src/audio/SDL_sysaudio.h
author Ryan C. Gordon
Tue, 02 Aug 2016 13:50:21 -0400
changeset 10239 04cda108b406
parent 10238 6fa358b97f4b
child 10255 9530fc07da6c
permissions -rw-r--r--
audio: implemented higher level infrastructure for running capture devices.
     1 /*
     2   Simple DirectMedia Layer
     3   Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 #include "../SDL_internal.h"
    22 
    23 #ifndef _SDL_sysaudio_h
    24 #define _SDL_sysaudio_h
    25 
    26 #include "SDL_mutex.h"
    27 #include "SDL_thread.h"
    28 
    29 /* The SDL audio driver */
    30 typedef struct SDL_AudioDevice SDL_AudioDevice;
    31 #define _THIS   SDL_AudioDevice *_this
    32 
    33 /* Audio targets should call this as devices are added to the system (such as
    34    a USB headset being plugged in), and should also be called for
    35    for every device found during DetectDevices(). */
    36 extern void SDL_AddAudioDevice(const int iscapture, const char *name, void *handle);
    37 
    38 /* Audio targets should call this as devices are removed, so SDL can update
    39    its list of available devices. */
    40 extern void SDL_RemoveAudioDevice(const int iscapture, void *handle);
    41 
    42 /* Audio targets should call this if an opened audio device is lost while
    43    being used. This can happen due to i/o errors, or a device being unplugged,
    44    etc. If the device is totally gone, please also call SDL_RemoveAudioDevice()
    45    as appropriate so SDL's list of devices is accurate. */
    46 extern void SDL_OpenedAudioDeviceDisconnected(SDL_AudioDevice *device);
    47 
    48 
    49 /* This is the size of a packet when using SDL_QueueAudio(). We allocate
    50    these as necessary and pool them, under the assumption that we'll
    51    eventually end up with a handful that keep recycling, meeting whatever
    52    the app needs. We keep packing data tightly as more arrives to avoid
    53    wasting space, and if we get a giant block of data, we'll split them
    54    into multiple packets behind the scenes. My expectation is that most
    55    apps will have 2-3 of these in the pool. 8k should cover most needs, but
    56    if this is crippling for some embedded system, we can #ifdef this.
    57    The system preallocates enough packets for 2 callbacks' worth of data. */
    58 #define SDL_AUDIOBUFFERQUEUE_PACKETLEN (8 * 1024)
    59 
    60 /* Used by apps that queue audio instead of using the callback. */
    61 typedef struct SDL_AudioBufferQueue
    62 {
    63     Uint8 data[SDL_AUDIOBUFFERQUEUE_PACKETLEN];  /* packet data. */
    64     Uint32 datalen;  /* bytes currently in use in this packet. */
    65     Uint32 startpos;  /* bytes currently consumed in this packet. */
    66     struct SDL_AudioBufferQueue *next;  /* next item in linked list. */
    67 } SDL_AudioBufferQueue;
    68 
    69 typedef struct SDL_AudioDriverImpl
    70 {
    71     void (*DetectDevices) (void);
    72     int (*OpenDevice) (_THIS, void *handle, const char *devname, int iscapture);
    73     void (*ThreadInit) (_THIS); /* Called by audio thread at start */
    74     void (*WaitDevice) (_THIS);
    75     void (*PlayDevice) (_THIS);
    76     int (*GetPendingBytes) (_THIS);
    77     Uint8 *(*GetDeviceBuf) (_THIS);
    78     void (*WaitDone) (_THIS);
    79     int (*CaptureFromDevice) (_THIS, void *buffer, int buflen);
    80     void (*FlushCapture) (_THIS);
    81     void (*CloseDevice) (_THIS);
    82     void (*LockDevice) (_THIS);
    83     void (*UnlockDevice) (_THIS);
    84     void (*FreeDeviceHandle) (void *handle);  /**< SDL is done with handle from SDL_AddAudioDevice() */
    85     void (*Deinitialize) (void);
    86 
    87     /* !!! FIXME: add pause(), so we can optimize instead of mixing silence. */
    88 
    89     /* Some flags to push duplicate code into the core and reduce #ifdefs. */
    90     /* !!! FIXME: these should be SDL_bool */
    91     int ProvidesOwnCallbackThread;
    92     int SkipMixerLock;  /* !!! FIXME: do we need this anymore? */
    93     int HasCaptureSupport;
    94     int OnlyHasDefaultOutputDevice;
    95     int OnlyHasDefaultInputDevice;
    96     int AllowsArbitraryDeviceNames;
    97 } SDL_AudioDriverImpl;
    98 
    99 
   100 typedef struct SDL_AudioDeviceItem
   101 {
   102     void *handle;
   103     struct SDL_AudioDeviceItem *next;
   104     #if (defined(__GNUC__) && (__GNUC__ <= 2))
   105     char name[1];  /* actually variable length. */
   106     #else
   107     char name[];
   108     #endif
   109 } SDL_AudioDeviceItem;
   110 
   111 
   112 typedef struct SDL_AudioDriver
   113 {
   114     /* * * */
   115     /* The name of this audio driver */
   116     const char *name;
   117 
   118     /* * * */
   119     /* The description of this audio driver */
   120     const char *desc;
   121 
   122     SDL_AudioDriverImpl impl;
   123 
   124     /* A mutex for device detection */
   125     SDL_mutex *detectionLock;
   126     SDL_bool captureDevicesRemoved;
   127     SDL_bool outputDevicesRemoved;
   128     int outputDeviceCount;
   129     int inputDeviceCount;
   130     SDL_AudioDeviceItem *outputDevices;
   131     SDL_AudioDeviceItem *inputDevices;
   132 } SDL_AudioDriver;
   133 
   134 
   135 /* Streamer */
   136 typedef struct
   137 {
   138     Uint8 *buffer;
   139     int max_len;                /* the maximum length in bytes */
   140     int read_pos, write_pos;    /* the position of the write and read heads in bytes */
   141 } SDL_AudioStreamer;
   142 
   143 
   144 /* Define the SDL audio driver structure */
   145 struct SDL_AudioDevice
   146 {
   147     /* * * */
   148     /* Data common to all devices */
   149     SDL_AudioDeviceID id;
   150 
   151     /* The current audio specification (shared with audio thread) */
   152     SDL_AudioSpec spec;
   153 
   154     /* An audio conversion block for audio format emulation */
   155     SDL_AudioCVT convert;
   156 
   157     /* The streamer, if sample rate conversion necessitates it */
   158     int use_streamer;
   159     SDL_AudioStreamer streamer;
   160 
   161     /* Current state flags */
   162     SDL_atomic_t shutdown; /* true if we are signaling the play thread to end. */
   163     SDL_atomic_t enabled;  /* true if device is functioning and connected. */
   164     SDL_atomic_t paused;
   165     SDL_bool opened;
   166     SDL_bool iscapture;
   167 
   168     /* Fake audio buffer for when the audio hardware is busy */
   169     Uint8 *fake_stream;
   170 
   171     /* A mutex for locking the mixing buffers */
   172     SDL_mutex *mixer_lock;
   173 
   174     /* A thread to feed the audio device */
   175     SDL_Thread *thread;
   176     SDL_threadID threadid;
   177 
   178     /* Queued buffers (if app not using callback). */
   179     SDL_AudioBufferQueue *buffer_queue_head; /* device fed from here. */
   180     SDL_AudioBufferQueue *buffer_queue_tail; /* queue fills to here. */
   181     SDL_AudioBufferQueue *buffer_queue_pool; /* these are unused packets. */
   182     Uint32 queued_bytes;  /* number of bytes of audio data in the queue. */
   183 
   184     /* * * */
   185     /* Data private to this driver */
   186     struct SDL_PrivateAudioData *hidden;
   187 };
   188 #undef _THIS
   189 
   190 typedef struct AudioBootStrap
   191 {
   192     const char *name;
   193     const char *desc;
   194     int (*init) (SDL_AudioDriverImpl * impl);
   195     int demand_only;  /* 1==request explicitly, or it won't be available. */
   196 } AudioBootStrap;
   197 
   198 #endif /* _SDL_sysaudio_h */
   199 
   200 /* vi: set ts=4 sw=4 expandtab: */