examples/alloopback.c

   1 /*
   2  * OpenAL Loopback Example
   3  *
   4  * Copyright (c) 2013 by Chris Robinson <chris.kcat@gmail.com>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a copy
   7  * of this software and associated documentation files (the "Software"), to deal
   8  * in the Software without restriction, including without limitation the rights
   9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10  * copies of the Software, and to permit persons to whom the Software is
  11  * furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice shall be included in
  14  * all copies or substantial portions of the Software.
  15  *
  16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  22  * THE SOFTWARE.
  23  */
  24
  25 /* This file contains an example for using the loopback device for custom
  26  * output handling.
  27  */
  28
  29 #include <stdio.h>
  30 #include <assert.h>
  31 #include <math.h>
  32
  33 #include <SDL.h>
  34
  35 #include "AL/al.h"
  36 #include "AL/alc.h"
  37 #include "AL/alext.h"
  38
  39 #include "common/alhelpers.h"
  40
  41 #ifndef SDL_AUDIO_MASK_BITSIZE
  42 #define SDL_AUDIO_MASK_BITSIZE (0xFF)
  43 #endif
  44 #ifndef SDL_AUDIO_BITSIZE
  45 #define SDL_AUDIO_BITSIZE(x) (x & SDL_AUDIO_MASK_BITSIZE)
  46 #endif
  47
  48 #ifndef M_PI
  49 #define M_PI    (3.14159265358979323846)
  50 #endif
  51
  52 typedef struct {
  53     ALCdevice *Device;
  54     ALCcontext *Context;
  55
  56     ALCsizei FrameSize;
  57 } PlaybackInfo;
  58
  59 static LPALCLOOPBACKOPENDEVICESOFT alcLoopbackOpenDeviceSOFT;
  60 static LPALCISRENDERFORMATSUPPORTEDSOFT alcIsRenderFormatSupportedSOFT;
  61 static LPALCRENDERSAMPLESSOFT alcRenderSamplesSOFT;
  62
  63
  64 void SDLCALL RenderSDLSamples(void *userdata, Uint8 *stream, int len)
  65 {
  66     PlaybackInfo *playback = (PlaybackInfo*)userdata;
  67     alcRenderSamplesSOFT(playback->Device, stream, len/playback->FrameSize);
  68 }
  69
  70
  71 static const char *ChannelsName(ALCenum chans)
  72 {
  73     switch(chans)
  74     {
  75     case ALC_MONO_SOFT: return "Mono";
  76     case ALC_STEREO_SOFT: return "Stereo";
  77     case ALC_QUAD_SOFT: return "Quadraphonic";
  78     case ALC_5POINT1_SOFT: return "5.1 Surround";
  79     case ALC_6POINT1_SOFT: return "6.1 Surround";
  80     case ALC_7POINT1_SOFT: return "7.1 Surround";
  81     }
  82     return "Unknown Channels";
  83 }
  84
  85 static const char *TypeName(ALCenum type)
  86 {
  87     switch(type)
  88     {
  89     case ALC_BYTE_SOFT: return "S8";
  90     case ALC_UNSIGNED_BYTE_SOFT: return "U8";
  91     case ALC_SHORT_SOFT: return "S16";
  92     case ALC_UNSIGNED_SHORT_SOFT: return "U16";
  93     case ALC_INT_SOFT: return "S32";
  94     case ALC_UNSIGNED_INT_SOFT: return "U32";
  95     case ALC_FLOAT_SOFT: return "Float32";
  96     }
  97     return "Unknown Type";
  98 }
  99
 100 /* Creates a one second buffer containing a sine wave, and returns the new
 101  * buffer ID. */
 102 static ALuint CreateSineWave(void)
 103 {
 104     ALshort data[44100*4];
 105     ALuint buffer;
 106     ALenum err;
 107     ALuint i;
 108
 109     for(i = 0;i < 44100*4;i++)
 110         data[i] = (ALshort)(sin(i/44100.0 * 1000.0 * 2.0*M_PI) * 32767.0);
 111
 112     /* Buffer the audio data into a new buffer object. */
 113     buffer = 0;
 114     alGenBuffers(1, &buffer);
 115     alBufferData(buffer, AL_FORMAT_MONO16, data, sizeof(data), 44100);
 116
 117     /* Check if an error occured, and clean up if so. */
 118     err = alGetError();
 119     if(err != AL_NO_ERROR)
 120     {
 121         fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));
 122         if(alIsBuffer(buffer))
 123             alDeleteBuffers(1, &buffer);
 124         return 0;
 125     }
 126
 127     return buffer;
 128 }
 129
 130
 131 int main(int argc, char *argv[])
 132 {
 133     PlaybackInfo playback = { NULL, NULL, 0 };
 134     SDL_AudioSpec desired, obtained;
 135     ALuint source, buffer;
 136     ALCint attrs[16];
 137     ALenum state;
 138     (void)argc;
 139     (void)argv;
 140
 141     /* Print out error if extension is missing. */
 142     if(!alcIsExtensionPresent(NULL, "ALC_SOFT_loopback"))
 143     {
 144         fprintf(stderr, "Error: ALC_SOFT_loopback not supported!\n");
 145         return 1;
 146     }
 147
 148     /* Define a macro to help load the function pointers. */
 149 #define LOAD_PROC(x)  ((x) = alcGetProcAddress(NULL, #x))
 150     LOAD_PROC(alcLoopbackOpenDeviceSOFT);
 151     LOAD_PROC(alcIsRenderFormatSupportedSOFT);
 152     LOAD_PROC(alcRenderSamplesSOFT);
 153 #undef LOAD_PROC
 154
 155     if(SDL_Init(SDL_INIT_AUDIO) == -1)
 156     {
 157         fprintf(stderr, "Failed to init SDL audio: %s\n", SDL_GetError());
 158         return 1;
 159     }
 160
 161     /* Set up SDL audio with our requested format and callback. */
 162     desired.channels = 2;
 163     desired.format = AUDIO_S16SYS;
 164     desired.freq = 44100;
 165     desired.padding = 0;
 166     desired.samples = 4096;
 167     desired.callback = RenderSDLSamples;
 168     desired.userdata = &playback;
 169     if(SDL_OpenAudio(&desired, &obtained) != 0)
 170     {
 171         SDL_Quit();
 172         fprintf(stderr, "Failed to open SDL audio: %s\n", SDL_GetError());
 173         return 1;
 174     }
 175
 176     /* Set up our OpenAL attributes based on what we got from SDL. */
 177     attrs[0] = ALC_FORMAT_CHANNELS_SOFT;
 178     if(obtained.channels == 1)
 179         attrs[1] = ALC_MONO_SOFT;
 180     else if(obtained.channels == 2)
 181         attrs[1] = ALC_STEREO_SOFT;
 182     else
 183     {
 184         fprintf(stderr, "Unhandled SDL channel count: %d\n", obtained.channels);
 185         goto error;
 186     }
 187
 188     attrs[2] = ALC_FORMAT_TYPE_SOFT;
 189     if(obtained.format == AUDIO_U8)
 190         attrs[3] = ALC_UNSIGNED_BYTE_SOFT;
 191     else if(obtained.format == AUDIO_S8)
 192         attrs[3] = ALC_BYTE_SOFT;
 193     else if(obtained.format == AUDIO_U16SYS)
 194         attrs[3] = ALC_UNSIGNED_SHORT_SOFT;
 195     else if(obtained.format == AUDIO_S16SYS)
 196         attrs[3] = ALC_SHORT_SOFT;
 197     else
 198     {
 199         fprintf(stderr, "Unhandled SDL format: 0x%04x\n", obtained.format);
 200         goto error;
 201     }
 202
 203     attrs[4] = ALC_FREQUENCY;
 204     attrs[5] = obtained.freq;
 205
 206     attrs[6] = 0; /* end of list */
 207
 208     playback.FrameSize = obtained.channels * SDL_AUDIO_BITSIZE(obtained.format) / 8;
 209
 210     /* Initialize OpenAL loopback device, using our format attributes. */
 211     playback.Device = alcLoopbackOpenDeviceSOFT(NULL);
 212     if(!playback.Device)
 213     {
 214         fprintf(stderr, "Failed to open loopback device!\n");
 215         goto error;
 216     }
 217     /* Make sure the format is supported before setting them on the device. */
 218     if(alcIsRenderFormatSupportedSOFT(playback.Device, attrs[5], attrs[1], attrs[3]) == ALC_FALSE)
 219     {
 220         fprintf(stderr, "Render format not supported: %s, %s, %dhz\n",
 221                         ChannelsName(attrs[1]), TypeName(attrs[3]), attrs[5]);
 222         goto error;
 223     }
 224     playback.Context = alcCreateContext(playback.Device, attrs);
 225     if(!playback.Context || alcMakeContextCurrent(playback.Context) == ALC_FALSE)
 226     {
 227         fprintf(stderr, "Failed to set an OpenAL audio context\n");
 228         goto error;
 229     }
 230
 231     /* Start SDL playing. Our callback (thus alcRenderSamplesSOFT) will now
 232      * start being called regularly to update the AL playback state. */
 233     SDL_PauseAudio(0);
 234
 235     /* Load the sound into a buffer. */
 236     buffer = CreateSineWave();
 237     if(!buffer)
 238     {
 239         SDL_CloseAudio();
 240         alcDestroyContext(playback.Context);
 241         alcCloseDevice(playback.Device);
 242         SDL_Quit();
 243         return 1;
 244     }
 245
 246     /* Create the source to play the sound with. */
 247     source = 0;
 248     alGenSources(1, &source);
 249     alSourcei(source, AL_BUFFER, buffer);
 250     assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
 251
 252     /* Play the sound until it finishes. */
 253     alSourcePlay(source);
 254     do {
 255         al_nssleep(10000000);
 256         alGetSourcei(source, AL_SOURCE_STATE, &state);
 257     } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING);
 258
 259     /* All done. Delete resources, and close OpenAL. */
 260     alDeleteSources(1, &source);
 261     alDeleteBuffers(1, &buffer);
 262
 263     /* Stop SDL playing. */
 264     SDL_PauseAudio(1);
 265
 266     /* Close up OpenAL and SDL. */
 267     SDL_CloseAudio();
 268     alcDestroyContext(playback.Context);
 269     alcCloseDevice(playback.Device);
 270     SDL_Quit();
 271
 272     return 0;
 273
 274 error:
 275     SDL_CloseAudio();
 276     if(playback.Context)
 277         alcDestroyContext(playback.Context);
 278     if(playback.Device)
 279         alcCloseDevice(playback.Device);
 280     SDL_Quit();
 281
 282     return 1;
 283 }