include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Sun, 07 Jun 2009 02:45:55 +0000
changeset 3169 f294338ca6eb
parent 3021 f3dcf04412cf
child 3407 d3baf5ac4e37
permissions -rw-r--r--
indent
     1 /*
     2     SDL - Simple DirectMedia Layer
     3     Copyright (C) 1997-2009 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 /* Which audio format changes are allowed when opening a device */
   133 #define SDL_AUDIO_ALLOW_FREQUENCY_CHANGE    0x00000001
   134 #define SDL_AUDIO_ALLOW_FORMAT_CHANGE       0x00000002
   135 #define SDL_AUDIO_ALLOW_CHANNELS_CHANGE     0x00000004
   136 #define SDL_AUDIO_ALLOW_ANY_CHANGE          (SDL_AUDIO_ALLOW_FREQUENCY_CHANGE|SDL_AUDIO_ALLOW_FORMAT_CHANGE|SDL_AUDIO_ALLOW_CHANNELS_CHANGE)
   137 
   138 /* A structure to hold a set of audio conversion filters and buffers */
   139 struct SDL_AudioCVT;
   140 typedef void (SDLCALL * SDL_AudioFilter) (struct SDL_AudioCVT * cvt,
   141                                           SDL_AudioFormat format);
   142 
   143 typedef struct SDL_AudioCVT
   144 {
   145     int needed;                 /* Set to 1 if conversion possible */
   146     SDL_AudioFormat src_format; /* Source audio format */
   147     SDL_AudioFormat dst_format; /* Target audio format */
   148     double rate_incr;           /* Rate conversion increment */
   149     Uint8 *buf;                 /* Buffer to hold entire audio data */
   150     int len;                    /* Length of original audio buffer */
   151     int len_cvt;                /* Length of converted audio buffer */
   152     int len_mult;               /* buffer must be len*len_mult big */
   153     double len_ratio;           /* Given len, final size is len*len_ratio */
   154     SDL_AudioFilter filters[10];        /* Filter list */
   155     int filter_index;           /* Current audio conversion function */
   156 } SDL_AudioCVT;
   157 
   158 
   159 /* Function prototypes */
   160 
   161 /* These functions return the list of built in audio drivers, in the
   162  * order that they are normally initialized by default.
   163  */
   164 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
   165 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
   166 
   167 /* These functions are used internally, and should not be used unless you
   168  * have a specific need to specify the audio driver you want to use.
   169  * You should normally use SDL_Init() or SDL_InitSubSystem().
   170  */
   171 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   172 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   173 
   174 /* This function returns the name of the current audio driver, or NULL
   175  * if no driver has been initialized.
   176  */
   177 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
   178 
   179 /*
   180  * This function opens the audio device with the desired parameters, and
   181  * returns 0 if successful, placing the actual hardware parameters in the
   182  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   183  * data passed to the callback function will be guaranteed to be in the
   184  * requested format, and will be automatically converted to the hardware
   185  * audio format if necessary.  This function returns -1 if it failed 
   186  * to open the audio device, or couldn't set up the audio thread.
   187  *
   188  * When filling in the desired audio spec structure,
   189  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   190  *  'desired->format' should be the desired audio format.
   191  *  'desired->samples' is the desired size of the audio buffer, in samples.
   192  *     This number should be a power of two, and may be adjusted by the audio
   193  *     driver to a value more suitable for the hardware.  Good values seem to
   194  *     range between 512 and 8096 inclusive, depending on the application and
   195  *     CPU speed.  Smaller values yield faster response time, but can lead
   196  *     to underflow if the application is doing heavy processing and cannot
   197  *     fill the audio buffer in time.  A stereo sample consists of both right
   198  *     and left channels in LR ordering.
   199  *     Note that the number of samples is directly related to time by the
   200  *     following formula:  ms = (samples*1000)/freq
   201  *  'desired->size' is the size in bytes of the audio buffer, and is
   202  *     calculated by SDL_OpenAudio().
   203  *  'desired->silence' is the value used to set the buffer to silence,
   204  *     and is calculated by SDL_OpenAudio().
   205  *  'desired->callback' should be set to a function that will be called
   206  *     when the audio device is ready for more data.  It is passed a pointer
   207  *     to the audio buffer, and the length in bytes of the audio buffer.
   208  *     This function usually runs in a separate thread, and so you should
   209  *     protect data structures that it accesses by calling SDL_LockAudio()
   210  *     and SDL_UnlockAudio() in your code.
   211  *  'desired->userdata' is passed as the first parameter to your callback
   212  *     function.
   213  *
   214  * The audio device starts out playing silence when it's opened, and should
   215  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   216  * for your audio callback function to be called.  Since the audio driver
   217  * may modify the requested size of the audio buffer, you should allocate
   218  * any local mixing buffers after you open the audio device.
   219  */
   220 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
   221                                           SDL_AudioSpec * obtained);
   222 
   223 /*
   224  * SDL Audio Device IDs.
   225  * A successful call to SDL_OpenAudio() is always device id 1, and legacy
   226  *  SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
   227  *  always returns devices >= 2 on success. The legacy calls are good both
   228  *  for backwards compatibility and when you don't care about multiple,
   229  *  specific, or capture devices.
   230  */
   231 typedef Uint32 SDL_AudioDeviceID;
   232 
   233 /*
   234  * Get the number of available devices exposed by the current driver.
   235  *  Only valid after a successfully initializing the audio subsystem.
   236  *  Returns -1 if an explicit list of devices can't be determined; this is
   237  *  not an error. For example, if SDL is set up to talk to a remote audio
   238  *  server, it can't list every one available on the Internet, but it will
   239  *  still allow a specific host to be specified to SDL_OpenAudioDevice().
   240  * In many common cases, when this function returns a value <= 0, it can still
   241  *  successfully open the default device (NULL for first argument of
   242  *  SDL_OpenAudioDevice()).
   243  */
   244 extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
   245 
   246 /*
   247  * Get the human-readable name of a specific audio device.
   248  *  Must be a value between 0 and (number of audio devices-1).
   249  *  Only valid after a successfully initializing the audio subsystem.
   250  *  The values returned by this function reflect the latest call to
   251  *  SDL_GetNumAudioDevices(); recall that function to redetect available
   252  *  hardware.
   253  *
   254  * The string returned by this function is UTF-8 encoded, read-only, and
   255  *  managed internally. You are not to free it. If you need to keep the
   256  *  string for any length of time, you should make your own copy of it, as it
   257  *  will be invalid next time any of several other SDL functions is called.
   258  */
   259 extern DECLSPEC const char *SDLCALL SDL_GetAudioDeviceName(int index,
   260                                                            int iscapture);
   261 
   262 
   263 /*
   264  * Open a specific audio device. Passing in a device name of NULL requests
   265  *  the most reasonable default (and is equivalent to calling SDL_OpenAudio()).
   266  * The device name is a UTF-8 string reported by SDL_GetAudioDevice(), but
   267  *  some drivers allow arbitrary and driver-specific strings, such as a
   268  *  hostname/IP address for a remote audio server, or a filename in the
   269  *  diskaudio driver.
   270  * Returns 0 on error, a valid device ID that is >= 2 on success.
   271  *  SDL_OpenAudio(), unlike this function, always acts on device ID 1.
   272  */
   273 extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
   274                                                               *device,
   275                                                               int iscapture,
   276                                                               const
   277                                                               SDL_AudioSpec *
   278                                                               desired,
   279                                                               SDL_AudioSpec *
   280                                                               obtained,
   281                                                               int
   282                                                               allowed_changes);
   283 
   284 
   285 
   286 /*
   287  * Get the current audio state:
   288  */
   289 typedef enum
   290 {
   291     SDL_AUDIO_STOPPED = 0,
   292     SDL_AUDIO_PLAYING,
   293     SDL_AUDIO_PAUSED
   294 } SDL_audiostatus;
   295 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   296 
   297 extern DECLSPEC SDL_audiostatus SDLCALL
   298 SDL_GetAudioDeviceStatus(SDL_AudioDeviceID dev);
   299 
   300 /*
   301  * This function pauses and unpauses the audio callback processing.
   302  * It should be called with a parameter of 0 after opening the audio
   303  * device to start playing sound.  This is so you can safely initialize
   304  * data for your callback function after opening the audio device.
   305  * Silence will be written to the audio device during the pause.
   306  */
   307 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   308 extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
   309                                                   int pause_on);
   310 
   311 /*
   312  * This function loads a WAVE from the data source, automatically freeing
   313  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   314  * you could do:
   315  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   316  *
   317  * If this function succeeds, it returns the given SDL_AudioSpec,
   318  * filled with the audio data format of the wave data, and sets
   319  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   320  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   321  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   322  * done with it.
   323  *
   324  * This function returns NULL and sets the SDL error message if the 
   325  * wave file cannot be opened, uses an unknown data format, or is 
   326  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   327  */
   328 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
   329                                                       int freesrc,
   330                                                       SDL_AudioSpec * spec,
   331                                                       Uint8 ** audio_buf,
   332                                                       Uint32 * audio_len);
   333 
   334 /* Compatibility convenience function -- loads a WAV from a file */
   335 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   336 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   337 
   338 /*
   339  * This function frees data previously allocated with SDL_LoadWAV_RW()
   340  */
   341 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
   342 
   343 /*
   344  * This function takes a source format and rate and a destination format
   345  * and rate, and initializes the 'cvt' structure with information needed
   346  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   347  * to the other.
   348  * Returns -1 if the format conversion is not supported, 0 if there's
   349  *  no conversion needed, or 1 if the audio filter is set up.
   350  */
   351 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
   352                                               SDL_AudioFormat src_format,
   353                                               Uint8 src_channels,
   354                                               int src_rate,
   355                                               SDL_AudioFormat dst_format,
   356                                               Uint8 dst_channels,
   357                                               int dst_rate);
   358 
   359 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   360  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   361  * audio data in the source format, this function will convert it in-place
   362  * to the desired format.
   363  * The data conversion may expand the size of the audio data, so the buffer
   364  * cvt->buf should be allocated after the cvt structure is initialized by
   365  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   366  */
   367 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
   368 
   369 /*
   370  * This takes two audio buffers of the playing audio format and mixes
   371  * them, performing addition, volume adjustment, and overflow clipping.
   372  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   373  * for full audio volume.  Note this does not change hardware volume.
   374  * This is provided for convenience -- you can mix your own audio data.
   375  */
   376 #define SDL_MIX_MAXVOLUME 128
   377 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
   378                                           Uint32 len, int volume);
   379 
   380 /*
   381  * This works like SDL_MixAudio, but you specify the audio format instead of
   382  *  using the format of audio device 1. Thus it can be used when no audio
   383  *  device is open at all.
   384  */
   385 extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
   386                                                 const Uint8 * src,
   387                                                 SDL_AudioFormat format,
   388                                                 Uint32 len, int volume);
   389 
   390 /*
   391  * The lock manipulated by these functions protects the callback function.
   392  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   393  * callback function is not running.  Do not call these from the callback
   394  * function or you will cause deadlock.
   395  */
   396 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   397 extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
   398 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   399 extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
   400 
   401 /*
   402  * This function shuts down audio processing and closes the audio device.
   403  */
   404 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   405 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
   406 
   407 /*
   408  * Returns 1 if audio device is still functioning, zero if not, -1 on error.
   409  */
   410 extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
   411 
   412 
   413 /* Ends C function definitions when using C++ */
   414 #ifdef __cplusplus
   415 /* *INDENT-OFF* */
   416 }
   417 /* *INDENT-ON* */
   418 #endif
   419 #include "close_code.h"
   420 
   421 #endif /* _SDL_audio_h */
   422 
   423 /* vi: set ts=4 sw=4 expandtab: */