source: trunk/external/sdl-1.2.15/include/SDL_audio.h @ 2214

Last change on this file since 2214 was 1586, checked in by sam, 9 years ago

build: update Windows SDL binaries to 1.2.15.

File size: 11.0 KB
Line 
1/*
2    SDL - Simple DirectMedia Layer
3    Copyright (C) 1997-2012 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 *  Access to the raw audio mixing buffer for the SDL library
26 */
27
28#ifndef _SDL_audio_h
29#define _SDL_audio_h
30
31#include "SDL_stdinc.h"
32#include "SDL_error.h"
33#include "SDL_endian.h"
34#include "SDL_mutex.h"
35#include "SDL_thread.h"
36#include "SDL_rwops.h"
37
38#include "begin_code.h"
39/* Set up for C function definitions, even when using C++ */
40#ifdef __cplusplus
41extern "C" {
42#endif
43
44/**
45 * When filling in the desired audio spec structure,
46 * - 'desired->freq' should be the desired audio frequency in samples-per-second.
47 * - 'desired->format' should be the desired audio format.
48 * - 'desired->samples' is the desired size of the audio buffer, in samples.
49 *     This number should be a power of two, and may be adjusted by the audio
50 *     driver to a value more suitable for the hardware.  Good values seem to
51 *     range between 512 and 8096 inclusive, depending on the application and
52 *     CPU speed.  Smaller values yield faster response time, but can lead
53 *     to underflow if the application is doing heavy processing and cannot
54 *     fill the audio buffer in time.  A stereo sample consists of both right
55 *     and left channels in LR ordering.
56 *     Note that the number of samples is directly related to time by the
57 *     following formula:  ms = (samples*1000)/freq
58 * - 'desired->size' is the size in bytes of the audio buffer, and is
59 *     calculated by SDL_OpenAudio().
60 * - 'desired->silence' is the value used to set the buffer to silence,
61 *     and is calculated by SDL_OpenAudio().
62 * - 'desired->callback' should be set to a function that will be called
63 *     when the audio device is ready for more data.  It is passed a pointer
64 *     to the audio buffer, and the length in bytes of the audio buffer.
65 *     This function usually runs in a separate thread, and so you should
66 *     protect data structures that it accesses by calling SDL_LockAudio()
67 *     and SDL_UnlockAudio() in your code.
68 * - 'desired->userdata' is passed as the first parameter to your callback
69 *     function.
70 *
71 * @note The calculated values in this structure are calculated by SDL_OpenAudio()
72 *
73 */
74typedef struct SDL_AudioSpec {
75        int freq;               /**< DSP frequency -- samples per second */
76        Uint16 format;          /**< Audio data format */
77        Uint8  channels;        /**< Number of channels: 1 mono, 2 stereo */
78        Uint8  silence;         /**< Audio buffer silence value (calculated) */
79        Uint16 samples;         /**< Audio buffer size in samples (power of 2) */
80        Uint16 padding;         /**< Necessary for some compile environments */
81        Uint32 size;            /**< Audio buffer size in bytes (calculated) */
82        /**
83         *  This function is called when the audio device needs more data.
84         *
85         *  @param[out] stream  A pointer to the audio data buffer
86         *  @param[in]  len     The length of the audio buffer in bytes.
87         *
88         *  Once the callback returns, the buffer will no longer be valid.
89         *  Stereo samples are stored in a LRLRLR ordering.
90         */
91        void (SDLCALL *callback)(void *userdata, Uint8 *stream, int len);
92        void  *userdata;
93} SDL_AudioSpec;
94
95/**
96 *  @name Audio format flags
97 *  defaults to LSB byte order
98 */
99/*@{*/
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/**
110 *  @name Native audio byte ordering
111 */
112/*@{*/
113#if SDL_BYTEORDER == SDL_LIL_ENDIAN
114#define AUDIO_U16SYS    AUDIO_U16LSB
115#define AUDIO_S16SYS    AUDIO_S16LSB
116#else
117#define AUDIO_U16SYS    AUDIO_U16MSB
118#define AUDIO_S16SYS    AUDIO_S16MSB
119#endif
120/*@}*/
121
122/*@}*/
123
124
125/** A structure to hold a set of audio conversion filters and buffers */
126typedef struct SDL_AudioCVT {
127        int needed;                     /**< Set to 1 if conversion possible */
128        Uint16 src_format;              /**< Source audio format */
129        Uint16 dst_format;              /**< Target audio format */
130        double rate_incr;               /**< Rate conversion increment */
131        Uint8 *buf;                     /**< Buffer to hold entire audio data */
132        int    len;                     /**< Length of original audio buffer */
133        int    len_cvt;                 /**< Length of converted audio buffer */
134        int    len_mult;                /**< buffer must be len*len_mult big */
135        double len_ratio;       /**< Given len, final size is len*len_ratio */
136        void (SDLCALL *filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
137        int filter_index;               /**< Current audio conversion function */
138} SDL_AudioCVT;
139
140
141/* Function prototypes */
142
143/**
144 * @name Audio Init and Quit
145 * These functions are used internally, and should not be used unless you
146 * have a specific need to specify the audio driver you want to use.
147 * You should normally use SDL_Init() or SDL_InitSubSystem().
148 */
149/*@{*/
150extern DECLSPEC int SDLCALL SDL_AudioInit(const char *driver_name);
151extern DECLSPEC void SDLCALL SDL_AudioQuit(void);
152/*@}*/
153
154/**
155 * This function fills the given character buffer with the name of the
156 * current audio driver, and returns a pointer to it if the audio driver has
157 * been initialized.  It returns NULL if no driver has been initialized.
158 */
159extern DECLSPEC char * SDLCALL SDL_AudioDriverName(char *namebuf, int maxlen);
160
161/**
162 * This function opens the audio device with the desired parameters, and
163 * returns 0 if successful, placing the actual hardware parameters in the
164 * structure pointed to by 'obtained'.  If 'obtained' is NULL, the audio
165 * data passed to the callback function will be guaranteed to be in the
166 * requested format, and will be automatically converted to the hardware
167 * audio format if necessary.  This function returns -1 if it failed
168 * to open the audio device, or couldn't set up the audio thread.
169 *
170 * The audio device starts out playing silence when it's opened, and should
171 * be enabled for playing by calling SDL_PauseAudio(0) when you are ready
172 * for your audio callback function to be called.  Since the audio driver
173 * may modify the requested size of the audio buffer, you should allocate
174 * any local mixing buffers after you open the audio device.
175 *
176 * @sa SDL_AudioSpec
177 */
178extern DECLSPEC int SDLCALL SDL_OpenAudio(SDL_AudioSpec *desired, SDL_AudioSpec *obtained);
179
180typedef enum {
181        SDL_AUDIO_STOPPED = 0,
182        SDL_AUDIO_PLAYING,
183        SDL_AUDIO_PAUSED
184} SDL_audiostatus;
185
186/** Get the current audio state */
187extern DECLSPEC SDL_audiostatus SDLCALL SDL_GetAudioStatus(void);
188
189/**
190 * This function pauses and unpauses the audio callback processing.
191 * It should be called with a parameter of 0 after opening the audio
192 * device to start playing sound.  This is so you can safely initialize
193 * data for your callback function after opening the audio device.
194 * Silence will be written to the audio device during the pause.
195 */
196extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
197
198/**
199 * This function loads a WAVE from the data source, automatically freeing
200 * that source if 'freesrc' is non-zero.  For example, to load a WAVE file,
201 * you could do:
202 *      @code SDL_LoadWAV_RW(SDL_RWFromFile("sample.wav", "rb"), 1, ...); @endcode
203 *
204 * If this function succeeds, it returns the given SDL_AudioSpec,
205 * filled with the audio data format of the wave data, and sets
206 * 'audio_buf' to a malloc()'d buffer containing the audio data,
207 * and sets 'audio_len' to the length of that audio buffer, in bytes.
208 * You need to free the audio buffer with SDL_FreeWAV() when you are
209 * done with it.
210 *
211 * This function returns NULL and sets the SDL error message if the
212 * wave file cannot be opened, uses an unknown data format, or is
213 * corrupt.  Currently raw and MS-ADPCM WAVE files are supported.
214 */
215extern DECLSPEC SDL_AudioSpec * SDLCALL SDL_LoadWAV_RW(SDL_RWops *src, int freesrc, SDL_AudioSpec *spec, Uint8 **audio_buf, Uint32 *audio_len);
216
217/** Compatibility convenience function -- loads a WAV from a file */
218#define SDL_LoadWAV(file, spec, audio_buf, audio_len) \
219        SDL_LoadWAV_RW(SDL_RWFromFile(file, "rb"),1, spec,audio_buf,audio_len)
220
221/**
222 * This function frees data previously allocated with SDL_LoadWAV_RW()
223 */
224extern DECLSPEC void SDLCALL SDL_FreeWAV(Uint8 *audio_buf);
225
226/**
227 * This function takes a source format and rate and a destination format
228 * and rate, and initializes the 'cvt' structure with information needed
229 * by SDL_ConvertAudio() to convert a buffer of audio data from one format
230 * to the other.
231 *
232 * @return This function returns 0, or -1 if there was an error.
233 */
234extern DECLSPEC int SDLCALL SDL_BuildAudioCVT(SDL_AudioCVT *cvt,
235                Uint16 src_format, Uint8 src_channels, int src_rate,
236                Uint16 dst_format, Uint8 dst_channels, int dst_rate);
237
238/**
239 * Once you have initialized the 'cvt' structure using SDL_BuildAudioCVT(),
240 * created an audio buffer cvt->buf, and filled it with cvt->len bytes of
241 * audio data in the source format, this function will convert it in-place
242 * to the desired format.
243 * The data conversion may expand the size of the audio data, so the buffer
244 * cvt->buf should be allocated after the cvt structure is initialized by
245 * SDL_BuildAudioCVT(), and should be cvt->len*cvt->len_mult bytes long.
246 */
247extern DECLSPEC int SDLCALL SDL_ConvertAudio(SDL_AudioCVT *cvt);
248
249
250#define SDL_MIX_MAXVOLUME 128
251/**
252 * This takes two audio buffers of the playing audio format and mixes
253 * them, performing addition, volume adjustment, and overflow clipping.
254 * The volume ranges from 0 - 128, and should be set to SDL_MIX_MAXVOLUME
255 * for full audio volume.  Note this does not change hardware volume.
256 * This is provided for convenience -- you can mix your own audio data.
257 */
258extern DECLSPEC void SDLCALL SDL_MixAudio(Uint8 *dst, const Uint8 *src, Uint32 len, int volume);
259
260/**
261 * @name Audio Locks
262 * The lock manipulated by these functions protects the callback function.
263 * During a LockAudio/UnlockAudio pair, you can be guaranteed that the
264 * callback function is not running.  Do not call these from the callback
265 * function or you will cause deadlock.
266 */
267/*@{*/
268extern DECLSPEC void SDLCALL SDL_LockAudio(void);
269extern DECLSPEC void SDLCALL SDL_UnlockAudio(void);
270/*@}*/
271
272/**
273 * This function shuts down audio processing and closes the audio device.
274 */
275extern DECLSPEC void SDLCALL SDL_CloseAudio(void);
276
277
278/* Ends C function definitions when using C++ */
279#ifdef __cplusplus
280}
281#endif
282#include "close_code.h"
283
284#endif /* _SDL_audio_h */
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