SDL_sysaudio.h
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/*
Simple DirectMedia Layer
Copyright (C) 1997-2014 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "../SDL_internal.h"
#ifndef _SDL_sysaudio_h
#define _SDL_sysaudio_h
#include "SDL_mutex.h"
#include "SDL_thread.h"
/* The SDL audio driver */
typedef struct SDL_AudioDevice SDL_AudioDevice;
#define _THIS SDL_AudioDevice *_this
/* Used by audio targets during DetectDevices() */
typedef void (*SDL_AddAudioDevice)(const char *name);
/* This is the size of a packet when using SDL_QueueAudio(). We allocate
these as necessary and pool them, under the assumption that we'll
eventually end up with a handful that keep recycling, meeting whatever
the app needs. We keep packing data tightly as more arrives to avoid
wasting space, and if we get a giant block of data, we'll split them
into multiple packets behind the scenes. My expectation is that most
apps will have 2-3 of these in the pool. 8k should cover most needs, but
if this is crippling for some embedded system, we can #ifdef this.
The system preallocates enough packets for 2 callbacks' worth of data. */
#define SDL_AUDIOBUFFERQUEUE_PACKETLEN (8 * 1024)
/* Used by apps that queue audio instead of using the callback. */
typedef struct SDL_AudioBufferQueue
{
Uint8 data[SDL_AUDIOBUFFERQUEUE_PACKETLEN]; /* packet data. */
Uint32 datalen; /* bytes currently in use in this packet. */
Uint32 startpos; /* bytes currently consumed in this packet. */
struct SDL_AudioBufferQueue *next; /* next item in linked list. */
} SDL_AudioBufferQueue;
typedef struct SDL_AudioDriverImpl
{
void (*DetectDevices) (int iscapture, SDL_AddAudioDevice addfn);
int (*OpenDevice) (_THIS, const char *devname, int iscapture);
void (*ThreadInit) (_THIS); /* Called by audio thread at start */
void (*WaitDevice) (_THIS);
void (*PlayDevice) (_THIS);
int (*GetPendingBytes) (_THIS);
Uint8 *(*GetDeviceBuf) (_THIS);
void (*WaitDone) (_THIS);
void (*CloseDevice) (_THIS);
void (*LockDevice) (_THIS);
void (*UnlockDevice) (_THIS);
void (*Deinitialize) (void);
/* !!! FIXME: add pause(), so we can optimize instead of mixing silence. */
/* Some flags to push duplicate code into the core and reduce #ifdefs. */
int ProvidesOwnCallbackThread;
int SkipMixerLock; /* !!! FIXME: do we need this anymore? */
int HasCaptureSupport;
int OnlyHasDefaultOutputDevice;
int OnlyHasDefaultInputDevice;
} SDL_AudioDriverImpl;
typedef struct SDL_AudioDriver
{
/* * * */
/* The name of this audio driver */
const char *name;
/* * * */
/* The description of this audio driver */
const char *desc;
SDL_AudioDriverImpl impl;
char **outputDevices;
int outputDeviceCount;
char **inputDevices;
int inputDeviceCount;
} SDL_AudioDriver;
/* Streamer */
typedef struct
{
Uint8 *buffer;
int max_len; /* the maximum length in bytes */
int read_pos, write_pos; /* the position of the write and read heads in bytes */
} SDL_AudioStreamer;
/* Define the SDL audio driver structure */
struct SDL_AudioDevice
{
/* * * */
/* Data common to all devices */
/* The current audio specification (shared with audio thread) */
SDL_AudioSpec spec;
/* An audio conversion block for audio format emulation */
SDL_AudioCVT convert;
/* The streamer, if sample rate conversion necessitates it */
int use_streamer;
SDL_AudioStreamer streamer;
/* Current state flags */
int iscapture;
int enabled;
int paused;
int opened;
/* Fake audio buffer for when the audio hardware is busy */
Uint8 *fake_stream;
/* A semaphore for locking the mixing buffers */
SDL_mutex *mixer_lock;
/* A thread to feed the audio device */
SDL_Thread *thread;
SDL_threadID threadid;
/* Queued buffers (if app not using callback). */
SDL_AudioBufferQueue *buffer_queue_head; /* device fed from here. */
SDL_AudioBufferQueue *buffer_queue_tail; /* queue fills to here. */
SDL_AudioBufferQueue *buffer_queue_pool; /* these are unused packets. */
Uint32 queued_bytes; /* number of bytes of audio data in the queue. */
/* * * */
/* Data private to this driver */
struct SDL_PrivateAudioData *hidden;
};
#undef _THIS
typedef struct AudioBootStrap
{
const char *name;
const char *desc;
int (*init) (SDL_AudioDriverImpl * impl);
int demand_only; /* 1==request explicitly, or it won't be available. */
} AudioBootStrap;
#endif /* _SDL_sysaudio_h */
/* vi: set ts=4 sw=4 expandtab: */