static struct mCore* core;
static mColor* outputBuffer = NULL;
struct mAudioBuffer audioResampleBuffer;
struct mAudioResampler audioResampler;
static int16_t *audioSampleBuffer = NULL;
static size_t audioSampleBufferSize;
static float audioSamplesPerFrameAvg;
static void* data;
static size_t dataSize;
static void* savedata;
Expand Down Expand Up @@ -118,6 +122,7 @@ static unsigned retroAudioBuffOccupancy;
static bool retroAudioBuffUnderrun;
static unsigned retroAudioLatency;
static bool updateAudioLatency;
static bool updateAudioRate;
static bool deferredSetup = false;
static bool useBitmasks = true;
static bool envVarsUpdated;
Expand Down Expand Up @@ -1270,8 +1275,6 @@ static void _doDeferredSetup(void) {
if (!core->loadSave(core, save)) {
save->close(save);
}
stream.audioRateChanged = _audioRateChanged;
_audioRateChanged(NULL, 0);
deferredSetup = false;
}

Expand Down Expand Up @@ -1351,7 +1354,16 @@ void retro_get_system_av_info(struct retro_system_av_info* info) {

info->geometry.aspect_ratio = width / (double) height;
info->timing.fps = core->frequency(core) / (float) core->frameCycles(core);
info->timing.sample_rate = core->audioSampleRate(core);

#ifdef M_CORE_GBA
if (core->platform(core) == mPLATFORM_GBA) {
info->timing.sample_rate = GBA_RESAMPLED_RATE;
} else {
#endif
info->timing.sample_rate = core->audioSampleRate(core);
#ifdef M_CORE_GBA
}
#endif
}

void retro_init(void) {
Expand Down Expand Up @@ -1432,7 +1444,7 @@ void retro_init(void) {
stream.postAudioFrame = NULL;
stream.postAudioBuffer = NULL;
stream.postVideoFrame = NULL;
/*stream.audioRateChanged = _audioRateChanged;*/
stream.audioRateChanged = _audioRateChanged;

imageSource.startRequestImage = _startImage;
imageSource.stopRequestImage = _stopImage;
Expand All @@ -1449,6 +1461,7 @@ void retro_init(void) {
retroAudioBuffUnderrun = false;
retroAudioLatency = 0;
updateAudioLatency = false;
updateAudioRate = false;
}

void retro_deinit(void) {
Expand All @@ -1464,12 +1477,14 @@ void retro_deinit(void) {
_deinitPostProcessing();
#endif

mAudioBufferDeinit(&audioResampleBuffer);
mAudioResamplerDeinit(&audioResampler);

if (audioSampleBuffer) {
free(audioSampleBuffer);
audioSampleBuffer = NULL;
}
audioSampleBufferSize = 0;
audioSamplesPerFrameAvg = 0.0f;

if (sensorStateCallback) {
sensorStateCallback(0, RETRO_SENSOR_ACCELEROMETER_DISABLE, EVENT_RATE);
Expand Down Expand Up @@ -1692,33 +1707,29 @@ void retro_run(void) {
videoCallback(NULL, width, height, VIDEO_WIDTH_MAX * sizeof(mColor));
}

/* Check whether audio sample rate has changed */
if (updateAudioRate) {
struct retro_system_av_info info;
retro_get_system_av_info(&info);
environCallback(RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO, &info);
updateAudioRate = false;
}

#ifdef M_CORE_GBA
if (core->platform(core) == mPLATFORM_GBA) {
struct mAudioBuffer *buffer = core->getAudioBuffer(core);
int samplesAvail = mAudioBufferAvailable(buffer);
if (samplesAvail > 0) {
/* Update 'running average' of number of
* samples per frame.
* Note that this is not a true running
* average, but just a leaky-integrator/
* exponential moving average, used because
* it is simple and fast (i.e. requires no
* window of samples). */
audioSamplesPerFrameAvg = (SAMPLES_PER_FRAME_MOVING_AVG_ALPHA * (float)samplesAvail) +
((1.0f - SAMPLES_PER_FRAME_MOVING_AVG_ALPHA) * audioSamplesPerFrameAvg);
size_t samplesToRead = (size_t)(audioSamplesPerFrameAvg);
/* Resize audio output buffer, if required */
if (audioSampleBufferSize < (samplesToRead * 2)) {
audioSampleBufferSize = (samplesToRead * 2);
audioSampleBuffer = realloc(audioSampleBuffer, audioSampleBufferSize * sizeof(int16_t));
}
int produced = mAudioBufferRead(buffer, audioSampleBuffer, samplesToRead);
if (produced > 0) {
if (audioLowPassEnabled) {
_audioLowPassFilter(audioSampleBuffer, produced);
}
audioCallback(audioSampleBuffer, (size_t)produced);
struct mAudioBuffer *coreBuffer = core->getAudioBuffer(core);
unsigned coreSampleRate = core->audioSampleRate(core);
/* Resample generated audio */
mAudioResamplerSetSource(&audioResampler, coreBuffer, coreSampleRate, true);
mAudioResamplerProcess(&audioResampler);
/* Output resampled audio */
size_t samplesAvail = mAudioBufferAvailable(&audioResampleBuffer);
size_t samplesProduced = mAudioBufferRead(&audioResampleBuffer, audioSampleBuffer, samplesAvail);
if (samplesProduced > 0) {
if (audioLowPassEnabled) {
_audioLowPassFilter(audioSampleBuffer, samplesProduced);
}
audioCallback(audioSampleBuffer, samplesProduced);
}
}
#endif
Expand Down Expand Up @@ -2011,27 +2022,23 @@ bool retro_load_game(const struct retro_game_info* game) {
* audio samples in retro_run() to achieve the
* best possible frame pacing */
if (core->platform(core) == mPLATFORM_GBA) {
/* Set initial output audio buffer size
* to nominal number of samples per frame.
* Buffer will be resized as required in
* retro_run(). */
size_t audioSamplesPerFrame = (size_t)((float) core->audioSampleRate(core) * (float) core->frameCycles(core) /
(float)core->frequency(core));
audioSampleBufferSize = ceil(audioSamplesPerFrame) * 2;
/* Get nominal output samples per frame */
size_t audioSamplesPerFrame = (size_t)(
((float) GBA_RESAMPLED_RATE * (float) core->frameCycles(core) /
(float)core->frequency(core)) + 0.5f);
/* Round up to nearest multiple of 1024
* > This is more than we need, but
* no harm in being safe... */
size_t audioBufferSize = ((audioSamplesPerFrame + 1024 - 1) / 1024) * 1024;
/* Initialise resample buffer */
mAudioBufferInit(&audioResampleBuffer, audioBufferSize, 2);
/* Initialise resampler */
mAudioResamplerInit(&audioResampler, mINTERPOLATOR_SINC);
mAudioResamplerSetDestination(&audioResampler, &audioResampleBuffer, GBA_RESAMPLED_RATE);
/* Initialise output sample buffer
* > Multiply size by 2 (channels) */
audioSampleBufferSize = audioBufferSize * 2;
audioSampleBuffer = malloc(audioSampleBufferSize * sizeof(int16_t));
audioSamplesPerFrameAvg = (float) audioSamplesPerFrame;
/* Internal audio buffer size should be
* audioSamplesPerFrame, but number of samples
* actually generated varies slightly on a
* frame-by-frame basis. We therefore allow
* for some wriggle room by setting double
* what we need (accounting for the hard
* coded blip buffer limit of 0x4000). */
size_t internalAudioBufferSize = audioSamplesPerFrame * 2;
if (internalAudioBufferSize > 0x4000) {
internalAudioBufferSize = 0x4000;
}
core->setAudioBufferSize(core, internalAudioBufferSize);
} else
#endif
{
Expand All @@ -2045,7 +2052,6 @@ bool retro_load_game(const struct retro_game_info* game) {
stream.postAudioBuffer = _postAudioBuffer;
audioSampleBufferSize = GB_SAMPLES * 2;
audioSampleBuffer = malloc(audioSampleBufferSize * sizeof(int16_t));
audioSamplesPerFrameAvg = GB_SAMPLES;
core->setAudioBufferSize(core, GB_SAMPLES);
}

Expand Down Expand Up @@ -2418,9 +2424,17 @@ static void _postAudioBuffer(struct mAVStream* stream, struct mAudioBuffer* buff

static void _audioRateChanged(struct mAVStream* stream, unsigned rate) {
UNUSED(stream);
struct retro_system_av_info info;
retro_get_system_av_info(&info);
environCallback(RETRO_ENVIRONMENT_SET_SYSTEM_AV_INFO, &info);
/* For GBA content, audio is resampled
* to a fixed output rate so internal
* rate changes do not require frontend
* notification */
#ifdef M_CORE_GBA
if (core->platform(core) != mPLATFORM_GBA) {
#endif
updateAudioRate = true;
#ifdef M_CORE_GBA
}
#endif
}

static void _setRumble(struct mRumbleIntegrator* rumble, float level) {
Expand Down

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