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Output 32-bit float samples to preserve dynamic range and prevent clipping #59

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Output 32-bit float samples to preserve dynamic range and prevent clipping #59

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f1b19f7
Output 32-bit float samples to preserve dynamic range and prevent cli…
Falcosoft Apr 24, 2024
3a09aca
Optimized process/thread priority for Windows
Falcosoft Apr 24, 2024
291e150
simpler int to float conversion
Falcosoft Apr 24, 2024
5f39d06
separated audio callbacks for short/float types
Falcosoft Apr 24, 2024
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123 changes: 94 additions & 29 deletions src/mcu.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,11 @@
#include "utf8main.h"
#include "utils/files.h"

#ifdef _WIN32
#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#endif

#if __linux__
#include <unistd.h>
#include <limits.h>
Expand Down Expand Up @@ -105,7 +110,8 @@ static const int ROMSM_SIZE = 0x1000;

static int audio_buffer_size;
static int audio_page_size;
static short *sample_buffer;
static short *sample_buffer = nullptr;
static float *sample_buffer_float = nullptr;

static int sample_read_ptr;
static int sample_write_ptr;
Expand Down Expand Up @@ -924,6 +930,11 @@ void MCU_WorkThread_Unlock(void)

int SDLCALL work_thread(void* data)
{

#ifdef _WIN32
SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_HIGHEST);
#endif

work_thread_lock = SDL_CreateMutex();

MCU_WorkThread_Lock();
Expand Down Expand Up @@ -1079,12 +1090,21 @@ void unscramble(uint8_t *src, uint8_t *dst, int len)
}
}

void audio_callback(void* /*userdata*/, Uint8* stream, int len)
{
len /= 2;
memcpy(stream, &sample_buffer[sample_read_ptr], len * 2);
memset(&sample_buffer[sample_read_ptr], 0, len * 2);
sample_read_ptr += len;
void audio_callback_short(void* /*userdata*/, Uint8* stream, int len)
{
memcpy(stream, &sample_buffer[sample_read_ptr], len);
memset(&sample_buffer[sample_read_ptr], 0, len);
sample_read_ptr += len / sizeof(short);

sample_read_ptr %= audio_buffer_size;
}

void audio_callback_float(void* /*userdata*/, Uint8* stream, int len)
{
memcpy(stream, &sample_buffer_float[sample_read_ptr], len);
memset(&sample_buffer_float[sample_read_ptr], 0, len);
sample_read_ptr += len / sizeof(float);

sample_read_ptr %= audio_buffer_size;
}

Expand Down Expand Up @@ -1116,22 +1136,36 @@ static const char* audio_format_to_str(int format)
return "UNK";
}

int MCU_OpenAudio(int deviceIndex, int pageSize, int pageNum)
enum class AudioFormat {
INT16,
FLOAT32,
};

int MCU_OpenAudio(int deviceIndex, int pageSize, int pageNum, AudioFormat audioFormat)
{
SDL_AudioSpec spec = {};
SDL_AudioSpec spec_actual = {};

audio_page_size = (pageSize/2)*2; // must be even
audio_buffer_size = audio_page_size*pageNum;
audio_page_size = (pageSize / 2) * 2; // must be even
audio_buffer_size = audio_page_size * pageNum;

spec.format = AUDIO_S16SYS;
spec.format = audioFormat == AudioFormat::INT16 ? AUDIO_S16SYS : AUDIO_F32SYS;
spec.freq = (mcu_mk1 || mcu_jv880) ? 64000 : 66207;
spec.channels = 2;
spec.callback = audio_callback;
spec.channels = 2;
spec.samples = audio_page_size / 4;

sample_buffer = (short*)calloc(audio_buffer_size, sizeof(short));
if (!sample_buffer)
if (audioFormat == AudioFormat::INT16)
{
spec.callback = audio_callback_short;
sample_buffer = (short*)calloc(audio_buffer_size, sizeof(short));
}
else if (audioFormat == AudioFormat::FLOAT32)
{
spec.callback = audio_callback_float;
sample_buffer_float = (float*)calloc(audio_buffer_size, sizeof(float));
}

if (!sample_buffer && !sample_buffer_float)
{
printf("Cannot allocate audio buffer.\n");
return 0;
Expand Down Expand Up @@ -1184,22 +1218,33 @@ void MCU_CloseAudio(void)
{
SDL_CloseAudio();
if (sample_buffer) free(sample_buffer);
else if (sample_buffer_float) free(sample_buffer_float);
}

void MCU_PostSample(int *sample)
{
sample[0] >>= 15;
if (sample[0] > INT16_MAX)
sample[0] = INT16_MAX;
else if (sample[0] < INT16_MIN)
sample[0] = INT16_MIN;
sample[1] >>= 15;
if (sample[1] > INT16_MAX)
sample[1] = INT16_MAX;
else if (sample[1] < INT16_MIN)
sample[1] = INT16_MIN;
sample_buffer[sample_write_ptr + 0] = sample[0];
sample_buffer[sample_write_ptr + 1] = sample[1];
if (sample_buffer)
{
sample[0] >>= 15;
if (sample[0] > INT16_MAX)
sample[0] = INT16_MAX;
else if (sample[0] < INT16_MIN)
sample[0] = INT16_MIN;
sample[1] >>= 15;
if (sample[1] > INT16_MAX)
sample[1] = INT16_MAX;
else if (sample[1] < INT16_MIN)
sample[1] = INT16_MIN;
sample_buffer[sample_write_ptr + 0] = sample[0];
sample_buffer[sample_write_ptr + 1] = sample[1];
}
else if (sample_buffer_float)
{
const float divRec = 1 / 536870912.0f;
sample_buffer_float[sample_write_ptr + 0] = sample[0] * divRec;
sample_buffer_float[sample_write_ptr + 1] = sample[1] * divRec;
}

sample_write_ptr = (sample_write_ptr + 2) % audio_buffer_size;
}

Expand Down Expand Up @@ -1250,6 +1295,7 @@ enum class ResetType {
GM_RESET,
};


void MIDI_Reset(ResetType resetType)
{
const unsigned char gmReset[] = { 0xF0, 0x7E, 0x7F, 0x09, 0x01, 0xF7 };
Expand Down Expand Up @@ -1277,16 +1323,23 @@ int main(int argc, char *argv[])
(void)argc;
std::string basePath;

#ifdef _WIN32
SetPriorityClass(GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS);
#endif

int port = 0;
int audioDeviceIndex = -1;
int pageSize = 512;
int pageNum = 32;
bool autodetect = true;
ResetType resetType = ResetType::NONE;
AudioFormat audioFormat = AudioFormat::INT16;

romset = ROM_SET_MK2;

{
bool isBufferSet = false;

for (int i = 1; i < argc; i++)
{
if (!strncmp(argv[i], "-p:", 3))
Expand All @@ -1297,6 +1350,10 @@ int main(int argc, char *argv[])
{
audioDeviceIndex = atoi(argv[i] + 3);
}
else if (!strcmp(argv[i], "-af"))
{
audioFormat = AudioFormat::FLOAT32;
}
else if (!strncmp(argv[i], "-ab:", 4))
{
char* pColon = argv[i] + 3;
Expand All @@ -1308,6 +1365,7 @@ int main(int argc, char *argv[])
if (pColon && pColon[1] != 0)
{
pageNum = atoi(++pColon);
isBufferSet = true;
}
}

Expand All @@ -1316,6 +1374,7 @@ int main(int argc, char *argv[])
{
pageSize = 512;
pageNum = 32;
isBufferSet = false;
}
}
else if (!strcmp(argv[i], "-mk2"))
Expand Down Expand Up @@ -1350,7 +1409,13 @@ int main(int argc, char *argv[])
else if (!strcmp(argv[i], "-gm"))
{
resetType = ResetType::GM_RESET;
}
}
}

if (audioFormat == AudioFormat::FLOAT32 && !isBufferSet)
{
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Maybe this flag would be not needed if you move the pageSize,pageNum set to inside the else if (!strcmp(argv[i], "-af")) if case?

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@Falcosoft Falcosoft Apr 24, 2024 •
edited
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In that case the argument order would be mandatory otherwise at
(!strcmp(argv[i], "-af")) you cannot know if -ab is set before, not set at all or only will be set after -af.
The if (audioFormat == AudioFormat::FLOAT32 && !isBufferSet) check is added to make sure that only change the dafault if -ab is not set manually.
But correct me if I'm wrong, maybe I overlook something.

pageSize = 6144;
pageNum = 3;
}
}

Expand Down Expand Up @@ -1582,7 +1647,7 @@ int main(int argc, char *argv[])
return 2;
}

if (!MCU_OpenAudio(audioDeviceIndex, pageSize, pageNum))
if (!MCU_OpenAudio(audioDeviceIndex, pageSize, pageNum, audioFormat))
{
fprintf(stderr, "FATAL ERROR: Failed to open the audio stream.\n");
fflush(stderr);
Expand Down