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 M_PI
  42 #define M_PI    (3.14159265358979323846)
  43 #endif
  44
  45 typedef struct {
  46     ALCdevice *Device;
  47     ALCcontext *Context;
  48
  49     ALCsizei FrameSize;
  50 } PlaybackInfo;
  51
  52 static LPALCLOOPBACKOPENDEVICESOFT alcLoopbackOpenDeviceSOFT;
  53 static LPALCISRENDERFORMATSUPPORTEDSOFT alcIsRenderFormatSupportedSOFT;
  54 static LPALCRENDERSAMPLESSOFT alcRenderSamplesSOFT;
  55
  56
  57 void SDLCALL RenderSDLSamples(void *userdata, Uint8 *stream, int len)
  58 {
  59     PlaybackInfo *playback = (PlaybackInfo*)userdata;
  60     alcRenderSamplesSOFT(playback->Device, stream, len/playback->FrameSize);
  61 }
  62
  63
  64 static const char *ChannelsName(ALCenum chans)
  65 {
  66     switch(chans)
  67     {
  68     case ALC_MONO_SOFT: return "Mono";
  69     case ALC_STEREO_SOFT: return "Stereo";
  70     case ALC_QUAD_SOFT: return "Quadraphonic";
  71     case ALC_5POINT1_SOFT: return "5.1 Surround";
  72     case ALC_6POINT1_SOFT: return "6.1 Surround";
  73     case ALC_7POINT1_SOFT: return "7.1 Surround";
  74     }
  75     return "Unknown Channels";
  76 }
  77
  78 static const char *TypeName(ALCenum type)
  79 {
  80     switch(type)
  81     {
  82     case ALC_BYTE_SOFT: return "S8";
  83     case ALC_UNSIGNED_BYTE_SOFT: return "U8";
  84     case ALC_SHORT_SOFT: return "S16";
  85     case ALC_UNSIGNED_SHORT_SOFT: return "U16";
  86     case ALC_INT_SOFT: return "S32";
  87     case ALC_UNSIGNED_INT_SOFT: return "U32";
  88     case ALC_FLOAT_SOFT: return "Float32";
  89     }
  90     return "Unknown Type";
  91 }
  92
  93 /* Creates a one second buffer containing a sine wave, and returns the new
  94  * buffer ID. */
  95 static ALuint CreateSineWave(void)
  96 {
  97     ALshort data[44100*4];
  98     ALuint buffer;
  99     ALenum err;
 100     ALuint i;
 101
 102     for(i = 0;i < 44100*4;i++)
 103         data[i] = (ALshort)(sin(i/44100.0 * 1000.0 * 2.0*M_PI) * 32767.0);
 104
 105     /* Buffer the audio data into a new buffer object. */
 106     buffer = 0;
 107     alGenBuffers(1, &buffer);
 108     alBufferData(buffer, AL_FORMAT_MONO16, data, sizeof(data), 44100);
 109
 110     /* Check if an error occured, and clean up if so. */
 111     err = alGetError();
 112     if(err != AL_NO_ERROR)
 113     {
 114         fprintf(stderr, "OpenAL Error: %s\n", alGetString(err));
 115         if(alIsBuffer(buffer))
 116             alDeleteBuffers(1, &buffer);
 117         return 0;
 118     }
 119
 120     return buffer;
 121 }
 122
 123
 124 int main(int argc, char *argv[])
 125 {
 126     PlaybackInfo playback = { NULL, NULL, 0 };
 127     SDL_AudioSpec desired, obtained;
 128     ALuint source, buffer;
 129     ALCint attrs[16];
 130     ALenum state;
 131     (void)argc;
 132     (void)argv;
 133
 134     /* Print out error if extension is missing. */
 135     if(!alcIsExtensionPresent(NULL, "ALC_SOFT_loopback"))
 136     {
 137         fprintf(stderr, "Error: ALC_SOFT_loopback not supported!\n");
 138         return 1;
 139     }
 140
 141     /* Define a macro to help load the function pointers. */
 142 #define LOAD_PROC(x)  ((x) = alcGetProcAddress(NULL, #x))
 143     LOAD_PROC(alcLoopbackOpenDeviceSOFT);
 144     LOAD_PROC(alcIsRenderFormatSupportedSOFT);
 145     LOAD_PROC(alcRenderSamplesSOFT);
 146 #undef LOAD_PROC
 147
 148     if(SDL_Init(SDL_INIT_AUDIO) == -1)
 149     {
 150         fprintf(stderr, "Failed to init SDL audio: %s\n", SDL_GetError());
 151         return 1;
 152     }
 153
 154     /* Set up SDL audio with our requested format and callback. */
 155     desired.channels = 2;
 156     desired.format = AUDIO_S16SYS;
 157     desired.freq = 44100;
 158     desired.padding = 0;
 159     desired.samples = 4096;
 160     desired.callback = RenderSDLSamples;
 161     desired.userdata = &playback;
 162     if(SDL_OpenAudio(&desired, &obtained) != 0)
 163     {
 164         SDL_Quit();
 165         fprintf(stderr, "Failed to open SDL audio: %s\n", SDL_GetError());
 166         return 1;
 167     }
 168
 169     /* Set up our OpenAL attributes based on what we got from SDL. */
 170     attrs[0] = ALC_FORMAT_CHANNELS_SOFT;
 171     if(obtained.channels == 1)
 172         attrs[1] = ALC_MONO_SOFT;
 173     else if(obtained.channels == 2)
 174         attrs[1] = ALC_STEREO_SOFT;
 175     else
 176     {
 177         fprintf(stderr, "Unhandled SDL channel count: %d\n", obtained.channels);
 178         goto error;
 179     }
 180
 181     attrs[2] = ALC_FORMAT_TYPE_SOFT;
 182     if(obtained.format == AUDIO_U8)
 183         attrs[3] = ALC_UNSIGNED_BYTE_SOFT;
 184     else if(obtained.format == AUDIO_S8)
 185         attrs[3] = ALC_BYTE_SOFT;
 186     else if(obtained.format == AUDIO_U16SYS)
 187         attrs[3] = ALC_UNSIGNED_SHORT_SOFT;
 188     else if(obtained.format == AUDIO_S16SYS)
 189         attrs[3] = ALC_SHORT_SOFT;
 190     else
 191     {
 192         fprintf(stderr, "Unhandled SDL format: 0x%04x\n", obtained.format);
 193         goto error;
 194     }
 195
 196     attrs[4] = ALC_FREQUENCY;
 197     attrs[5] = obtained.freq;
 198
 199     attrs[6] = 0; /* end of list */
 200
 201     playback.FrameSize = obtained.channels * SDL_AUDIO_BITSIZE(obtained.format) / 8;
 202
 203     /* Initialize OpenAL loopback device, using our format attributes. */
 204     playback.Device = alcLoopbackOpenDeviceSOFT(NULL);
 205     if(!playback.Device)
 206     {
 207         fprintf(stderr, "Failed to open loopback device!\n");
 208         goto error;
 209     }
 210     /* Make sure the format is supported before setting them on the device. */
 211     if(alcIsRenderFormatSupportedSOFT(playback.Device, attrs[5], attrs[1], attrs[3]) == ALC_FALSE)
 212     {
 213         fprintf(stderr, "Render format not supported: %s, %s, %dhz\n",
 214                         ChannelsName(attrs[1]), TypeName(attrs[3]), attrs[5]);
 215         goto error;
 216     }
 217     playback.Context = alcCreateContext(playback.Device, attrs);
 218     if(!playback.Context || alcMakeContextCurrent(playback.Context) == ALC_FALSE)
 219     {
 220         fprintf(stderr, "Failed to set an OpenAL audio context\n");
 221         goto error;
 222     }
 223
 224     /* Start SDL playing. Our callback (thus alcRenderSamplesSOFT) will now
 225      * start being called regularly to update the AL playback state. */
 226     SDL_PauseAudio(0);
 227
 228     /* Load the sound into a buffer. */
 229     buffer = CreateSineWave();
 230     if(!buffer)
 231     {
 232         SDL_CloseAudio();
 233         alcDestroyContext(playback.Context);
 234         alcCloseDevice(playback.Device);
 235         SDL_Quit();
 236         return 1;
 237     }
 238
 239     /* Create the source to play the sound with. */
 240     source = 0;
 241     alGenSources(1, &source);
 242     alSourcei(source, AL_BUFFER, buffer);
 243     assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source");
 244
 245     /* Play the sound until it finishes. */
 246     alSourcePlay(source);
 247     do {
 248         al_nssleep(10000000);
 249         alGetSourcei(source, AL_SOURCE_STATE, &state);
 250     } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING);
 251
 252     /* All done. Delete resources, and close OpenAL. */
 253     alDeleteSources(1, &source);
 254     alDeleteBuffers(1, &buffer);
 255
 256     /* Stop SDL playing. */
 257     SDL_PauseAudio(1);
 258
 259     /* Close up OpenAL and SDL. */
 260     SDL_CloseAudio();
 261     alcDestroyContext(playback.Context);
 262     alcCloseDevice(playback.Device);
 263     SDL_Quit();
 264
 265     return 0;
 266
 267 error:
 268     SDL_CloseAudio();
 269     if(playback.Context)
 270         alcDestroyContext(playback.Context);
 271     if(playback.Device)
 272         alcCloseDevice(playback.Device);
 273     SDL_Quit();
 274
 275     return 1;
 276 }