include/SDL_audio.h
author Ryan C. Gordon <icculus@icculus.org>
Tue, 03 Oct 2006 20:48:42 +0000
branchSDL-ryan-multiple-audio-device
changeset 3791 be33495e4d97
parent 3790 8f8209f8da6d
child 3792 866c310e2cb5
permissions -rw-r--r--
Updated 1.3 audio documentation.
     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 
   114 /* float32 support new to SDL 1.3 */
   115 #define AUDIO_F32LSB	0x8120  /* 32-bit floating point samples */
   116 #define AUDIO_F32MSB	0x9120  /* As above, but big-endian byte order */
   117 #define AUDIO_F32	AUDIO_F32LSB
   118 
   119 /* Native audio byte ordering */
   120 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
   121 #define AUDIO_U16SYS	AUDIO_U16LSB
   122 #define AUDIO_S16SYS	AUDIO_S16LSB
   123 #define AUDIO_S32SYS	AUDIO_S32LSB
   124 #define AUDIO_F32SYS	AUDIO_F32LSB
   125 #else
   126 #define AUDIO_U16SYS	AUDIO_U16MSB
   127 #define AUDIO_S16SYS	AUDIO_S16MSB
   128 #define AUDIO_S32SYS	AUDIO_S32MSB
   129 #define AUDIO_F32SYS	AUDIO_F32MSB
   130 #endif
   131 
   132 
   133 /* A structure to hold a set of audio conversion filters and buffers */
   134 struct SDL_AudioCVT;
   135 typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
   136                                           SDL_AudioFormat format);
   137 
   138 typedef struct SDL_AudioCVT
   139 {
   140     int needed;                 /* Set to 1 if conversion possible */
   141     SDL_AudioFormat src_format; /* Source audio format */
   142     SDL_AudioFormat dst_format; /* Target audio format */
   143     double rate_incr;           /* Rate conversion increment */
   144     Uint8 *buf;                 /* Buffer to hold entire audio data */
   145     int len;                    /* Length of original audio buffer */
   146     int len_cvt;                /* Length of converted audio buffer */
   147     int len_mult;               /* buffer must be len*len_mult big */
   148     double len_ratio;           /* Given len, final size is len*len_ratio */
   149     SDL_AudioFilter filters[10];        /* Filter list */
   150     int filter_index;           /* Current audio conversion function */
   151 } SDL_AudioCVT;
   152 
   153 
   154 /* Function prototypes */
   155 
   156 /* These functions return the list of built in video drivers, in the 
   157  * order that they are normally initialized by default.
   158  */
   159 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
   160 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
   161 
   162 /* These functions are used internally, and should not be used unless you
   163  * have a specific need to specify the audio driver you want to use.
   164  * You should normally use SDL_Init() or SDL_InitSubSystem().
   165  */
   166 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   167 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   168 
   169 /* This function returns the name of the current audio driver, or NULL
   170  * if no driver has been initialized.
   171  */
   172 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
   173 
   174 /*
   175  * This function opens the audio device with the desired parameters, and
   176  * returns 0 if successful, placing the actual hardware parameters in the
   177  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   178  * data passed to the callback function will be guaranteed to be in the
   179  * requested format, and will be automatically converted to the hardware
   180  * audio format if necessary.  This function returns -1 if it failed 
   181  * to open the audio device, or couldn't set up the audio thread.
   182  *
   183  * When filling in the desired audio spec structure,
   184  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   185  *  'desired->format' should be the desired audio format.
   186  *  'desired->samples' is the desired size of the audio buffer, in samples.
   187  *     This number should be a power of two, and may be adjusted by the audio
   188  *     driver to a value more suitable for the hardware.  Good values seem to
   189  *     range between 512 and 8096 inclusive, depending on the application and
   190  *     CPU speed.  Smaller values yield faster response time, but can lead
   191  *     to underflow if the application is doing heavy processing and cannot
   192  *     fill the audio buffer in time.  A stereo sample consists of both right
   193  *     and left channels in LR ordering.
   194  *     Note that the number of samples is directly related to time by the
   195  *     following formula:  ms = (samples*1000)/freq
   196  *  'desired->size' is the size in bytes of the audio buffer, and is
   197  *     calculated by SDL_OpenAudio().
   198  *  'desired->silence' is the value used to set the buffer to silence,
   199  *     and is calculated by SDL_OpenAudio().
   200  *  'desired->callback' should be set to a function that will be called
   201  *     when the audio device is ready for more data.  It is passed a pointer
   202  *     to the audio buffer, and the length in bytes of the audio buffer.
   203  *     This function usually runs in a separate thread, and so you should
   204  *     protect data structures that it accesses by calling SDL_LockAudio()
   205  *     and SDL_UnlockAudio() in your code.
   206  *  'desired->userdata' is passed as the first parameter to your callback
   207  *     function.
   208  *
   209  * The audio device starts out playing silence when it's opened, and should
   210  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   211  * for your audio callback function to be called.  Since the audio driver
   212  * may modify the requested size of the audio buffer, you should allocate
   213  * any local mixing buffers after you open the audio device.
   214  */
   215 extern DECLSPEC int SDLCALL SDL_OpenAudio(const SDL_AudioSpec * desired,
   216                                           SDL_AudioSpec * obtained);
   217 
   218 /*
   219  * SDL Audio Device IDs.
   220  * A successful call to SDL_OpenAudio() is always device id 1, and legacy
   221  *  SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
   222  *  always returns devices >= 2 on success. The legacy calls are good both
   223  *  for backwards compatibility and when you don't care about multiple,
   224  *  specific, or capture devices.
   225  */
   226 typedef Uint32 SDL_AudioDeviceID;
   227 
   228 /*
   229  * Get the number of available devices exposed by the current driver.
   230  *  Only valid after a successfully initializing the audio subsystem.
   231  *  Returns -1 if an explicit list of devices can't be determined; this is
   232  *  not an error. For example, if SDL is set up to talk to a remote audio
   233  *  server, it can't list every one available on the Internet, but it will
   234  *  still allow a specific host to be specified to SDL_OpenAudioDevice().
   235  * In many common cases, when this function returns a value <= 0, it can still
   236  *  successfully open the default device (NULL for first argument of
   237  *  SDL_OpenAudioDevice()).
   238  */
   239 extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
   240 
   241 /*
   242  * Get the human-readable name of a specific audio device.
   243  *  Must be a value between 0 and (number of audio devices-1).
   244  *  Only valid after a successfully initializing the audio subsystem.
   245  *  The values returned by this function reflect the latest call to
   246  *  SDL_GetNumAudioDevices(); recall that function to redetect available
   247  *  hardware.
   248  *
   249  * The string returned by this function is UTF-8 encoded, read-only, and
   250  *  managed internally. You are not to free it. If you need to keep the
   251  *  string for any length of time, you should make your own copy of it, as it
   252  *  will be invalid next time any of several other SDL functions is called.
   253  */
   254 extern DECLSPEC const char *SDLCALL SDL_GetAudioDevice(int index,
   255                                                        int iscapture);
   256 
   257 
   258 /*
   259  * Open a specific audio device. Passing in a device name of NULL requests
   260  *  the most reasonable default (and is equivalent to calling SDL_OpenAudio()).
   261  * The device name is a UTF-8 string reported by SDL_GetAudioDevice(), but
   262  *  some drivers allow arbitrary and driver-specific strings, such as a
   263  *  hostname/IP address for a remote audio server, or a filename in the
   264  *  diskaudio driver.
   265  * Returns 0 on error, a valid device ID that is >= 2 on success.
   266  *  SDL_OpenAudio(), unlike this function, always acts on device ID 1.
   267  */
   268 extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
   269                                                               *device,
   270                                                               int iscapture,
   271                                                               const
   272                                                               SDL_AudioSpec *
   273                                                               desired,
   274                                                               SDL_AudioSpec *
   275                                                               obtained);
   276 
   277 
   278 
   279 /*
   280  * Get the current audio state:
   281  */
   282 typedef enum
   283 {
   284     SDL_AUDIO_STOPPED = 0,
   285     SDL_AUDIO_PLAYING,
   286     SDL_AUDIO_PAUSED
   287 } SDL_audiostatus;
   288 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   289 
   290 extern DECLSPEC SDL_audiostatus SDLCALL
   291 SDL_GetAudioDeviceStatus(SDL_AudioDeviceID dev);
   292 
   293 /*
   294  * This function pauses and unpauses the audio callback processing.
   295  * It should be called with a parameter of 0 after opening the audio
   296  * device to start playing sound.  This is so you can safely initialize
   297  * data for your callback function after opening the audio device.
   298  * Silence will be written to the audio device during the pause.
   299  */
   300 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   301 extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
   302                                                   int pause_on);
   303 
   304 /*
   305  * This function loads a WAVE from the data source, automatically freeing
   306  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   307  * you could do:
   308  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   309  *
   310  * If this function succeeds, it returns the given SDL_AudioSpec,
   311  * filled with the audio data format of the wave data, and sets
   312  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   313  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   314  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   315  * done with it.
   316  *
   317  * This function returns NULL and sets the SDL error message if the 
   318  * wave file cannot be opened, uses an unknown data format, or is 
   319  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   320  */
   321 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
   322                                                       int freesrc,
   323                                                       SDL_AudioSpec * spec,
   324                                                       Uint8 ** audio_buf,
   325                                                       Uint32 * audio_len);
   326 
   327 /* Compatibility convenience function -- loads a WAV from a file */
   328 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   329 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   330 
   331 /*
   332  * This function frees data previously allocated with SDL_LoadWAV_RW()
   333  */
   334 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
   335 
   336 /*
   337  * This function takes a source format and rate and a destination format
   338  * and rate, and initializes the 'cvt' structure with information needed
   339  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   340  * to the other.
   341  * Returns -1 if the format conversion is not supported, 0 if there's
   342  *  no conversion needed, or 1 if the audio filter is set up.
   343  */
   344 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
   345                                               SDL_AudioFormat src_format,
   346                                               Uint8 src_channels,
   347                                               int src_rate,
   348                                               SDL_AudioFormat dst_format,
   349                                               Uint8 dst_channels,
   350                                               int dst_rate);
   351 
   352 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   353  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   354  * audio data in the source format, this function will convert it in-place
   355  * to the desired format.
   356  * The data conversion may expand the size of the audio data, so the buffer
   357  * cvt->buf should be allocated after the cvt structure is initialized by
   358  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   359  */
   360 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
   361 
   362 /*
   363  * This takes two audio buffers of the playing audio format and mixes
   364  * them, performing addition, volume adjustment, and overflow clipping.
   365  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   366  * for full audio volume.  Note this does not change hardware volume.
   367  * This is provided for convenience -- you can mix your own audio data.
   368  */
   369 #define SDL_MIX_MAXVOLUME 128
   370 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
   371                                           Uint32 len, int volume);
   372 
   373 /*
   374  * This works like SDL_MixAudio, but you specify the audio format instead of
   375  *  using the format of audio device 1. Thus it can be used when no audio
   376  *  device is open at all.
   377  */
   378 extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
   379                                                 const Uint8 * src,
   380                                                 SDL_AudioFormat format,
   381                                                 Uint32 len, int volume);
   382 
   383 /*
   384  * The lock manipulated by these functions protects the callback function.
   385  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   386  * callback function is not running.  Do not call these from the callback
   387  * function or you will cause deadlock.
   388  */
   389 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   390 extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
   391 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   392 extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
   393 
   394 /*
   395  * This function shuts down audio processing and closes the audio device.
   396  */
   397 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   398 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
   399 
   400 /*
   401  * Returns 1 if audio device is still functioning, zero if not, -1 on error.
   402  */
   403 extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
   404 
   405 
   406 /* Ends C function definitions when using C++ */
   407 #ifdef __cplusplus
   408 /* *INDENT-OFF* */
   409 }
   410 /* *INDENT-ON* */
   411 #endif
   412 #include "close_code.h"
   413 
   414 #endif /* _SDL_audio_h */
   415 
   416 /* vi: set ts=4 sw=4 expandtab: */