include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Sat, 13 Dec 2008 06:36:47 +0000
changeset 2866 e532417a6977
parent 2859 99210400e8b9
child 3021 f3dcf04412cf
permissions -rw-r--r--
Fixed SDL 1.2 compatibility problem.

The API specifies that SDL_OpenAudio() will fill out the 'desired' audio spec
with the correct samples and size set by the driver. This value is important
since it may be used by applications that size audio buffers, etc.

However, we want to allow advanced applications to call SDL_OpenAudioDevice()
which gets passed a const 'desired' parameter, and have the correct data filled
into the 'obtained' parameter, possibly allowing or not allowing format changes.

So... 'obtained' becomes the audio format the user callback is expected to use,
and we add flags to allow the application to specify which format changes are
allowed.

Note: We really need to add a way to query the 'obtained' audio spec.
     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     Uint8 *coeff;               /* Filter coefficients: either big windowed sinc filter, or 6 IIR lowpass coefficients */
   151     Uint8 *state_buf;           /* Sample history for either the FIR or IIR filter. For IIR filter, first two elements are X, second two are Y, and state_pos toggles the order */
   152     int state_pos;              /* Position in the state */
   153     int len_sinc;               /* Length of windowed sinc filter, in appropriate units (not necessarily bytes) */
   154     int len;                    /* Length of original audio buffer */
   155     int len_cvt;                /* Length of converted audio buffer */
   156     int len_mult;               /* buffer must be len*len_mult big */
   157     int len_div;                /* destination length = len_mult / len_div * src length */
   158     double len_ratio;           /* Given len, final size is len*len_ratio ( len_ratio = len_mult / len_div ) */
   159     SDL_AudioFilter filters[10];        /* Filter list */
   160     int filter_index;           /* Current audio conversion function */
   161 } SDL_AudioCVT;
   162 
   163 
   164 /* Function prototypes */
   165 
   166 /* These functions return the list of built in audio drivers, in the
   167  * order that they are normally initialized by default.
   168  */
   169 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
   170 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
   171 
   172 /* These functions are used internally, and should not be used unless you
   173  * have a specific need to specify the audio driver you want to use.
   174  * You should normally use SDL_Init() or SDL_InitSubSystem().
   175  */
   176 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   177 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   178 
   179 /* This function returns the name of the current audio driver, or NULL
   180  * if no driver has been initialized.
   181  */
   182 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
   183 
   184 /*
   185  * This function opens the audio device with the desired parameters, and
   186  * returns 0 if successful, placing the actual hardware parameters in the
   187  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   188  * data passed to the callback function will be guaranteed to be in the
   189  * requested format, and will be automatically converted to the hardware
   190  * audio format if necessary.  This function returns -1 if it failed 
   191  * to open the audio device, or couldn't set up the audio thread.
   192  *
   193  * When filling in the desired audio spec structure,
   194  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   195  *  'desired->format' should be the desired audio format.
   196  *  'desired->samples' is the desired size of the audio buffer, in samples.
   197  *     This number should be a power of two, and may be adjusted by the audio
   198  *     driver to a value more suitable for the hardware.  Good values seem to
   199  *     range between 512 and 8096 inclusive, depending on the application and
   200  *     CPU speed.  Smaller values yield faster response time, but can lead
   201  *     to underflow if the application is doing heavy processing and cannot
   202  *     fill the audio buffer in time.  A stereo sample consists of both right
   203  *     and left channels in LR ordering.
   204  *     Note that the number of samples is directly related to time by the
   205  *     following formula:  ms = (samples*1000)/freq
   206  *  'desired->size' is the size in bytes of the audio buffer, and is
   207  *     calculated by SDL_OpenAudio().
   208  *  'desired->silence' is the value used to set the buffer to silence,
   209  *     and is calculated by SDL_OpenAudio().
   210  *  'desired->callback' should be set to a function that will be called
   211  *     when the audio device is ready for more data.  It is passed a pointer
   212  *     to the audio buffer, and the length in bytes of the audio buffer.
   213  *     This function usually runs in a separate thread, and so you should
   214  *     protect data structures that it accesses by calling SDL_LockAudio()
   215  *     and SDL_UnlockAudio() in your code.
   216  *  'desired->userdata' is passed as the first parameter to your callback
   217  *     function.
   218  *
   219  * The audio device starts out playing silence when it's opened, and should
   220  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   221  * for your audio callback function to be called.  Since the audio driver
   222  * may modify the requested size of the audio buffer, you should allocate
   223  * any local mixing buffers after you open the audio device.
   224  */
   225 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
   226                                           SDL_AudioSpec * obtained);
   227 
   228 /*
   229  * SDL Audio Device IDs.
   230  * A successful call to SDL_OpenAudio() is always device id 1, and legacy
   231  *  SDL audio APIs assume you want this device ID. SDL_OpenAudioDevice() calls
   232  *  always returns devices >= 2 on success. The legacy calls are good both
   233  *  for backwards compatibility and when you don't care about multiple,
   234  *  specific, or capture devices.
   235  */
   236 typedef Uint32 SDL_AudioDeviceID;
   237 
   238 /*
   239  * Get the number of available devices exposed by the current driver.
   240  *  Only valid after a successfully initializing the audio subsystem.
   241  *  Returns -1 if an explicit list of devices can't be determined; this is
   242  *  not an error. For example, if SDL is set up to talk to a remote audio
   243  *  server, it can't list every one available on the Internet, but it will
   244  *  still allow a specific host to be specified to SDL_OpenAudioDevice().
   245  * In many common cases, when this function returns a value <= 0, it can still
   246  *  successfully open the default device (NULL for first argument of
   247  *  SDL_OpenAudioDevice()).
   248  */
   249 extern DECLSPEC int SDLCALL SDL_GetNumAudioDevices(int iscapture);
   250 
   251 /*
   252  * Get the human-readable name of a specific audio device.
   253  *  Must be a value between 0 and (number of audio devices-1).
   254  *  Only valid after a successfully initializing the audio subsystem.
   255  *  The values returned by this function reflect the latest call to
   256  *  SDL_GetNumAudioDevices(); recall that function to redetect available
   257  *  hardware.
   258  *
   259  * The string returned by this function is UTF-8 encoded, read-only, and
   260  *  managed internally. You are not to free it. If you need to keep the
   261  *  string for any length of time, you should make your own copy of it, as it
   262  *  will be invalid next time any of several other SDL functions is called.
   263  */
   264 extern DECLSPEC const char *SDLCALL SDL_GetAudioDeviceName(int index,
   265                                                            int iscapture);
   266 
   267 
   268 /*
   269  * Open a specific audio device. Passing in a device name of NULL requests
   270  *  the most reasonable default (and is equivalent to calling SDL_OpenAudio()).
   271  * The device name is a UTF-8 string reported by SDL_GetAudioDevice(), but
   272  *  some drivers allow arbitrary and driver-specific strings, such as a
   273  *  hostname/IP address for a remote audio server, or a filename in the
   274  *  diskaudio driver.
   275  * Returns 0 on error, a valid device ID that is >= 2 on success.
   276  *  SDL_OpenAudio(), unlike this function, always acts on device ID 1.
   277  */
   278 extern DECLSPEC SDL_AudioDeviceID SDLCALL SDL_OpenAudioDevice(const char
   279                                                               *device,
   280                                                               int iscapture,
   281                                                               const
   282                                                               SDL_AudioSpec *
   283                                                               desired,
   284                                                               SDL_AudioSpec *
   285                                                               obtained,
   286                                                               int
   287                                                               allowed_changes);
   288 
   289 
   290 
   291 /*
   292  * Get the current audio state:
   293  */
   294 typedef enum
   295 {
   296     SDL_AUDIO_STOPPED = 0,
   297     SDL_AUDIO_PLAYING,
   298     SDL_AUDIO_PAUSED
   299 } SDL_audiostatus;
   300 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   301 
   302 extern DECLSPEC SDL_audiostatus SDLCALL
   303 SDL_GetAudioDeviceStatus(SDL_AudioDeviceID dev);
   304 
   305 /*
   306  * This function pauses and unpauses the audio callback processing.
   307  * It should be called with a parameter of 0 after opening the audio
   308  * device to start playing sound.  This is so you can safely initialize
   309  * data for your callback function after opening the audio device.
   310  * Silence will be written to the audio device during the pause.
   311  */
   312 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   313 extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
   314                                                   int pause_on);
   315 
   316 /*
   317  * This function loads a WAVE from the data source, automatically freeing
   318  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   319  * you could do:
   320  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   321  *
   322  * If this function succeeds, it returns the given SDL_AudioSpec,
   323  * filled with the audio data format of the wave data, and sets
   324  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   325  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   326  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   327  * done with it.
   328  *
   329  * This function returns NULL and sets the SDL error message if the 
   330  * wave file cannot be opened, uses an unknown data format, or is 
   331  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   332  */
   333 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
   334                                                       int freesrc,
   335                                                       SDL_AudioSpec * spec,
   336                                                       Uint8 ** audio_buf,
   337                                                       Uint32 * audio_len);
   338 
   339 /* Compatibility convenience function -- loads a WAV from a file */
   340 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   341 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   342 
   343 /*
   344  * This function frees data previously allocated with SDL_LoadWAV_RW()
   345  */
   346 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
   347 
   348 /*
   349  * This function takes a source format and rate and a destination format
   350  * and rate, and initializes the 'cvt' structure with information needed
   351  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   352  * to the other.
   353  * Returns -1 if the format conversion is not supported, 0 if there's
   354  *  no conversion needed, or 1 if the audio filter is set up.
   355  */
   356 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
   357                                               SDL_AudioFormat src_format,
   358                                               Uint8 src_channels,
   359                                               int src_rate,
   360                                               SDL_AudioFormat dst_format,
   361                                               Uint8 dst_channels,
   362                                               int dst_rate);
   363 
   364 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   365  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   366  * audio data in the source format, this function will convert it in-place
   367  * to the desired format.
   368  * The data conversion may expand the size of the audio data, so the buffer
   369  * cvt->buf should be allocated after the cvt structure is initialized by
   370  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   371  */
   372 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
   373 
   374 /*
   375  * This takes two audio buffers of the playing audio format and mixes
   376  * them, performing addition, volume adjustment, and overflow clipping.
   377  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   378  * for full audio volume.  Note this does not change hardware volume.
   379  * This is provided for convenience -- you can mix your own audio data.
   380  */
   381 #define SDL_MIX_MAXVOLUME 128
   382 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
   383                                           Uint32 len, int volume);
   384 
   385 /*
   386  * This works like SDL_MixAudio, but you specify the audio format instead of
   387  *  using the format of audio device 1. Thus it can be used when no audio
   388  *  device is open at all.
   389  */
   390 extern DECLSPEC void SDLCALL SDL_MixAudioFormat(Uint8 * dst,
   391                                                 const Uint8 * src,
   392                                                 SDL_AudioFormat format,
   393                                                 Uint32 len, int volume);
   394 
   395 /*
   396  * The lock manipulated by these functions protects the callback function.
   397  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   398  * callback function is not running.  Do not call these from the callback
   399  * function or you will cause deadlock.
   400  */
   401 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   402 extern DECLSPEC void SDLCALL SDL_LockAudioDevice(SDL_AudioDeviceID dev);
   403 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   404 extern DECLSPEC void SDLCALL SDL_UnlockAudioDevice(SDL_AudioDeviceID dev);
   405 
   406 /*
   407  * This function shuts down audio processing and closes the audio device.
   408  */
   409 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   410 extern DECLSPEC void SDLCALL SDL_CloseAudioDevice(SDL_AudioDeviceID dev);
   411 
   412 /*
   413  * Returns 1 if audio device is still functioning, zero if not, -1 on error.
   414  */
   415 extern DECLSPEC int SDLCALL SDL_AudioDeviceConnected(SDL_AudioDeviceID dev);
   416 
   417 
   418 /* Ends C function definitions when using C++ */
   419 #ifdef __cplusplus
   420 /* *INDENT-OFF* */
   421 }
   422 /* *INDENT-ON* */
   423 #endif
   424 #include "close_code.h"
   425 
   426 #endif /* _SDL_audio_h */
   427 
   428 /* vi: set ts=4 sw=4 expandtab: */