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1.3 API proposals for audio subsystem. Nothing in here is guaranteed to

 stay as-is! And none of it is implemented yet!

 Use at own risk!
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icculus committed Aug 3, 2006
1 parent 6313c55 commit b95660f5a891180ba7dab0a20b59609818f6107e

File 1 of 1 in b95660f

@@ -44,11 +44,13 @@ extern "C" {
/* *INDENT-ON* */
#endif

typedef Uint16 SDL_AudioFormat;

/* The calculated values in this structure are calculated by SDL_OpenAudio() */
typedef struct SDL_AudioSpec
{
int freq; /* DSP frequency -- samples per second */
Uint16 format; /* Audio data format */
SDL_AudioFormat format; /* Audio data format */
Uint8 channels; /* Number of channels: 1 mono, 2 stereo */
Uint8 silence; /* Audio buffer silence value (calculated) */
Uint16 samples; /* Audio buffer size in samples (power of 2) */
@@ -64,6 +66,36 @@ typedef struct SDL_AudioSpec
void *userdata;
} SDL_AudioSpec;


/*
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 1.3 and later to query these bits.
*/

#define SDL_AUDIO_MASK_BITSIZE (0xFF)
#define SDL_AUDIO_MASK_DATATYPE (1<<8)
#define SDL_AUDIO_MASK_ENDIAN (1<<12)
#define SDL_AUDIO_MASK_SIGNED (1<<15)
#define SDL_AUDIO_BITSIZE(x) (x & SDL_AUDIO_MASK_BITSIZE)
#define SDL_AUDIO_ISFLOAT(x) (x & SDL_AUDIO_MASK_DATATYPE)
#define SDL_AUDIO_ISBIGENDIAN(x) (x & SDL_AUDIO_MASK_ENDIAN)
#define SDL_AUDIO_ISSIGNED(x) (x & SDL_AUDIO_MASK_SIGNED)
#define SDL_AUDIO_ISINT(x) (!SDL_AUDIO_ISFLOAT(x))
#define SDL_AUDIO_ISLITTLEENDIAN(x) (!SDL_AUDIO_ISBIGENDIAN(x))
#define SDL_AUDIO_ISUNSIGNED(x) (!SDL_AUDIO_ISSIGNED(x))

/* Audio format flags (defaults to LSB byte order) */
#define AUDIO_U8 0x0008 /* Unsigned 8-bit samples */
#define AUDIO_S8 0x8008 /* Signed 8-bit samples */
@@ -74,13 +106,32 @@ typedef struct SDL_AudioSpec
#define AUDIO_U16 AUDIO_U16LSB
#define AUDIO_S16 AUDIO_S16LSB

/* int32 support new to SDL 1.3 */
#define AUDIO_S32LSB 0x8020 /* 32-bit integer samples */
#define AUDIO_S32MSB 0x9020 /* As above, but big-endian byte order */
#define AUDIO_S32 AUDIO_S32LSB
#define AUDIO_U32LSB 0x0020 /* Unsigned 32-bit integer samples */
#define AUDIO_U32MSB 0x1020 /* As above, but big-endian byte order */
#define AUDIO_U32 AUDIO_U32LSB

/* float32 support new to SDL 1.3 */
#define AUDIO_F32LSB 0x8120 /* 32-bit floating point samples */
#define AUDIO_F32MSB 0x9120 /* As above, but big-endian byte order */
#define AUDIO_F32 AUDIO_F32LSB

/* Native audio byte ordering */
#if SDL_BYTEORDER == SDL_LIL_ENDIAN
#define AUDIO_U16SYS AUDIO_U16LSB
#define AUDIO_S16SYS AUDIO_S16LSB
#define AUDIO_S32SYS AUDIO_S32LSB
#define AUDIO_U32SYS AUDIO_U32LSB
#define AUDIO_F32SYS AUDIO_F32LSB
#else
#define AUDIO_U16SYS AUDIO_U16MSB
#define AUDIO_S16SYS AUDIO_S16MSB
#define AUDIO_S32SYS AUDIO_S32MSB
#define AUDIO_U32SYS AUDIO_U32MSB
#define AUDIO_F32SYS AUDIO_F32MSB
#endif


@@ -165,6 +216,43 @@ extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
SDL_AudioSpec * obtained);

/*
* 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.
*/
typedef Uint32 SDL_AudioDeviceID;

/*
* Get the number of available devices exposed by the current driver.
* Only valid after a successfully initializing the audio subsystem.
*/
extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(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.
*/
extern DECLSPEC const char *SDLCALL SDL_GetAudioDevice(int index, int iscapture);


/*
* Open a specific audio device. Passing in a device name of NULL is
* equivalent to SDL_OpenAudio(). Returns 0 on error, a valid device ID
* on success.
*/
extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(
const char * device,
int iscapture,
const SDL_AudioSpec * desired,
SDL_AudioSpec * obtained);



/*
* Get the current audio state:
*/
@@ -176,6 +264,9 @@ typedef enum
} SDL_audiostatus;
extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);

extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioDeviceStatus(
SDL_AudioDeviceID dev);

/*
* This function pauses and unpauses the audio callback processing.
* It should be called with a parameter of 0 after opening the audio
@@ -184,6 +275,8 @@ extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
* Silence will be written to the audio device during the pause.
*/
extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
int pause_on);

/*
* This function loads a WAVE from the data source, automatically freeing
@@ -222,7 +315,8 @@ extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
* 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.
* This function returns 0, or -1 if there was an error.
* Returns -1 if the format conversion is not supported, 0 if there's
* no conversion needed, or 1 if the audio filter is set up.
*/
extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
Uint16 src_format,
@@ -253,19 +347,36 @@ extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
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.
*/
extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst, const Uint8 * src,
SDL_AudioFormat format,
Uint32 len, int volume);

/*
* The lock manipulated by these functions protects the callback function.
* During a LockAudio/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.
*/
extern DECLSPEC void SDLCALL SDL_LockAudio(void);
extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);

/*
* This function shuts down audio processing and closes the audio device.
*/
extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);

/*
* Returns 1 if audio device is still functioning, zero if not, -1 on error.
*/
extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);


/* Ends C function definitions when using C++ */

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