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Web Audio: Experimental loopback support.

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This uses `getDisplayMedia()`. Support for this is extremely browser and
system specific so I'm not advertising support for this documentation.

Public issue https://github.com/mackron/miniaudio/issues/967
This commit is contained in:
David Reid
2026-01-21 12:18:42 +10:00
parent f6b973d384
commit ba963e46b5
2 changed files with 156 additions and 34 deletions
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tests/emscripten/emscripten.c
+94 -6
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@@ -22,9 +22,8 @@ ma_waveform sineWave; /* For playback example. */
void main_loop__em(void* pUserData)
{
ma_device* pDevice = (ma_device*)pUserData;
if (ma_device_get_threading_mode(pDevice) == MA_THREADING_MODE_SINGLE_THREADED) {
ma_device_step(pDevice, MA_BLOCKING_MODE_NON_BLOCKING);
if (threadingMode == MA_THREADING_MODE_SINGLE_THREADED) {
ma_device_step((ma_device*)pUserData, MA_BLOCKING_MODE_NON_BLOCKING);
}
}
@@ -97,7 +96,6 @@ static void do_duplex()
deviceConfig.capture.pDeviceID = NULL;
deviceConfig.capture.format = DEVICE_FORMAT;
deviceConfig.capture.channels = 2;
deviceConfig.capture.shareMode = ma_share_mode_shared;
deviceConfig.playback.pDeviceID = NULL;
deviceConfig.playback.format = DEVICE_FORMAT;
deviceConfig.playback.channels = 2;
@@ -117,13 +115,102 @@ static void do_duplex()
}
ma_device loopbackPlaybackDevice;
ma_pcm_rb loopbackRB;
void data_callback_loopback_capture(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
{
ma_uint32 framesToWrite;
void* pBuffer;
(void)pDevice;
(void)pOutput;
/* Write to the ring buffer. */
framesToWrite = frameCount;
ma_pcm_rb_acquire_write(&loopbackRB, &framesToWrite, &pBuffer);
MA_COPY_MEMORY(pBuffer, pInput, framesToWrite);
ma_pcm_rb_commit_write(&loopbackRB, framesToWrite);
}
void data_callback_loopback_playback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uint32 frameCount)
{
ma_uint32 framesToRead;
void* pBuffer;
(void)pDevice;
(void)pInput;
/* Read from the ring buffer. */
framesToRead = frameCount;
ma_pcm_rb_acquire_read(&loopbackRB, &framesToRead, &pBuffer);
MA_COPY_MEMORY(pOutput, pBuffer, framesToRead);
ma_pcm_rb_commit_read(&loopbackRB, framesToRead);
}
static void do_loopback()
{
ma_result result;
ma_device_config deviceConfig;
ma_device_backend_config backend;
backend = ma_device_backend_config_init(DEVICE_BACKEND, NULL);
deviceConfig = ma_device_config_init(ma_device_type_loopback);
deviceConfig.threadingMode = threadingMode;
deviceConfig.capture.format = DEVICE_FORMAT;
deviceConfig.capture.channels = 2;
deviceConfig.sampleRate = DEVICE_SAMPLE_RATE;
deviceConfig.dataCallback = data_callback_loopback_capture;
deviceConfig.pBackendConfigs = &backend;
deviceConfig.backendConfigCount = 1;
result = ma_device_init_ex(&backend, 1, NULL, &deviceConfig, &device);
if (result != MA_SUCCESS) {
printf("Failed to initialize loopback device.\n");
return;
}
deviceConfig = ma_device_config_init(ma_device_type_playback);
deviceConfig.threadingMode = threadingMode;
deviceConfig.playback.format = DEVICE_FORMAT;
deviceConfig.playback.channels = 2;
deviceConfig.sampleRate = DEVICE_SAMPLE_RATE;
deviceConfig.dataCallback = data_callback_loopback_playback;
deviceConfig.pBackendConfigs = &backend;
deviceConfig.backendConfigCount = 1;
result = ma_device_init_ex(&backend, 1, NULL, &deviceConfig, &loopbackPlaybackDevice);
if (result != MA_SUCCESS) {
printf("Failed to initialize loopback playback device.\n");
return;
}
/* We need a ring buffer. */
printf("device.capture.internalPeriodSizeInFrames = %u\n", device.capture.internalPeriodSizeInFrames);
ma_pcm_rb_init(DEVICE_FORMAT, device.capture.channels, device.capture.internalPeriodSizeInFrames * 100, NULL, NULL, &loopbackRB);
if (ma_device_start(&loopbackPlaybackDevice) != MA_SUCCESS) {
printf("Failed to start loopback playback device.");
return;
}
if (ma_device_start(&device) != MA_SUCCESS) {
printf("Failed to start device.");
return;
}
}
static EM_BOOL on_canvas_click(int eventType, const EmscriptenMouseEvent* pMouseEvent, void* pUserData)
{
if (isRunning == MA_FALSE) {
if (pMouseEvent->button == 0) { /* Left click. */
/* */ if (pMouseEvent->button == 0) { /* Left click. */
do_playback();
} else if (pMouseEvent->button == 2) { /* Right click. */
} else if (pMouseEvent->button == 2) { /* Right click. */
do_duplex();
} else if (pMouseEvent->button == 1) { /* Middle click. */
do_loopback();
}
isRunning = MA_TRUE;
@@ -208,6 +295,7 @@ int main(int argc, char** argv)
printf("Click inside canvas to start playing:\n");
printf(" Left click for playback\n");
printf(" Right click for duplex\n");
printf(" Middle click for loopback\n");
/* The device must be started in response to an input event. */
emscripten_set_mouseup_callback("canvas", &device, 0, on_canvas_click);