include/SDL_audio.h
author Sam Lantinga <slouken@libsdl.org>
Mon, 29 May 2006 04:04:35 +0000
branchSDL-1.3
changeset 1668 4da1ee79c9af
parent 1662 782fd950bd46
permissions -rw-r--r--
more tweaking indent options
     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 /* The calculated values in this structure are calculated by SDL_OpenAudio() */
    48 typedef struct SDL_AudioSpec
    49 {
    50     int freq;                   /* DSP frequency -- samples per second */
    51     Uint16 format;              /* Audio data format */
    52     Uint8 channels;             /* Number of channels: 1 mono, 2 stereo */
    53     Uint8 silence;              /* Audio buffer silence value (calculated) */
    54     Uint16 samples;             /* Audio buffer size in samples (power of 2) */
    55     Uint16 padding;             /* Necessary for some compile environments */
    56     Uint32 size;                /* Audio buffer size in bytes (calculated) */
    57     /* This function is called when the audio device needs more data.
    58        'stream' is a pointer to the audio data buffer
    59        'len' is the length of that buffer in bytes.
    60        Once the callback returns, the buffer will no longer be valid.
    61        Stereo samples are stored in a LRLRLR ordering.
    62      */
    63     void (SDLCALL * callback) (void *userdata, Uint8 * stream, int len);
    64     void *userdata;
    65 } SDL_AudioSpec;
    66 
    67 /* Audio format flags (defaults to LSB byte order) */
    68 #define AUDIO_U8	0x0008  /* Unsigned 8-bit samples */
    69 #define AUDIO_S8	0x8008  /* Signed 8-bit samples */
    70 #define AUDIO_U16LSB	0x0010  /* Unsigned 16-bit samples */
    71 #define AUDIO_S16LSB	0x8010  /* Signed 16-bit samples */
    72 #define AUDIO_U16MSB	0x1010  /* As above, but big-endian byte order */
    73 #define AUDIO_S16MSB	0x9010  /* As above, but big-endian byte order */
    74 #define AUDIO_U16	AUDIO_U16LSB
    75 #define AUDIO_S16	AUDIO_S16LSB
    76 
    77 /* Native audio byte ordering */
    78 #if SDL_BYTEORDER == SDL_LIL_ENDIAN
    79 #define AUDIO_U16SYS	AUDIO_U16LSB
    80 #define AUDIO_S16SYS	AUDIO_S16LSB
    81 #else
    82 #define AUDIO_U16SYS	AUDIO_U16MSB
    83 #define AUDIO_S16SYS	AUDIO_S16MSB
    84 #endif
    85 
    86 
    87 /* A structure to hold a set of audio conversion filters and buffers */
    88 typedef struct SDL_AudioCVT
    89 {
    90     int needed;                 /* Set to 1 if conversion possible */
    91     Uint16 src_format;          /* Source audio format */
    92     Uint16 dst_format;          /* Target audio format */
    93     double rate_incr;           /* Rate conversion increment */
    94     Uint8 *buf;                 /* Buffer to hold entire audio data */
    95     int len;                    /* Length of original audio buffer */
    96     int len_cvt;                /* Length of converted audio buffer */
    97     int len_mult;               /* buffer must be len*len_mult big */
    98     double len_ratio;           /* Given len, final size is len*len_ratio */
    99     void (SDLCALL * filters[10]) (struct SDL_AudioCVT * cvt, Uint16 format);
   100     int filter_index;           /* Current audio conversion function */
   101 } SDL_AudioCVT;
   102 
   103 
   104 /* Function prototypes */
   105 
   106 /* These functions return the list of built in video drivers, in the 
   107  * order that they are normally initialized by default.
   108  */
   109 extern DECLSPEC int SDLCALL SDL_GetNumAudioDrivers(void);
   110 extern DECLSPEC const char *SDLCALL SDL_GetAudioDriver(int index);
   111 
   112 /* These functions are used internally, and should not be used unless you
   113  * have a specific need to specify the audio driver you want to use.
   114  * You should normally use SDL_Init() or SDL_InitSubSystem().
   115  */
   116 extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
   117 extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
   118 
   119 /* This function returns the name of the current audio driver, or NULL
   120  * if no driver has been initialized.
   121  */
   122 extern DECLSPEC const char *SDLCALL SDL_GetCurrentAudioDriver(void);
   123 
   124 /*
   125  * This function opens the audio device with the desired parameters, and
   126  * returns 0 if successful, placing the actual hardware parameters in the
   127  * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
   128  * data passed to the callback function will be guaranteed to be in the
   129  * requested format, and will be automatically converted to the hardware
   130  * audio format if necessary.  This function returns -1 if it failed 
   131  * to open the audio device, or couldn't set up the audio thread.
   132  *
   133  * When filling in the desired audio spec structure,
   134  *  'desired->freq' should be the desired audio frequency in samples-per-second.
   135  *  'desired->format' should be the desired audio format.
   136  *  'desired->samples' is the desired size of the audio buffer, in samples.
   137  *     This number should be a power of two, and may be adjusted by the audio
   138  *     driver to a value more suitable for the hardware.  Good values seem to
   139  *     range between 512 and 8096 inclusive, depending on the application and
   140  *     CPU speed.  Smaller values yield faster response time, but can lead
   141  *     to underflow if the application is doing heavy processing and cannot
   142  *     fill the audio buffer in time.  A stereo sample consists of both right
   143  *     and left channels in LR ordering.
   144  *     Note that the number of samples is directly related to time by the
   145  *     following formula:  ms = (samples*1000)/freq
   146  *  'desired->size' is the size in bytes of the audio buffer, and is
   147  *     calculated by SDL_OpenAudio().
   148  *  'desired->silence' is the value used to set the buffer to silence,
   149  *     and is calculated by SDL_OpenAudio().
   150  *  'desired->callback' should be set to a function that will be called
   151  *     when the audio device is ready for more data.  It is passed a pointer
   152  *     to the audio buffer, and the length in bytes of the audio buffer.
   153  *     This function usually runs in a separate thread, and so you should
   154  *     protect data structures that it accesses by calling SDL_LockAudio()
   155  *     and SDL_UnlockAudio() in your code.
   156  *  'desired->userdata' is passed as the first parameter to your callback
   157  *     function.
   158  *
   159  * The audio device starts out playing silence when it's opened, and should
   160  * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
   161  * for your audio callback function to be called.  Since the audio driver
   162  * may modify the requested size of the audio buffer, you should allocate
   163  * any local mixing buffers after you open the audio device.
   164  */
   165 extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec * desired,
   166                                           SDL_AudioSpec * obtained);
   167 
   168 /*
   169  * Get the current audio state:
   170  */
   171 typedef enum
   172 {
   173     SDL_AUDIO_STOPPED = 0,
   174     SDL_AUDIO_PLAYING,
   175     SDL_AUDIO_PAUSED
   176 } SDL_audiostatus;
   177 extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
   178 
   179 /*
   180  * This function pauses and unpauses the audio callback processing.
   181  * It should be called with a parameter of 0 after opening the audio
   182  * device to start playing sound.  This is so you can safely initialize
   183  * data for your callback function after opening the audio device.
   184  * Silence will be written to the audio device during the pause.
   185  */
   186 extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
   187 
   188 /*
   189  * This function loads a WAVE from the data source, automatically freeing
   190  * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
   191  * you could do:
   192  *	SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...);
   193  *
   194  * If this function succeeds, it returns the given SDL_AudioSpec,
   195  * filled with the audio data format of the wave data, and sets
   196  * 'audio_buf' to a malloc()'d buffer containing the audio data,
   197  * and sets 'audio_len' to the length of that audio buffer, in bytes.
   198  * You need to free the audio buffer with SDL_FreeWAV() when you are 
   199  * done with it.
   200  *
   201  * This function returns NULL and sets the SDL error message if the 
   202  * wave file cannot be opened, uses an unknown data format, or is 
   203  * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
   204  */
   205 extern DECLSPEC SDL_AudioSpec *SDLCALL SDL_LoadWAV_RW(SDL_RWops * src,
   206                                                       int freesrc,
   207                                                       SDL_AudioSpec * spec,
   208                                                       Uint8 ** audio_buf,
   209                                                       Uint32 * audio_len);
   210 
   211 /* Compatibility convenience function -- loads a WAV from a file */
   212 #define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
   213 	SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
   214 
   215 /*
   216  * This function frees data previously allocated with SDL_LoadWAV_RW()
   217  */
   218 extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 * audio_buf);
   219 
   220 /*
   221  * This function takes a source format and rate and a destination format
   222  * and rate, and initializes the 'cvt' structure with information needed
   223  * by SDL_ConvertAudio() to convert a buffer of audio data from one format
   224  * to the other.
   225  * This function returns 0, or -1 if there was an error.
   226  */
   227 extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT * cvt,
   228                                               Uint16 src_format,
   229                                               Uint8 src_channels,
   230                                               int src_rate,
   231                                               Uint16 dst_format,
   232                                               Uint8 dst_channels,
   233                                               int dst_rate);
   234 
   235 /* Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
   236  * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
   237  * audio data in the source format, this function will convert it in-place
   238  * to the desired format.
   239  * The data conversion may expand the size of the audio data, so the buffer
   240  * cvt->buf should be allocated after the cvt structure is initialized by
   241  * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
   242  */
   243 extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT * cvt);
   244 
   245 /*
   246  * This takes two audio buffers of the playing audio format and mixes
   247  * them, performing addition, volume adjustment, and overflow clipping.
   248  * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
   249  * for full audio volume.  Note this does not change hardware volume.
   250  * This is provided for convenience -- you can mix your own audio data.
   251  */
   252 #define SDL_MIX_MAXVOLUME 128
   253 extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 * dst, const Uint8 * src,
   254                                           Uint32 len, int volume);
   255 
   256 /*
   257  * The lock manipulated by these functions protects the callback function.
   258  * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
   259  * callback function is not running.  Do not call these from the callback
   260  * function or you will cause deadlock.
   261  */
   262 extern DECLSPEC void SDLCALL SDL_LockAudio(void);
   263 extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
   264 
   265 /*
   266  * This function shuts down audio processing and closes the audio device.
   267  */
   268 extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
   269 
   270 
   271 /* Ends C function definitions when using C++ */
   272 #ifdef __cplusplus
   273 /* *INDENT-OFF* */
   274 }
   275 /* *INDENT-ON* */
   276 #endif
   277 #include "close_code.h"
   278 
   279 #endif /* _SDL_audio_h */
   280 
   281 /* vi: set ts=4 sw=4 expandtab: */