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miniaudio/extras/backends/sdl/backend_sdl.c
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David Reid 8890eac6aa One Big Beautiful Commit with refactoring to the device backend system. 
This includes API changes that affect custom backends.

`ma_backend_callbacks` has been renamed to `ma_device_backend_vtable`.
The reason for this change is to to be consistent with the naming
convention used in other parts of the library. In addition, using the
term "device backend" rather than just "backend" removes ambiguity with
decoding backends.

A change has been made to the way backends manage their internal state,
and some functions in the vtable have been updated to reflect this.
Previously internal state for stock backends were located directly in
the `ma_device` structure. This works fine if stock backends are the
only backends to be concerned about, but it falls apart when you need
to consider how to manage the internal state of custom backends since
they cannot modify the `ma_device` structure. In order to simplify and
unify state management between stock and custom backends, the decision
was made to change the backend system such that backends now manage
their own internal state.

When the context is initialized with `onContextInit`, the backend must
now allocate an internal state object and output a pointer to it via
an output parameter. Typically you would do something like this:

    ma_result custom_context_init(..., void** ppContextState)
    {
        ctx_state_t* state = malloc(...);

        ...

        *ppContextState = state;
        return MA_SUCCESS;
    }

miniaudio will store a pointer to the state object internally. When you
need to access this later in other backend callbacks, you can retrieve
it straight from the context with `ma_context_get_backend_state()`:

    state = (ctx_state_t*)ma_context_get_backend_state(pContext);

The same idea applies to devices and `onDeviceInit`. You can use
`ma_device_get_backend_state()` to get a pointer to the internal state
object.

When a context and device is initialized, backend-specific
configurations can be supplied. The way these configs are provided to
`onContextInit` and `onDeviceInit` has been changed. Previously, these
callbacks would take a `ma_context/device_config` object. These have
been replaced with a `const void*` which points to a backend-specific
config object which is defined by the backend. All stock backends have
their own backend-specific config object:

    struct ma_context_config_wasapi
    struct ma_context_config_pulseaudio
    etc.

    struct ma_device_config_wasapi
    struct ma_device_config_pulseaudio
    etc.

You can cast the config object inside the relevant callbacks:

    ma_result custom_context_init(..., const void* pBackendConfig, ...)
    {
        ctx_config_t* pCustomConfig = (ctx_config_t*)pBackendConfig;
    }

The backend itself defines whether or not a config is required. None of
the stock backends require a config. If the config is NULL, it'll use
defaults. It's recommended custom backends follow this convention.

In addition to the above, `onContextUninit` and `onDeviceUninit` have
been updated to return void instead of `ma_result`.

The last change to the backend vtable is a new callback called
`onBackendInfo`. This is used to fill the `ma_device_backend_info`
structure.

In addition to the backend vtable, some changes have been made to the
public API to make it much easier to support plugging in custom
backends.

Previously, plugging in more than one custom backend was a complete
mess. It was possible, but you had to use a stupid wrapper thing to
make it work, and you had no control over prioritization. The entire
thing was just aweful, so it's now been stripped out and replaced with
a brand new system.

When a context or device is initialized, it is done so with a config
which is standard across the entire library. A complication to this is
that backends can sometimes require their own backend-specific configs.
But since miniaudio cannot possibly know about custom backends, it
cannot put their config options inside `ma_context/device_config`. The
functions for initializing a context and device have been updated to
allow plugging in backend-specific configs.

When initializing a context, instead of passing in an array of
`ma_backend` enums, an array of `ma_device_backend_config` objects is
passed in instead. This object has two members: A pointer to a backend
vtable, and a pointer to a config object. It can be initialized
something like this:

    ma_context_config_custom customContextConfig;
    ... initialize the custom backend config if necessary ...

    ma_device_backend_config backends[] =
    {
        { ma_device_backend_custom,     &customContextConfig },
        { ma_device_backend_wasapi,     NULL },
        { ma_device_backend_pulseaudio, NULL }
    };

    ma_context_init(backends, backendCount, ...);

Here `ma_device_backend_custom` is our custom backend. You can see how
the config is mapped to the backend. For stock backends (WASAPI and
PulseAudio in this example), you can pass in NULL and just set the
relevant config options straight in `ma_context_config` exactly how it
was done before:

    ma_context_config contextConfig = ma_context_config_init();
    contextConfig.pulseaudio.pApplicationName = "My App";

Here we are just using the standard `ma_context_config` object for
configuring the stock PulseAudio backend. This is possible for all
stock backends, but for custom backends an explicit config object will
be required. You can still use a separate explicit config object for
stock backends if you prefer that style:

    ma_context_config_pulseaudio paContextConfig;
    paContextConfig = ma_context_config_pulseaudio_init();
    paContextConfig.pApplicationName = "My App";

    ma_device_backend_config backends[] =
    {
        { ma_device_backend_pulseaudio, &paContextConfig }
    };

Note that if you do not use custom backends, you can still pass in NULL
for the backends in which case defaults will be used like how it's
always worked in the past.

As with contexts, devices can also have their own backend-specific
configs associated with them. These work exactly the same way, except
these configs are passed into the main `ma_device_config` object. (A
future commit may make this consistent between contexts and devices).

    ma_device_backend_config deviceBackendConfigs[] =
    {
        { ma_device_backend_custom, &customDeviceConfig }
    };

    deviceConfig.pBackendConfigs    = deviceBackendConfigs;
    deviceConfig.backendConfigCount = backendCount;

    ma_device_init(&deviceConfig, &device);

This commit is just the start of many backend related changes. Future
commits will be cleaning up a lot of residual code from the old system,
such as removing `ma_backend`.
2025-07-14 18:05:55 +10:00

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/*
This implements a full-featured SDL2 backend. It's intentionally built using the same paradigms as the built-in backends in order to make
it suitable as a solid basis for a custom implementation. The SDL2 backend can be disabled with MA_NO_SDL, exactly like the built-in
backends. It supports both runtime and compile-time linking and respects the MA_NO_RUNTIME_LINKING option. It also works on Emscripten
which requires the `-s USE_SDL=2` option.
*/
#ifndef miniaudio_backend_sdl_c
#define miniaudio_backend_sdl_c
/* Include miniaudio.h if we're not including this file after the implementation. */
#if !defined(MINIAUDIO_IMPLEMENTATION) && !defined(MA_IMPLEMENTATION)
#include "../../../miniaudio.h"
#endif
#include "backend_sdl.h"
#include <string.h> /* memset() */
#include <assert.h>
#ifndef MA_SDL_ASSERT
#define MA_SDL_ASSERT(cond) assert(cond)
#endif
/* Support SDL on everything. */
#define MA_SUPPORT_SDL
/*
Only enable SDL if it's hasn't been explicitly disabled (MA_NO_SDL) or enabled (MA_ENABLE_SDL with
MA_ENABLE_ONLY_SPECIFIC_BACKENDS) and it's supported at compile time (MA_SUPPORT_SDL).
*/
#if defined(MA_SUPPORT_SDL) && !defined(MA_NO_SDL) && (!defined(MA_ENABLE_ONLY_SPECIFIC_BACKENDS) || defined(MA_ENABLE_SDL))
#define MA_HAS_SDL
#endif
/* SDL headers are necessary if using compile-time linking. Necessary for Emscripten. */
#if defined(MA_HAS_SDL)
#if defined(MA_NO_RUNTIME_LINKING) || defined(MA_EMSCRIPTEN)
#ifdef __has_include
#ifdef MA_EMSCRIPTEN
#if !__has_include(<SDL/SDL_audio.h>)
#undef MA_HAS_SDL
#endif
#else
#if !__has_include(<SDL2/SDL_audio.h>)
#undef MA_HAS_SDL
#endif
#endif
#endif
#endif
#endif
/* Don't compile in the SDL backend if it's been disabled. */
#if defined(MA_HAS_SDL)
#define MA_SDL_INIT_AUDIO 0x00000010
#define MA_AUDIO_U8 0x0008
#define MA_AUDIO_S16 0x8010
#define MA_AUDIO_S32 0x8020
#define MA_AUDIO_F32 0x8120
#define MA_SDL_AUDIO_ALLOW_FREQUENCY_CHANGE 0x00000001
#define MA_SDL_AUDIO_ALLOW_FORMAT_CHANGE 0x00000002
#define MA_SDL_AUDIO_ALLOW_CHANNELS_CHANGE 0x00000004
#define MA_SDL_AUDIO_ALLOW_ANY_CHANGE (MA_SDL_AUDIO_ALLOW_FREQUENCY_CHANGE | MA_SDL_AUDIO_ALLOW_FORMAT_CHANGE | MA_SDL_AUDIO_ALLOW_CHANNELS_CHANGE)
/* If we are linking at compile time we'll just #include SDL.h. Otherwise we can just redeclare some stuff to avoid the need for development packages to be installed. */
#ifdef MA_NO_RUNTIME_LINKING
#define SDL_MAIN_HANDLED
#ifdef MA_EMSCRIPTEN
#include <SDL/SDL.h>
#else
#include <SDL2/SDL.h>
#endif
typedef SDL_AudioCallback MA_SDL_AudioCallback;
typedef SDL_AudioSpec MA_SDL_AudioSpec;
typedef SDL_AudioFormat MA_SDL_AudioFormat;
typedef SDL_AudioDeviceID MA_SDL_AudioDeviceID;
#else
typedef void (* MA_SDL_AudioCallback)(void* userdata, ma_uint8* stream, int len);
typedef ma_uint16 MA_SDL_AudioFormat;
typedef ma_uint32 MA_SDL_AudioDeviceID;
typedef struct MA_SDL_AudioSpec
{
int freq;
MA_SDL_AudioFormat format;
ma_uint8 channels;
ma_uint8 silence;
ma_uint16 samples;
ma_uint16 padding;
ma_uint32 size;
MA_SDL_AudioCallback callback;
void* userdata;
} MA_SDL_AudioSpec;
#endif
typedef int (* MA_PFN_SDL_InitSubSystem)(ma_uint32 flags);
typedef void (* MA_PFN_SDL_QuitSubSystem)(ma_uint32 flags);
typedef int (* MA_PFN_SDL_GetNumAudioDevices)(int iscapture);
typedef const char* (* MA_PFN_SDL_GetAudioDeviceName)(int index, int iscapture);
typedef void (* MA_PFN_SDL_CloseAudioDevice)(MA_SDL_AudioDeviceID dev);
typedef MA_SDL_AudioDeviceID (* MA_PFN_SDL_OpenAudioDevice)(const char* device, int iscapture, const MA_SDL_AudioSpec* desired, MA_SDL_AudioSpec* obtained, int allowed_changes);
typedef void (* MA_PFN_SDL_PauseAudioDevice)(MA_SDL_AudioDeviceID dev, int pause_on);
typedef struct
{
ma_handle hSDL; /* A handle to the SDL2 shared object. We dynamically load function pointers at runtime so we can avoid linking. */
MA_PFN_SDL_InitSubSystem SDL_InitSubSystem;
MA_PFN_SDL_QuitSubSystem SDL_QuitSubSystem;
MA_PFN_SDL_GetNumAudioDevices SDL_GetNumAudioDevices;
MA_PFN_SDL_GetAudioDeviceName SDL_GetAudioDeviceName;
MA_PFN_SDL_CloseAudioDevice SDL_CloseAudioDevice;
MA_PFN_SDL_OpenAudioDevice SDL_OpenAudioDevice;
MA_PFN_SDL_PauseAudioDevice SDL_PauseAudioDevice;
} ma_context_state_sdl;
typedef struct
{
struct
{
int deviceID;
ma_format format;
ma_uint32 channels;
} capture;
struct
{
int deviceID;
ma_format format;
ma_uint32 channels;
} playback;
} ma_device_state_sdl;
MA_SDL_AudioFormat ma_format_to_sdl(ma_format format)
{
switch (format)
{
case ma_format_unknown: return 0;
case ma_format_u8: return MA_AUDIO_U8;
case ma_format_s16: return MA_AUDIO_S16;
case ma_format_s24: return MA_AUDIO_S32; /* Closest match. */
case ma_format_s32: return MA_AUDIO_S32;
case ma_format_f32: return MA_AUDIO_F32;
default: return 0;
}
}
ma_format ma_format_from_sdl(MA_SDL_AudioFormat format)
{
switch (format)
{
case MA_AUDIO_U8: return ma_format_u8;
case MA_AUDIO_S16: return ma_format_s16;
case MA_AUDIO_S32: return ma_format_s32;
case MA_AUDIO_F32: return ma_format_f32;
default: return ma_format_unknown;
}
}
static ma_context_state_sdl* ma_context_get_backend_state__sdl(ma_context* pContext)
{
return (ma_context_state_sdl*)ma_context_get_backend_state(pContext);
}
static ma_device_state_sdl* ma_device_get_backend_state__sdl(ma_device* pDevice)
{
return (ma_device_state_sdl*)ma_device_get_backend_state(pDevice);
}
static void ma_backend_info__sdl(ma_device_backend_info* pBackendInfo)
{
MA_SDL_ASSERT(pBackendInfo != NULL);
pBackendInfo->pName = "SDL2";
}
static ma_result ma_context_init__sdl(ma_context* pContext, const void* pContextBackendConfig, void** ppContextState)
{
ma_context_state_sdl* pContextStateSDL;
const ma_context_config_sdl* pContextConfigSDL = (ma_context_config_sdl*)pContextBackendConfig;
ma_log* pLog = ma_context_get_log(pContext);
int resultSDL;
/* The context config is not currently being used for this backend. */
(void)pContextConfigSDL;
/* Allocate our SDL-specific context data. */
pContextStateSDL = (ma_context_state_sdl*)ma_calloc(sizeof(*pContextStateSDL), ma_context_get_allocation_callbacks(pContext));
if (pContextStateSDL == NULL) {
return MA_OUT_OF_MEMORY;
}
#ifndef MA_NO_RUNTIME_LINKING
{
/* We'll use a list of possible shared object names for easier extensibility. */
size_t iName;
const char* pSDLNames[] = {
#if defined(_WIN32)
"SDL2.dll"
#elif defined(__APPLE__)
"SDL2.framework/SDL2"
#else
"libSDL2-2.0.so.0"
#endif
};
/* Check if we have SDL2 installed somewhere. If not it's not usable and we need to abort. */
for (iName = 0; iName < ma_countof(pSDLNames); iName += 1) {
pContextStateSDL->hSDL = ma_dlopen(pLog, pSDLNames[iName]);
if (pContextStateSDL->hSDL != NULL) {
break;
}
}
if (pContextStateSDL->hSDL == NULL) {
ma_free(pContextStateSDL, ma_context_get_allocation_callbacks(pContext));
return MA_NO_BACKEND; /* SDL2 could not be loaded. */
}
/* Now that we have the handle to the shared object we can go ahead and load some function pointers. */
pContextStateSDL->SDL_InitSubSystem = (MA_PFN_SDL_InitSubSystem )ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_InitSubSystem");
pContextStateSDL->SDL_QuitSubSystem = (MA_PFN_SDL_QuitSubSystem )ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_QuitSubSystem");
pContextStateSDL->SDL_GetNumAudioDevices = (MA_PFN_SDL_GetNumAudioDevices)ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_GetNumAudioDevices");
pContextStateSDL->SDL_GetAudioDeviceName = (MA_PFN_SDL_GetAudioDeviceName)ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_GetAudioDeviceName");
pContextStateSDL->SDL_CloseAudioDevice = (MA_PFN_SDL_CloseAudioDevice )ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_CloseAudioDevice");
pContextStateSDL->SDL_OpenAudioDevice = (MA_PFN_SDL_OpenAudioDevice )ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_OpenAudioDevice");
pContextStateSDL->SDL_PauseAudioDevice = (MA_PFN_SDL_PauseAudioDevice )ma_dlsym(pLog, pContextStateSDL->hSDL, "SDL_PauseAudioDevice");
}
#else
{
pContextStateSDL->SDL_InitSubSystem = SDL_InitSubSystem;
pContextStateSDL->SDL_QuitSubSystem = SDL_QuitSubSystem;
pContextStateSDL->SDL_GetNumAudioDevices = SDL_GetNumAudioDevices;
pContextStateSDL->SDL_GetAudioDeviceName = SDL_GetAudioDeviceName;
pContextStateSDL->SDL_CloseAudioDevice = SDL_CloseAudioDevice;
pContextStateSDL->SDL_OpenAudioDevice = SDL_OpenAudioDevice;
pContextStateSDL->SDL_PauseAudioDevice = SDL_PauseAudioDevice;
}
#endif /* MA_NO_RUNTIME_LINKING */
resultSDL = pContextStateSDL->SDL_InitSubSystem(MA_SDL_INIT_AUDIO);
if (resultSDL != 0) {
ma_dlclose(pLog, pContextStateSDL->hSDL);
ma_free(pContextStateSDL, ma_context_get_allocation_callbacks(pContext));
return MA_ERROR;
}
*ppContextState = pContextStateSDL;
return MA_SUCCESS;
}
static void ma_context_uninit__sdl(ma_context* pContext)
{
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(pContext);
MA_SDL_ASSERT(pContextStateSDL != NULL);
pContextStateSDL->SDL_QuitSubSystem(MA_SDL_INIT_AUDIO);
/* Close the handle to the SDL shared object last. */
ma_dlclose(ma_context_get_log(pContext), pContextStateSDL->hSDL);
pContextStateSDL->hSDL = NULL;
ma_free(pContextStateSDL, ma_context_get_allocation_callbacks(pContext));
}
static ma_result ma_context_enumerate_devices__sdl(ma_context* pContext, ma_enum_devices_callback_proc callback, void* pCallbackUserData)
{
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(pContext);
ma_bool32 isTerminated = MA_FALSE;
ma_bool32 cbResult;
int iDevice;
MA_SDL_ASSERT(pContextStateSDL != NULL);
/* Playback */
if (!isTerminated) {
int deviceCount = pContextStateSDL->SDL_GetNumAudioDevices(0);
for (iDevice = 0; iDevice < deviceCount; ++iDevice) {
ma_device_info deviceInfo;
memset(&deviceInfo, 0, sizeof(deviceInfo));
deviceInfo.id.custom.i = iDevice;
ma_strncpy_s(deviceInfo.name, sizeof(deviceInfo.name), pContextStateSDL->SDL_GetAudioDeviceName(iDevice, 0), (size_t)-1);
if (iDevice == 0) {
deviceInfo.isDefault = MA_TRUE;
}
cbResult = callback(ma_device_type_playback, &deviceInfo, pCallbackUserData);
if (cbResult == MA_FALSE) {
isTerminated = MA_TRUE;
break;
}
}
}
/* Capture */
if (!isTerminated) {
int deviceCount = pContextStateSDL->SDL_GetNumAudioDevices(1);
for (iDevice = 0; iDevice < deviceCount; ++iDevice) {
ma_device_info deviceInfo;
memset(&deviceInfo, 0, sizeof(deviceInfo));
deviceInfo.id.custom.i = iDevice;
ma_strncpy_s(deviceInfo.name, sizeof(deviceInfo.name), pContextStateSDL->SDL_GetAudioDeviceName(iDevice, 1), (size_t)-1);
if (iDevice == 0) {
deviceInfo.isDefault = MA_TRUE;
}
cbResult = callback(ma_device_type_capture, &deviceInfo, pCallbackUserData);
if (cbResult == MA_FALSE) {
isTerminated = MA_TRUE;
break;
}
}
}
return MA_SUCCESS;
}
static ma_result ma_context_get_device_info__sdl(ma_context* pContext, ma_device_type deviceType, const ma_device_id* pDeviceID, ma_device_info* pDeviceInfo)
{
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(pContext);
#if !defined(__EMSCRIPTEN__)
MA_SDL_AudioSpec desiredSpec;
MA_SDL_AudioSpec obtainedSpec;
MA_SDL_AudioDeviceID tempDeviceID;
const char* pDeviceName;
#endif
if (pDeviceID == NULL) {
if (deviceType == ma_device_type_playback) {
pDeviceInfo->id.custom.i = 0;
ma_strncpy_s(pDeviceInfo->name, sizeof(pDeviceInfo->name), "Default Playback Device", (size_t)-1);
} else {
pDeviceInfo->id.custom.i = 0;
ma_strncpy_s(pDeviceInfo->name, sizeof(pDeviceInfo->name), "Default Capture Device", (size_t)-1);
}
} else {
pDeviceInfo->id.custom.i = pDeviceID->custom.i;
ma_strncpy_s(pDeviceInfo->name, sizeof(pDeviceInfo->name), pContextStateSDL->SDL_GetAudioDeviceName(pDeviceID->custom.i, (deviceType == ma_device_type_playback) ? 0 : 1), (size_t)-1);
}
if (pDeviceInfo->id.custom.i == 0) {
pDeviceInfo->isDefault = MA_TRUE;
}
/*
To get an accurate idea on the backend's native format we need to open the device. Not ideal, but it's the only way. An
alternative to this is to report all channel counts, sample rates and formats, but that doesn't offer a good representation
of the device's _actual_ ideal format.
Note: With Emscripten, it looks like non-zero values need to be specified for desiredSpec. Whatever is specified in
desiredSpec will be used by SDL since it uses it just does it's own format conversion internally. Therefore, from what
I can tell, there's no real way to know the device's actual format which means I'm just going to fall back to the full
range of channels and sample rates on Emscripten builds.
*/
#if defined(__EMSCRIPTEN__)
/* Good practice to prioritize the best format first so that the application can use the first data format as their chosen one if desired. */
pDeviceInfo->nativeDataFormatCount = 3;
pDeviceInfo->nativeDataFormats[0].format = ma_format_s16;
pDeviceInfo->nativeDataFormats[0].channels = 0; /* All channel counts supported. */
pDeviceInfo->nativeDataFormats[0].sampleRate = 0; /* All sample rates supported. */
pDeviceInfo->nativeDataFormats[0].flags = 0;
pDeviceInfo->nativeDataFormats[1].format = ma_format_s32;
pDeviceInfo->nativeDataFormats[1].channels = 0; /* All channel counts supported. */
pDeviceInfo->nativeDataFormats[1].sampleRate = 0; /* All sample rates supported. */
pDeviceInfo->nativeDataFormats[1].flags = 0;
pDeviceInfo->nativeDataFormats[2].format = ma_format_u8;
pDeviceInfo->nativeDataFormats[2].channels = 0; /* All channel counts supported. */
pDeviceInfo->nativeDataFormats[2].sampleRate = 0; /* All sample rates supported. */
pDeviceInfo->nativeDataFormats[2].flags = 0;
#else
memset(&desiredSpec, 0, sizeof(desiredSpec));
pDeviceName = NULL;
if (pDeviceID != NULL) {
pDeviceName = pContextStateSDL->SDL_GetAudioDeviceName(pDeviceID->custom.i, (deviceType == ma_device_type_playback) ? 0 : 1);
}
tempDeviceID = pContextStateSDL->SDL_OpenAudioDevice(pDeviceName, (deviceType == ma_device_type_playback) ? 0 : 1, &desiredSpec, &obtainedSpec, MA_SDL_AUDIO_ALLOW_ANY_CHANGE);
if (tempDeviceID == 0) {
ma_log_postf(ma_context_get_log(pContext), MA_LOG_LEVEL_ERROR, "Failed to open SDL device.");
return MA_FAILED_TO_OPEN_BACKEND_DEVICE;
}
pContextStateSDL->SDL_CloseAudioDevice(tempDeviceID);
/* Only reporting a single native data format. It'll be whatever SDL decides is the best. */
pDeviceInfo->nativeDataFormatCount = 1;
pDeviceInfo->nativeDataFormats[0].format = ma_format_from_sdl(obtainedSpec.format);
pDeviceInfo->nativeDataFormats[0].channels = obtainedSpec.channels;
pDeviceInfo->nativeDataFormats[0].sampleRate = obtainedSpec.freq;
pDeviceInfo->nativeDataFormats[0].flags = 0;
/* If miniaudio does not support the format, just use f32 as the native format (SDL will do the necessary conversions for us). */
if (pDeviceInfo->nativeDataFormats[0].format == ma_format_unknown) {
pDeviceInfo->nativeDataFormats[0].format = ma_format_f32;
}
#endif /* __EMSCRIPTEN__ */
return MA_SUCCESS;
}
void ma_audio_callback_capture__sdl(void* pUserData, ma_uint8* pBuffer, int bufferSizeInBytes)
{
ma_device* pDevice = (ma_device*)pUserData;
ma_device_state_sdl* pDeviceStateSDL = ma_device_get_backend_state__sdl(pDevice);
ma_device_handle_backend_data_callback(pDevice, NULL, pBuffer, (ma_uint32)bufferSizeInBytes / ma_get_bytes_per_frame(pDeviceStateSDL->capture.format, pDeviceStateSDL->capture.channels));
}
void ma_audio_callback_playback__sdl(void* pUserData, ma_uint8* pBuffer, int bufferSizeInBytes)
{
ma_device* pDevice = (ma_device*)pUserData;
ma_device_state_sdl* pDeviceStateSDL = ma_device_get_backend_state__sdl(pDevice);
ma_device_handle_backend_data_callback(pDevice, pBuffer, NULL, (ma_uint32)bufferSizeInBytes / ma_get_bytes_per_frame(pDeviceStateSDL->playback.format, pDeviceStateSDL->playback.channels));
}
static ma_result ma_device_init_internal__sdl(ma_device* pDevice, ma_context_state_sdl* pContextStateSDL, ma_device_state_sdl* pDeviceStateSDL, const ma_device_config_sdl* pDeviceConfigSDL, ma_device_type deviceType, ma_device_descriptor* pDescriptor)
{
MA_SDL_AudioSpec desiredSpec;
MA_SDL_AudioSpec obtainedSpec;
const char* pDeviceName;
int deviceID;
(void)pDeviceConfigSDL;
/*
SDL is a little bit awkward with specifying the buffer size, You need to specify the size of the buffer in frames, but since we may
have requested a period size in milliseconds we'll need to convert, which depends on the sample rate. But there's a possibility that
the sample rate just set to 0, which indicates that the native sample rate should be used. There's no practical way to calculate this
that I can think of right now so I'm just using MA_DEFAULT_SAMPLE_RATE.
*/
if (pDescriptor->sampleRate == 0) {
pDescriptor->sampleRate = MA_DEFAULT_SAMPLE_RATE;
}
/*
When determining the period size, you need to take defaults into account. This is how the size of the period should be determined.
1) If periodSizeInFrames is not 0, use periodSizeInFrames; else
2) If periodSizeInMilliseconds is not 0, use periodSizeInMilliseconds; else
3) If both periodSizeInFrames and periodSizeInMilliseconds is 0, use the backend's default. If the backend does not allow a default
buffer size, use a default value of MA_DEFAULT_PERIOD_SIZE_IN_MILLISECONDS_LOW_LATENCY or
MA_DEFAULT_PERIOD_SIZE_IN_MILLISECONDS_CONSERVATIVE depending on the value of pConfig->performanceProfile.
Note that options 2 and 3 require knowledge of the sample rate in order to convert it to a frame count. You should try to keep the
calculation of the period size as accurate as possible, but sometimes it's just not practical so just use whatever you can.
A helper function called ma_calculate_buffer_size_in_frames_from_descriptor() is available to do all of this for you which is what
we'll be using here.
*/
pDescriptor->periodSizeInFrames = ma_calculate_buffer_size_in_frames_from_descriptor(pDescriptor, pDescriptor->sampleRate, ma_performance_profile_low_latency);
/* SDL wants the buffer size to be a power of 2 for some reason. */
if (pDescriptor->periodSizeInFrames > 32768) {
pDescriptor->periodSizeInFrames = 32768;
} else {
pDescriptor->periodSizeInFrames = ma_next_power_of_2(pDescriptor->periodSizeInFrames);
}
/* We now have enough information to set up the device. */
memset(&desiredSpec, 0, sizeof(desiredSpec));
desiredSpec.freq = (int)pDescriptor->sampleRate;
desiredSpec.format = ma_format_to_sdl(pDescriptor->format);
desiredSpec.channels = (ma_uint8)pDescriptor->channels;
desiredSpec.samples = (ma_uint16)pDescriptor->periodSizeInFrames;
desiredSpec.callback = (deviceType == ma_device_type_capture) ? ma_audio_callback_capture__sdl : ma_audio_callback_playback__sdl;
desiredSpec.userdata = pDeviceStateSDL;
/* We'll fall back to f32 if we don't have an appropriate mapping between SDL and miniaudio. */
if (desiredSpec.format == 0) {
desiredSpec.format = MA_AUDIO_F32;
}
pDeviceName = NULL;
if (pDescriptor->pDeviceID != NULL) {
pDeviceName = pContextStateSDL->SDL_GetAudioDeviceName(pDescriptor->pDeviceID->custom.i, (deviceType == ma_device_type_playback) ? 0 : 1);
}
deviceID = pContextStateSDL->SDL_OpenAudioDevice(pDeviceName, (deviceType == ma_device_type_playback) ? 0 : 1, &desiredSpec, &obtainedSpec, MA_SDL_AUDIO_ALLOW_ANY_CHANGE);
if (deviceID == 0) {
ma_log_postf(ma_device_get_log(pDevice), MA_LOG_LEVEL_ERROR, "Failed to open SDL2 device.");
return MA_FAILED_TO_OPEN_BACKEND_DEVICE;
}
/* The descriptor needs to be updated with our actual settings. */
pDescriptor->format = ma_format_from_sdl(obtainedSpec.format);
pDescriptor->channels = obtainedSpec.channels;
pDescriptor->sampleRate = (ma_uint32)obtainedSpec.freq;
ma_channel_map_init_standard(ma_standard_channel_map_default, pDescriptor->channelMap, ma_countof(pDescriptor->channelMap), pDescriptor->channels);
pDescriptor->periodSizeInFrames = obtainedSpec.samples;
pDescriptor->periodCount = 1; /* SDL doesn't use the notion of period counts, so just set to 1. */
if (deviceType == ma_device_type_playback) {
pDeviceStateSDL->playback.deviceID = deviceID;
pDeviceStateSDL->playback.format = pDescriptor->format;
pDeviceStateSDL->playback.channels = pDescriptor->channels;
} else {
pDeviceStateSDL->capture.deviceID = deviceID;
pDeviceStateSDL->capture.format = pDescriptor->format;
pDeviceStateSDL->capture.channels = pDescriptor->channels;
}
return MA_SUCCESS;
}
static ma_result ma_device_init__sdl(ma_device* pDevice, const void* pDeviceBackendConfig, ma_device_descriptor* pDescriptorPlayback, ma_device_descriptor* pDescriptorCapture, void** ppDeviceState)
{
ma_device_state_sdl* pDeviceStateSDL;
ma_device_config_sdl* pDeviceConfigSDL = (ma_device_config_sdl*)pDeviceBackendConfig;
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(ma_device_get_context(pDevice));
ma_device_type deviceType = ma_device_get_type(pDevice);
ma_result result;
/* SDL does not support loopback mode, so must return MA_DEVICE_TYPE_NOT_SUPPORTED if it's requested. */
if (deviceType == ma_device_type_loopback) {
return MA_DEVICE_TYPE_NOT_SUPPORTED;
}
/* We need to allocate our backend-specific data. */
pDeviceStateSDL = (ma_device_state_sdl*)ma_calloc(sizeof(*pDeviceStateSDL), ma_device_get_allocation_callbacks(pDevice));
if (pDeviceStateSDL == NULL) {
return MA_OUT_OF_MEMORY;
}
if (deviceType == ma_device_type_capture || deviceType == ma_device_type_duplex) {
result = ma_device_init_internal__sdl(pDevice, pContextStateSDL, pDeviceStateSDL, pDeviceConfigSDL, ma_device_type_capture, pDescriptorCapture);
if (result != MA_SUCCESS) {
ma_free(pDeviceStateSDL, ma_device_get_allocation_callbacks(pDevice));
return result;
}
}
if (deviceType == ma_device_type_playback || deviceType == ma_device_type_duplex) {
result = ma_device_init_internal__sdl(pDevice, pContextStateSDL, pDeviceStateSDL, pDeviceConfigSDL, ma_device_type_playback, pDescriptorPlayback);
if (result != MA_SUCCESS) {
if (deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_CloseAudioDevice(pDeviceStateSDL->capture.deviceID);
}
ma_free(pDeviceStateSDL, ma_device_get_allocation_callbacks(pDevice));
return result;
}
}
*ppDeviceState = pDeviceStateSDL;
return MA_SUCCESS;
}
static void ma_device_uninit__sdl(ma_device* pDevice)
{
ma_device_state_sdl* pDeviceStateSDL = ma_device_get_backend_state__sdl(pDevice);
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(ma_device_get_context(pDevice));
ma_device_type deviceType = ma_device_get_type(pDevice);
if (deviceType == ma_device_type_capture || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_CloseAudioDevice(pDeviceStateSDL->capture.deviceID);
}
if (deviceType == ma_device_type_playback || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_CloseAudioDevice(pDeviceStateSDL->playback.deviceID);
}
ma_free(pDeviceStateSDL, ma_device_get_allocation_callbacks(pDevice));
}
static ma_result ma_device_start__sdl(ma_device* pDevice)
{
ma_device_state_sdl* pDeviceStateSDL = ma_device_get_backend_state__sdl(pDevice);
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(ma_device_get_context(pDevice));
ma_device_type deviceType = ma_device_get_type(pDevice);
if (deviceType == ma_device_type_capture || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_PauseAudioDevice(pDeviceStateSDL->capture.deviceID, 0);
}
if (deviceType == ma_device_type_playback || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_PauseAudioDevice(pDeviceStateSDL->playback.deviceID, 0);
}
return MA_SUCCESS;
}
static ma_result ma_device_stop__sdl(ma_device* pDevice)
{
ma_device_state_sdl* pDeviceStateSDL = ma_device_get_backend_state__sdl(pDevice);
ma_context_state_sdl* pContextStateSDL = ma_context_get_backend_state__sdl(ma_device_get_context(pDevice));
ma_device_type deviceType = ma_device_get_type(pDevice);
if (deviceType == ma_device_type_capture || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_PauseAudioDevice(pDeviceStateSDL->capture.deviceID, 1);
}
if (deviceType == ma_device_type_playback || deviceType == ma_device_type_duplex) {
pContextStateSDL->SDL_PauseAudioDevice(pDeviceStateSDL->playback.deviceID, 1);
}
return MA_SUCCESS;
}
static ma_device_backend_vtable ma_gDeviceBackendVTable_SDL =
{
ma_backend_info__sdl,
ma_context_init__sdl,
ma_context_uninit__sdl,
ma_context_enumerate_devices__sdl,
ma_context_get_device_info__sdl,
ma_device_init__sdl,
ma_device_uninit__sdl,
ma_device_start__sdl,
ma_device_stop__sdl,
NULL, /* onDeviceRead */
NULL, /* onDeviceWrite */
NULL, /* onDeviceLoop */
NULL /* onDeviceWakeup */
};
ma_device_backend_vtable* ma_device_backend_sdl = &ma_gDeviceBackendVTable_SDL;
#else
ma_device_backend_vtable* ma_device_backend_sdl = NULL;
#endif /* MA_HAS_SDL */
MA_API ma_context_config_sdl ma_context_config_sdl_init(void)
{
ma_context_config_sdl config;
memset(&config, 0, sizeof(config));
return config;
}
MA_API ma_device_config_sdl ma_device_config_sdl_init(void)
{
ma_device_config_sdl config;
memset(&config, 0, sizeof(config));
return config;
}
#endif /* miniaudio_backend_sdl_c */
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