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SDL_audio.h File Reference
#include "SDL_stdinc.h"
#include "SDL_error.h"
#include "SDL_endian.h"
#include "SDL_mutex.h"
#include "SDL_thread.h"
#include "SDL_rwops.h"
#include "begin_code.h"
#include "close_code.h"

Go to the source code of this file.


struct  SDL_AudioCVT
struct  SDL_AudioSpec


#define SDL_LoadWAV(file, spec, audio_buf, audio_len)   SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
#define SDL_MIX_MAXVOLUME   128
Audio flags
#define SDL_AUDIO_MASK_DATATYPE   (1<<8)
#define SDL_AUDIO_MASK_ENDIAN   (1<<12)
#define SDL_AUDIO_MASK_SIGNED   (1<<15)
Audio format flags

Defaults to LSB byte order.

#define AUDIO_U8   0x0008
#define AUDIO_S8   0x8008
#define AUDIO_U16LSB   0x0010
#define AUDIO_S16LSB   0x8010
#define AUDIO_U16MSB   0x1010
#define AUDIO_S16MSB   0x9010
#define AUDIO_U16   AUDIO_U16LSB
#define AUDIO_S16   AUDIO_S16LSB
int32 support
#define AUDIO_S32LSB   0x8020
#define AUDIO_S32MSB   0x9020
#define AUDIO_S32   AUDIO_S32LSB
float32 support
#define AUDIO_F32LSB   0x8120
#define AUDIO_F32MSB   0x9120
#define AUDIO_F32   AUDIO_F32LSB
Native audio byte ordering
Allow change flags

Which audio format changes are allowed when opening a device.

#define SDL_AUDIO_ALLOW_FORMAT_CHANGE   0x00000002


typedef SDL_AudioFormat format
typedef Uint8 int len
typedef struct SDL_AudioCVT SDL_AudioCVT
typedef Uint32 SDL_AudioDeviceID
typedef Uint16 SDL_AudioFormat
 Audio format flags. More...
typedef struct SDL_AudioSpec SDL_AudioSpec
typedef Uint8stream


DECLSPEC int SDLCALL SDL_BuildAudioCVT (SDL_AudioCVT *cvt, SDL_AudioFormat src_format, Uint8 src_channels, int src_rate, SDL_AudioFormat dst_format, Uint8 dst_channels, int dst_rate)
DECLSPEC void SDLCALL SDL_CloseAudio (void)
DECLSPEC void SDLCALL SDL_CloseAudioDevice (SDL_AudioDeviceID dev)
DECLSPEC int SDLCALL SDL_ConvertAudio (SDL_AudioCVT *cvt)
DECLSPEC void SDLCALL SDL_FreeWAV (Uint8 *audio_buf)
DECLSPEC const char *SDLCALL SDL_GetAudioDeviceName (int index, int iscapture)
DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver (void)
DECLSPEC int SDLCALL SDL_GetNumAudioDevices (int iscapture)
DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW (SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len)
DECLSPEC void SDLCALL SDL_MixAudio (Uint8 *dst, const Uint8 *src, Uint32 len, int volume)
DECLSPEC void SDLCALL SDL_MixAudioFormat (Uint8 *dst, const Uint8 *src, SDL_AudioFormat format, Uint32 len, int volume)
DECLSPEC int SDLCALL SDL_OpenAudio (SDL_AudioSpec *desired, SDL_AudioSpec *obtained)
DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice (const char *device, int iscapture, const SDL_AudioSpec *desired, SDL_AudioSpec *obtained, int allowed_changes)
typedef void (SDLCALL *SDL_AudioCallback)(void *userdata
Driver discovery functions

These functions return the list of built in audio drivers, in the order that they are normally initialized by default.

DECLSPEC int SDLCALL SDL_GetNumAudioDrivers (void)
DECLSPEC const char *SDLCALL SDL_GetAudioDriver (int index)
Initialization and cleanup
DECLSPEC int SDLCALL SDL_AudioInit (const char *driver_name)
DECLSPEC void SDLCALL SDL_AudioQuit (void)
Pause audio functions

These functions pause and unpause the audio callback processing. They should be called with a parameter of 0 after opening the audio device to start playing sound. This is so you can safely initialize data for your callback function after opening the audio device. Silence will be written to the audio device during the pause.

DECLSPEC void SDLCALL SDL_PauseAudio (int pause_on)
DECLSPEC void SDLCALL SDL_PauseAudioDevice (SDL_AudioDeviceID dev, int pause_on)
Audio lock functions

The lock manipulated by these functions protects the callback function. During a SDL_LockAudio()/SDL_UnlockAudio() pair, you can be guaranteed that the callback function is not running. Do not call these from the callback function or you will cause deadlock.

DECLSPEC void SDLCALL SDL_LockAudio (void)
DECLSPEC void SDLCALL SDL_LockAudioDevice (SDL_AudioDeviceID dev)
DECLSPEC void SDLCALL SDL_UnlockAudio (void)
DECLSPEC void SDLCALL SDL_UnlockAudioDevice (SDL_AudioDeviceID dev)

Audio state

Get the current audio state.

DECLSPEC SDL_AudioStatus SDLCALL SDL_GetAudioStatus (void)
DECLSPEC SDL_AudioStatus SDLCALL SDL_GetAudioDeviceStatus (SDL_AudioDeviceID dev)

Detailed Description

Access to the raw audio mixing buffer for the SDL library.

Definition in file SDL_audio.h.

Macro Definition Documentation

#define AUDIO_F32   AUDIO_F32LSB

Definition at line 114 of file SDL_audio.h.

Referenced by SDL_ConvertMono(), SDL_ConvertSurround(), and SDL_LoadWAV_RW().


Definition at line 125 of file SDL_audio.h.


Definition at line 123 of file SDL_audio.h.

#define AUDIO_S32   AUDIO_S32LSB

Definition at line 124 of file SDL_audio.h.

#define AUDIO_U16   AUDIO_U16LSB

Definition at line 122 of file SDL_audio.h.

Definition at line 143 of file SDL_audio.h.

Referenced by SDL_OpenAudio().


Definition at line 142 of file SDL_audio.h.

Referenced by open_audio_device().

#define SDL_AUDIO_ALLOW_FORMAT_CHANGE   0x00000002

Definition at line 141 of file SDL_audio.h.

Referenced by open_audio_device().


Definition at line 140 of file SDL_audio.h.

Referenced by open_audio_device().


Definition at line 76 of file SDL_audio.h.

Referenced by COREAUDIO_OpenDevice().

#define SDL_AUDIO_ISINT (   x)    (!SDL_AUDIO_ISFLOAT(x))

Definition at line 79 of file SDL_audio.h.


Definition at line 80 of file SDL_audio.h.


Definition at line 78 of file SDL_audio.h.

Referenced by COREAUDIO_OpenDevice(), and SDL_BuildAudioCVT().


Definition at line 81 of file SDL_audio.h.


Definition at line 71 of file SDL_audio.h.

Referenced by SDL_ConvertMono(), SDL_ConvertSurround(), and SDL_ConvertSurround_4().

#define SDL_AUDIO_MASK_DATATYPE   (1<<8)

Definition at line 72 of file SDL_audio.h.

#define SDL_AUDIO_MASK_ENDIAN   (1<<12)

Definition at line 73 of file SDL_audio.h.

#define SDL_AUDIO_MASK_SIGNED   (1<<15)

Definition at line 74 of file SDL_audio.h.

Referenced by SDL_ConvertMono(), SDL_ConvertSurround(), and SDL_ConvertSurround_4().


A structure to hold a set of audio conversion filters and buffers.

Definition at line 194 of file SDL_audio.h.

#define SDL_LoadWAV (   file,
)    SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)

Loads a WAV from a file. Compatibility convenience function.

Definition at line 419 of file SDL_audio.h.

#define SDL_MIX_MAXVOLUME   128

Definition at line 456 of file SDL_audio.h.

Referenced by SDL_MixAudioFormat().

Typedef Documentation

Definition at line 181 of file SDL_audio.h.

typedef Uint8 int len

Definition at line 159 of file SDL_audio.h.

typedef struct SDL_AudioCVT SDL_AudioCVT

SDL Audio Device IDs.

A successful call to SDL_OpenAudio() is always device id 1, and legacy SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls always returns devices >= 2 on success. The legacy calls are good both for backwards compatibility and when you don't care about multiple, specific, or capture devices.

Definition at line 298 of file SDL_audio.h.

Audio format flags.

These are what the 16 bits in SDL_AudioFormat currently mean... (Unspecified bits are always zero).

++-----------------------sample is signed if set
||       ++-----------sample is bigendian if set
||       ||
||       ||          ++---sample is float if set
||       ||          ||
||       ||          || +---sample bit size---+
||       ||          || |                     |
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00

There are macros in SDL 2.0 and later to query these bits.

Definition at line 64 of file SDL_audio.h.

typedef struct SDL_AudioSpec SDL_AudioSpec

The calculated values in this structure are calculated by SDL_OpenAudio().

typedef Uint8* stream

Definition at line 159 of file SDL_audio.h.

Enumeration Type Documentation


Definition at line 363 of file SDL_audio.h.

Function Documentation

SDL_AudioFormat  src_format,
Uint8  src_channels,
int  src_rate,
SDL_AudioFormat  dst_format,
Uint8  dst_channels,
int  dst_rate 

This function takes a source format and rate and a destination format and rate, and initializes the cvt structure with information needed by SDL_ConvertAudio() to convert a buffer of audio data from one format to the other.

-1 if the format conversion is not supported, 0 if there's no conversion needed, or 1 if the audio filter is set up.

Definition at line 958 of file SDL_audiocvt.c.

References SDL_AudioCVT::buf, SDL_AudioCVT::dst_format, SDL_AudioCVT::filter_index, SDL_AudioCVT::filters, SDL_AudioCVT::len, SDL_AudioCVT::len_mult, SDL_AudioCVT::len_ratio, SDL_AudioCVT::needed, NULL, SDL_AudioCVT::rate_incr, SDL_AUDIO_BITSIZE, SDL_AUDIO_ISSIGNED, SDL_BuildAudioResampleCVT(), SDL_BuildAudioTypeCVT(), SDL_ConvertMono(), SDL_ConvertStereo(), SDL_ConvertStrip(), SDL_ConvertStrip_2(), SDL_ConvertSurround(), SDL_ConvertSurround_4(), SDL_InvalidParamError, SDL_SetError(), SDL_zerop, and SDL_AudioCVT::src_format.

Referenced by open_audio_device().

DECLSPEC void SDLCALL SDL_CloseAudio ( void  )

This function shuts down audio processing and closes the audio device.

Definition at line 1169 of file SDL_audio.c.

References SDL_CloseAudioDevice().

DECLSPEC void SDLCALL SDL_CloseAudioDevice ( SDL_AudioDeviceID  dev)

Definition at line 1159 of file SDL_audio.c.

References close_audio_device(), get_audio_device(), and NULL.

Referenced by open_audio_device(), SDL_AudioQuit(), and SDL_CloseAudio().

DECLSPEC int SDLCALL SDL_ConvertAudio ( SDL_AudioCVT cvt)

Once you have initialized the cvt structure using SDL_BuildAudioCVT(), created an audio buffer cvt->buf, and filled it with cvt->len bytes of audio data in the source format, this function will convert it in-place to the desired format.

The data conversion may expand the size of the audio data, so the buffer cvt->buf should be allocated after the cvt structure is initialized by SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.

Definition at line 774 of file SDL_audiocvt.c.

References SDL_AudioCVT::buf, SDL_AudioCVT::filter_index, SDL_AudioCVT::filters, SDL_AudioCVT::len, SDL_AudioCVT::len_cvt, NULL, SDL_SetError(), and SDL_AudioCVT::src_format.

Referenced by SDL_RunAudio().

DECLSPEC void SDLCALL SDL_FreeWAV ( Uint8 audio_buf)

This function frees data previously allocated with SDL_LoadWAV_RW()

Definition at line 601 of file SDL_wave.c.

References SDL_free().

DECLSPEC const char* SDLCALL SDL_GetAudioDeviceName ( int  index,
int  iscapture 

Get the human-readable name of a specific audio device. Must be a value between 0 and (number of audio devices-1). Only valid after a successfully initializing the audio subsystem. The values returned by this function reflect the latest call to SDL_GetNumAudioDevices(); recall that function to redetect available hardware.

The string returned by this function is UTF-8 encoded, read-only, and managed internally. You are not to free it. If you need to keep the string for any length of time, you should make your own copy of it, as it will be invalid next time any of several other SDL functions is called.

Definition at line 708 of file SDL_audio.c.

References DEFAULT_INPUT_DEVNAME, DEFAULT_OUTPUT_DEVNAME, SDL_AudioDriverImpl::HasCaptureSupport, SDL_AudioDriver::impl, SDL_AudioDriver::inputDeviceCount, SDL_AudioDriver::inputDevices, NULL, SDL_AudioDriverImpl::OnlyHasDefaultInputDevice, SDL_AudioDriverImpl::OnlyHasDefaultOutputDevice, SDL_AudioDriver::outputDeviceCount, SDL_AudioDriver::outputDevices, SDL_INIT_AUDIO, SDL_SetError(), and SDL_WasInit().

DECLSPEC const char* SDLCALL SDL_GetAudioDriver ( int  index)

Definition at line 553 of file SDL_audio.c.

References NULL, and SDL_GetNumAudioDrivers().

Referenced by SDLTest_CommonInit().

DECLSPEC SDL_AudioStatus SDLCALL SDL_GetAudioStatus ( void  )

Definition at line 1103 of file SDL_audio.c.

References SDL_GetAudioDeviceStatus().

DECLSPEC const char* SDLCALL SDL_GetCurrentAudioDriver ( void  )

This function returns the name of the current audio driver, or NULL if no driver has been initialized.

Definition at line 618 of file SDL_audio.c.

References SDL_AudioDriver::name.

Referenced by SDLTest_CommonInit().

DECLSPEC int SDLCALL SDL_GetNumAudioDevices ( int  iscapture)

Get the number of available devices exposed by the current driver. Only valid after a successfully initializing the audio subsystem. Returns -1 if an explicit list of devices can't be determined; this is not an error. For example, if SDL is set up to talk to a remote audio server, it can't list every one available on the Internet, but it will still allow a specific host to be specified to SDL_OpenAudioDevice().

In many common cases, when this function returns a value <= 0, it can still successfully open the default device (NULL for first argument of SDL_OpenAudioDevice()).

Definition at line 671 of file SDL_audio.c.

References SDL_AudioDriverImpl::DetectDevices, free_device_list(), SDL_AudioDriverImpl::HasCaptureSupport, SDL_AudioDriver::impl, SDL_AudioDriver::inputDeviceCount, SDL_AudioDriver::inputDevices, SDL_AudioDriverImpl::OnlyHasDefaultInputDevice, SDL_AudioDriverImpl::OnlyHasDefaultOutputDevice, SDL_AudioDriver::outputDeviceCount, SDL_AudioDriver::outputDevices, SDL_AddCaptureAudioDevice(), SDL_AddOutputAudioDevice(), SDL_INIT_AUDIO, and SDL_WasInit().

Referenced by open_audio_device().

DECLSPEC int SDLCALL SDL_GetNumAudioDrivers ( void  )

Definition at line 547 of file SDL_audio.c.

References SDL_arraysize.

Referenced by SDL_GetAudioDriver(), and SDLTest_CommonInit().

int  freesrc,
SDL_AudioSpec spec,
Uint8 **  audio_buf,
Uint32 audio_len 

This function loads a WAVE from the data source, automatically freeing that source if freesrc is non-zero. For example, to load a WAVE file, you could do:

* SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);

If this function succeeds, it returns the given SDL_AudioSpec, filled with the audio data format of the wave data, and sets *audio_buf to a malloc()'d buffer containing the audio data, and sets *audio_len to the length of that audio buffer, in bytes. You need to free the audio buffer with SDL_FreeWAV() when you are done with it.

This function returns NULL and sets the SDL error message if the wave file cannot be opened, uses an unknown data format, or is corrupt. Currently raw and MS-ADPCM WAVE files are supported.

Definition at line 405 of file SDL_wave.c.

References AUDIO_F32, AUDIO_S16, AUDIO_S32, AUDIO_U8, WaveFMT::bitspersample, WaveFMT::channels, SDL_AudioSpec::channels, chunk, DATA, Chunk::data, WaveFMT::encoding, FACT, FMT, SDL_AudioSpec::format, SDL_AudioSpec::freq, WaveFMT::frequency, IEEE_FLOAT_CODE, if(), IMA_ADPCM_CODE, IMA_ADPCM_decode(), InitIMA_ADPCM(), InitMS_ADPCM(), Chunk::length, LIST, Chunk::magic, MP3_CODE, MS_ADPCM_CODE, MS_ADPCM_decode(), NULL, PCM_CODE, ReadChunk(), RIFF, RW_SEEK_CUR, SDL_AudioSpec::samples, SDL_AUDIO_BITSIZE, SDL_free(), SDL_memset(), SDL_ReadLE32(), SDL_RWclose, SDL_RWseek, SDL_SetError(), SDL_SwapLE16, SDL_SwapLE32, SDL_zero, and WAVE.

DECLSPEC void SDLCALL SDL_LockAudio ( void  )

Definition at line 1137 of file SDL_audio.c.

References SDL_LockAudioDevice().

DECLSPEC void SDLCALL SDL_LockAudioDevice ( SDL_AudioDeviceID  dev)

Definition at line 1127 of file SDL_audio.c.

References get_audio_device(), SDL_AudioDriver::impl, and SDL_AudioDriverImpl::LockDevice.

Referenced by SDL_LockAudio().

DECLSPEC void SDLCALL SDL_MixAudio ( Uint8 dst,
const Uint8 src,
Uint32  len,
int  volume 

This takes two audio buffers of the playing audio format and mixes them, performing addition, volume adjustment, and overflow clipping. The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME for full audio volume. Note this does not change hardware volume. This is provided for convenience – you can mix your own audio data.

Definition at line 1268 of file SDL_audio.c.

References SDL_AudioDevice::convert, SDL_AudioSpec::format, get_audio_device(), SDL_AudioCVT::needed, NULL, SDL_MixAudioFormat(), SDL_AudioDevice::spec, and SDL_AudioCVT::src_format.

DECLSPEC void SDLCALL SDL_MixAudioFormat ( Uint8 dst,
const Uint8 src,
SDL_AudioFormat  format,
Uint32  len,
int  volume 

This works like SDL_MixAudio(), but you specify the audio format instead of using the format of audio device 1. Thus it can be used when no audio device is open at all.

Definition at line 90 of file SDL_mixer.c.


Referenced by SDL_MixAudio().

DECLSPEC int SDLCALL SDL_OpenAudio ( SDL_AudioSpec desired,
SDL_AudioSpec obtained 

This function opens the audio device with the desired parameters, and returns 0 if successful, placing the actual hardware parameters in the structure pointed to by obtained. If obtained is NULL, the audio data passed to the callback function will be guaranteed to be in the requested format, and will be automatically converted to the hardware audio format if necessary. This function returns -1 if it failed to open the audio device, or couldn't set up the audio thread.

When filling in the desired audio spec structure,

  • desired->freq should be the desired audio frequency in samples-per- second.
  • desired->format should be the desired audio format.
  • desired->samples is the desired size of the audio buffer, in samples. This number should be a power of two, and may be adjusted by the audio driver to a value more suitable for the hardware. Good values seem to range between 512 and 8096 inclusive, depending on the application and CPU speed. Smaller values yield faster response time, but can lead to underflow if the application is doing heavy processing and cannot fill the audio buffer in time. A stereo sample consists of both right and left channels in LR ordering. Note that the number of samples is directly related to time by the following formula:
    ms = (samples*1000)/freq
  • desired->size is the size in bytes of the audio buffer, and is calculated by SDL_OpenAudio().
  • desired->silence is the value used to set the buffer to silence, and is calculated by SDL_OpenAudio().
  • desired->callback should be set to a function that will be called when the audio device is ready for more data. It is passed a pointer to the audio buffer, and the length in bytes of the audio buffer. This function usually runs in a separate thread, and so you should protect data structures that it accesses by calling SDL_LockAudio() and SDL_UnlockAudio() in your code.
  • desired->userdata is passed as the first parameter to your callback function.

The audio device starts out playing silence when it's opened, and should be enabled for playing by calling SDL_PauseAudio(0) when you are ready for your audio callback function to be called. Since the audio driver may modify the requested size of the audio buffer, you should allocate any local mixing buffers after you open the audio device.

Definition at line 1049 of file SDL_audio.c.

References NULL, open_audio_device(), SDL_assert, SDL_AUDIO_ALLOW_ANY_CHANGE, SDL_INIT_AUDIO, SDL_InitSubSystem(), SDL_SetError(), and SDL_WasInit().

Referenced by SDLTest_CommonInit().

DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice ( const char *  device,
int  iscapture,
const SDL_AudioSpec desired,
SDL_AudioSpec obtained,
int  allowed_changes 

Open a specific audio device. Passing in a device name of NULL requests the most reasonable default (and is equivalent to calling SDL_OpenAudio()).

The device name is a UTF-8 string reported by SDL_GetAudioDeviceName(), but some drivers allow arbitrary and driver-specific strings, such as a hostname/IP address for a remote audio server, or a filename in the diskaudio driver.

0 on error, a valid device ID that is >= 2 on success.

SDL_OpenAudio(), unlike this function, always acts on device ID 1.

Definition at line 1078 of file SDL_audio.c.

References open_audio_device().

DECLSPEC void SDLCALL SDL_PauseAudio ( int  pause_on)

Definition at line 1120 of file SDL_audio.c.

References SDL_PauseAudioDevice().

DECLSPEC void SDLCALL SDL_UnlockAudio ( void  )

Definition at line 1153 of file SDL_audio.c.

References SDL_UnlockAudioDevice().

DECLSPEC void SDLCALL SDL_UnlockAudioDevice ( SDL_AudioDeviceID  dev)
typedef void ( SDLCALL SDL_AudioCallback)

This function is called when the audio device needs more data.

userdataAn application-specific parameter saved in the SDL_AudioSpec structure
streamA pointer to the audio data buffer.
lenThe length of that buffer in bytes.

Once the callback returns, the buffer will no longer be valid. Stereo samples are stored in a LRLRLR ordering.