include/SDL_audio.h
author Ryan C. Gordon <icculus@icculus.org>
Thu, 03 Aug 2006 19:34:05 +0000
changeset 1964 071b6598d48f
parent 1895 c121d94672cb
child 1967 01e29c3e9a29
permissions -rw-r--r--
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!
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2006 Sam Lantinga
     4 
     5     This library is free software; you can redistribute it and/or
     6     modify it under the terms of the GNU Lesser General Public
     7     License as published by the Free Software Foundation; either
     8     version 2.1 of the License, or (at your option) any later version.
     9 
    10     This library is distributed in the hope that it will be useful,
    11     but WITHOUT ANY WARRANTY; without even the implied warranty of
    12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    13     Lesser General Public License for more details.
    14 
    15     You should have received a copy of the GNU Lesser General Public
    16     License along with this library; if not, write to the Free Software
    17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
    18 
    19     Sam Lantinga
    20     slouken@libsdl.org
    21 */
    22 
    23 /**
    24  * \file SDL_audio.h
    25  *
    26  * Access to the raw audio mixing buffer for the SDL library
    27  */
    28 
    29 #ifndef _SDL_audio_h
    30 #define _SDL_audio_h
    31 
    32 #include "SDL_stdinc.h"
    33 #include "SDL_error.h"
    34 #include "SDL_endian.h"
    35 #include "SDL_mutex.h"
    36 #include "SDL_thread.h"
    37 #include "SDL_rwops.h"
    38 
    39 #include "begin_code.h"
    40 /* Set up for C function definitions, even when using C++ */
    41 #ifdef __cplusplus
    42 /* *INDENT-OFF* */
    43 extern "C" {
    44 /* *INDENT-ON* */
    45 #endif
    46 
    47 typedef Uint16 SDL_AudioFormat;
    48 
    49 /* The calculated values in this structure are calculated by SDL_OpenAudio() */
    50 typedef struct SDL_AudioSpec
    51 {
    52     int freq;                   /* DSP frequency -- samples per second */
    53     SDL_AudioFormat format;     /* Audio data format */
    54     Uint8 channels;             /* Number of channels: 1 mono, 2 stereo */
    55     Uint8 silence;              /* Audio buffer silence value (calculated) */
    56     Uint16 samples;             /* Audio buffer size in samples (power of 2) */
    57     Uint16 padding;             /* Necessary for some compile environments */
    58     Uint32 size;                /* Audio buffer size in bytes (calculated) */
    59     /* This function is called when the audio device needs more data.
    60        'stream' is a pointer to the audio data buffer
    61        'len' is the length of that buffer in bytes.
    62        Once the callback returns, the buffer will no longer be valid.
    63        Stereo samples are stored in a LRLRLR ordering.
    64      */
    65     void (SDLCALL * callback) (void *userdata, Uint8 * stream, int len);
    66     void *userdata;
    67 } SDL_AudioSpec;
    68 
    69 
    70 /*
    71  These are what the 16 bits in SDL_AudioFormat currently mean...
    72  (Unspecified bits are always zero.)
    73 
    74  ++-----------------------sample is signed if set
    75  ||
    76  ||       ++-----------sample is bigendian if set
    77  ||       ||
    78  ||       ||          ++---sample is float if set
    79  ||       ||          ||
    80  ||       ||          || +---sample bit size---+
    81  ||       ||          || |                     |
    82  15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
    83 
    84  There are macros in SDL 1.3 and later to query these bits.
    85 */
    86 
    87 #define SDL_AUDIO_MASK_BITSIZE       (0xFF)
    88 #define SDL_AUDIO_MASK_DATATYPE      (1<<8)
    89 #define SDL_AUDIO_MASK_ENDIAN        (1<<12)
    90 #define SDL_AUDIO_MASK_SIGNED        (1<<15)
    91 #define SDL_AUDIO_BITSIZE(x)         (x & SDL_AUDIO_MASK_BITSIZE)
    92 #define SDL_AUDIO_ISFLOAT(x)         (x & SDL_AUDIO_MASK_DATATYPE)
    93 #define SDL_AUDIO_ISBIGENDIAN(x)     (x & SDL_AUDIO_MASK_ENDIAN)
    94 #define SDL_AUDIO_ISSIGNED(x)        (x & SDL_AUDIO_MASK_SIGNED)
    95 #define SDL_AUDIO_ISINT(x)           (!SDL_AUDIO_ISFLOAT(x))
    96 #define SDL_AUDIO_ISLITTLEENDIAN(x)  (!SDL_AUDIO_ISBIGENDIAN(x))
    97 #define SDL_AUDIO_ISUNSIGNED(x)      (!SDL_AUDIO_ISSIGNED(x))
    98 
    99 /* Audio format flags (defaults to LSB byte order) */
   100 #define AUDIO_U8	0x0008  /* Unsigned 8-bit samples */
   101 #define AUDIO_S8	0x8008  /* Signed 8-bit samples */
   102 #define AUDIO_U16LSB	0x0010  /* Unsigned 16-bit samples */
   103 #define AUDIO_S16LSB	0x8010  /* Signed 16-bit samples */
   104 #define AUDIO_U16MSB	0x1010  /* As above, but big-endian byte order */
   105 #define AUDIO_S16MSB	0x9010  /* As above, but big-endian byte order */
   106 #define AUDIO_U16	AUDIO_U16LSB
   107 #define AUDIO_S16	AUDIO_S16LSB
   108 
   109 /* int32 support new to SDL 1.3 */
   110 #define AUDIO_S32LSB	0x8020  /* 32-bit integer samples */
   111 #define AUDIO_S32MSB	0x9020  /* As above, but big-endian byte order */
   112 #define AUDIO_S32	AUDIO_S32LSB
   113 #define AUDIO_U32LSB	0x0020  /* Unsigned 32-bit integer samples */
   114 #define AUDIO_U32MSB	0x1020  /* As above, but big-endian byte order */
   115 #define AUDIO_U32	AUDIO_U32LSB
   116 
   117 /* float32 support new to SDL 1.3 */
   118 #define AUDIO_F32LSB	0x8120  /* 32-bit floating point samples */
   119 #define AUDIO_F32MSB	0x9120  /* As above, but big-endian byte order */
   120 #define AUDIO_F32	AUDIO_F32LSB
   121 
   122 /* Native audio byte ordering */
   123 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
   124 #define AUDIO_U16SYS	AUDIO_U16LSB
   125 #define AUDIO_S16SYS	AUDIO_S16LSB
   126 #define AUDIO_S32SYS	AUDIO_S32LSB
   127 #define AUDIO_U32SYS	AUDIO_U32LSB
   128 #define AUDIO_F32SYS	AUDIO_F32LSB
   129 #else
   130 #define AUDIO_U16SYS	AUDIO_U16MSB
   131 #define AUDIO_S16SYS	AUDIO_S16MSB
   132 #define AUDIO_S32SYS	AUDIO_S32MSB
   133 #define AUDIO_U32SYS	AUDIO_U32MSB
   134 #define AUDIO_F32SYS	AUDIO_F32MSB
   135 #endif
   136 
   137 
   138 /* A structure to hold a set of audio conversion filters and buffers */
   139 typedef struct SDL_AudioCVT
   140 {
   141     int needed;                 /* Set to 1 if conversion possible */
   142     Uint16 src_format;          /* Source audio format */
   143     Uint16 dst_format;          /* Target audio format */
   144     double rate_incr;           /* Rate conversion increment */
   145     Uint8 *buf;                 /* Buffer to hold entire audio data */
   146     int len;                    /* Length of original audio buffer */
   147     int len_cvt;                /* Length of converted audio buffer */
   148     int len_mult;               /* buffer must be len*len_mult big */
   149     double len_ratio;           /* Given len, final size is len*len_ratio */
   150     void (SDLCALL * filters[10]) (struct SDL_AudioCVT * cvt, Uint16 format);
   151     int filter_index;           /* Current audio conversion function */
   152 } SDL_AudioCVT;
   153 
   154 
   155 /* Function prototypes */
   156 
   157 /* These functions return the list of built in video drivers, in the 
   158  * order that they are normally initialized by default.
   159  */
   160 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
   161 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
   162 
   163 /* These functions are used internally, and should not be used unless you
   164  * have a specific need to specify the audio driver you want to use.
   165  * You should normally use SDL_Init() or SDL_InitSubSystem().
   166  */
   167 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   168 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   169 
   170 /* This function returns the name of the current audio driver, or NULL
   171  * if no driver has been initialized.
   172  */
   173 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
   174 
   175 /*
   176  * This function opens the audio device with the desired parameters, and
   177  * returns 0 if successful, placing the actual hardware parameters in the
   178  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   179  * data passed to the callback function will be guaranteed to be in the
   180  * requested format, and will be automatically converted to the hardware
   181  * audio format if necessary.  This function returns -1 if it failed 
   182  * to open the audio device, or couldn't set up the audio thread.
   183  *
   184  * When filling in the desired audio spec structure,
   185  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   186  *  'desired->format' should be the desired audio format.
   187  *  'desired->samples' is the desired size of the audio buffer, in samples.
   188  *     This number should be a power of two, and may be adjusted by the audio
   189  *     driver to a value more suitable for the hardware.  Good values seem to
   190  *     range between 512 and 8096 inclusive, depending on the application and
   191  *     CPU speed.  Smaller values yield faster response time, but can lead
   192  *     to underflow if the application is doing heavy processing and cannot
   193  *     fill the audio buffer in time.  A stereo sample consists of both right
   194  *     and left channels in LR ordering.
   195  *     Note that the number of samples is directly related to time by the
   196  *     following formula:  ms = (samples*1000)/freq
   197  *  'desired->size' is the size in bytes of the audio buffer, and is
   198  *     calculated by SDL_OpenAudio().
   199  *  'desired->silence' is the value used to set the buffer to silence,
   200  *     and is calculated by SDL_OpenAudio().
   201  *  'desired->callback' should be set to a function that will be called
   202  *     when the audio device is ready for more data.  It is passed a pointer
   203  *     to the audio buffer, and the length in bytes of the audio buffer.
   204  *     This function usually runs in a separate thread, and so you should
   205  *     protect data structures that it accesses by calling SDL_LockAudio()
   206  *     and SDL_UnlockAudio() in your code.
   207  *  'desired->userdata' is passed as the first parameter to your callback
   208  *     function.
   209  *
   210  * The audio device starts out playing silence when it's opened, and should
   211  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   212  * for your audio callback function to be called.  Since the audio driver
   213  * may modify the requested size of the audio buffer, you should allocate
   214  * any local mixing buffers after you open the audio device.
   215  */
   216 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
   217                                           SDL_AudioSpec * obtained);
   218 
   219 /*
   220  * SDL Audio Device IDs.
   221  * A successful call to SDL_OpenAudio() is always device id 1, and legacy
   222  *  SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
   223  *  always returns devices >= 2 on success. The legacy calls are good both
   224  *  for backwards compatibility and when you don't care about multiple,
   225  *  specific, or capture devices.
   226  */
   227 typedef Uint32 SDL_AudioDeviceID;
   228 
   229 /*
   230  * Get the number of available devices exposed by the current driver.
   231  *  Only valid after a successfully initializing the audio subsystem.
   232  */
   233 extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
   234 
   235 /*
   236  * Get the human-readable name of a specific audio device.
   237  *  Must be a value between 0 and (number of audio devices-1).
   238  *  Only valid after a successfully initializing the audio subsystem.
   239  */
   240 extern DECLSPEC const char *SDLCALL SDL_GetAudioDevice(int index, int iscapture);
   241 
   242 
   243 /*
   244  * Open a specific audio device. Passing in a device name of NULL is
   245  *  equivalent to SDL_OpenAudio(). Returns 0 on error, a valid device ID
   246  *  on success.
   247  */
   248 extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(
   249                                                 const char * device,
   250                                                 int iscapture,
   251                                                 const SDL_AudioSpec * desired,
   252                                                 SDL_AudioSpec * obtained);
   253 
   254 
   255 
   256 /*
   257  * Get the current audio state:
   258  */
   259 typedef enum
   260 {
   261     SDL_AUDIO_STOPPED = 0,
   262     SDL_AUDIO_PLAYING,
   263     SDL_AUDIO_PAUSED
   264 } SDL_audiostatus;
   265 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   266 
   267 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioDeviceStatus(
   268                                                         SDL_AudioDeviceID dev);
   269 
   270 /*
   271  * This function pauses and unpauses the audio callback processing.
   272  * It should be called with a parameter of 0 after opening the audio
   273  * device to start playing sound.  This is so you can safely initialize
   274  * data for your callback function after opening the audio device.
   275  * Silence will be written to the audio device during the pause.
   276  */
   277 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   278 extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
   279                                                   int pause_on);
   280 
   281 /*
   282  * This function loads a WAVE from the data source, automatically freeing
   283  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   284  * you could do:
   285  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   286  *
   287  * If this function succeeds, it returns the given SDL_AudioSpec,
   288  * filled with the audio data format of the wave data, and sets
   289  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   290  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   291  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   292  * done with it.
   293  *
   294  * This function returns NULL and sets the SDL error message if the 
   295  * wave file cannot be opened, uses an unknown data format, or is 
   296  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   297  */
   298 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
   299                                                       int freesrc,
   300                                                       SDL_AudioSpec * spec,
   301                                                       Uint8 ** audio_buf,
   302                                                       Uint32 * audio_len);
   303 
   304 /* Compatibility convenience function -- loads a WAV from a file */
   305 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   306 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   307 
   308 /*
   309  * This function frees data previously allocated with SDL_LoadWAV_RW()
   310  */
   311 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
   312 
   313 /*
   314  * This function takes a source format and rate and a destination format
   315  * and rate, and initializes the 'cvt' structure with information needed
   316  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   317  * to the other.
   318  * Returns -1 if the format conversion is not supported, 0 if there's
   319  *  no conversion needed, or 1 if the audio filter is set up.
   320  */
   321 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
   322                                               Uint16 src_format,
   323                                               Uint8 src_channels,
   324                                               int src_rate,
   325                                               Uint16 dst_format,
   326                                               Uint8 dst_channels,
   327                                               int dst_rate);
   328 
   329 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   330  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   331  * audio data in the source format, this function will convert it in-place
   332  * to the desired format.
   333  * The data conversion may expand the size of the audio data, so the buffer
   334  * cvt->buf should be allocated after the cvt structure is initialized by
   335  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   336  */
   337 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
   338 
   339 /*
   340  * This takes two audio buffers of the playing audio format and mixes
   341  * them, performing addition, volume adjustment, and overflow clipping.
   342  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   343  * for full audio volume.  Note this does not change hardware volume.
   344  * This is provided for convenience -- you can mix your own audio data.
   345  */
   346 #define SDL_MIX_MAXVOLUME 128
   347 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
   348                                           Uint32 len, int volume);
   349 
   350 /*
   351  * This works like SDL_MixAudio, but you specify the audio format instead of
   352  *  using the format of audio device 1. Thus it can be used when no audio
   353  *  device is open at all.
   354  */
   355 extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst, const Uint8 * src,
   356                                                 SDL_AudioFormat format,
   357                                                 Uint32 len, int volume);
   358 
   359 /*
   360  * The lock manipulated by these functions protects the callback function.
   361  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   362  * callback function is not running.  Do not call these from the callback
   363  * function or you will cause deadlock.
   364  */
   365 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   366 extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
   367 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   368 extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
   369 
   370 /*
   371  * This function shuts down audio processing and closes the audio device.
   372  */
   373 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   374 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
   375 
   376 /*
   377  * Returns 1 if audio device is still functioning, zero if not, -1 on error.
   378  */
   379 extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
   380 
   381 
   382 /* Ends C function definitions when using C++ */
   383 #ifdef __cplusplus
   384 /* *INDENT-OFF* */
   385 }
   386 /* *INDENT-ON* */
   387 #endif
   388 #include "close_code.h"
   389 
   390 #endif /* _SDL_audio_h */
   391 
   392 /* vi: set ts=4 sw=4 expandtab: */