/* * OpenAL Loopback Example * * Copyright (c) 2013 by Chris Robinson <chris.kcat@gmail.com> * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ /* This file contains an example for using the loopback device for custom * output handling. */ #include <stdio.h> #include <assert.h> #include <math.h> #include <SDL.h> #include "AL/al.h" #include "AL/alc.h" #include "AL/alext.h" #include "common/alhelpers.h" #ifndef M_PI #define M_PI (3.14159265358979323846) #endif typedef struct { ALCdevice *Device; ALCcontext *Context; ALCsizei FrameSize; } PlaybackInfo; static LPALCLOOPBACKOPENDEVICESOFT alcLoopbackOpenDeviceSOFT; static LPALCISRENDERFORMATSUPPORTEDSOFT alcIsRenderFormatSupportedSOFT; static LPALCRENDERSAMPLESSOFT alcRenderSamplesSOFT; void SDLCALL RenderSDLSamples(void *userdata, Uint8 *stream, int len) { PlaybackInfo *playback = (PlaybackInfo*)userdata; alcRenderSamplesSOFT(playback->Device, stream, len/playback->FrameSize); } /* Creates a one second buffer containing a sine wave, and returns the new * buffer ID. */ static ALuint CreateSineWave(void) { ALshort data[44100]; ALuint buffer; ALenum err; ALuint i; for(i = 0;i < 44100;i++) data[i] = (ALshort)(sin(i * 441.0 / 44100.0 * 2.0*M_PI)*32767.0); /* Buffer the audio data into a new buffer object. */ buffer = 0; alGenBuffers(1, &buffer); alBufferData(buffer, AL_FORMAT_MONO16, data, sizeof(data), 44100); /* Check if an error occured, and clean up if so. */ err = alGetError(); if(err != AL_NO_ERROR) { fprintf(stderr, "OpenAL Error: %s\n", alGetString(err)); if(alIsBuffer(buffer)) alDeleteBuffers(1, &buffer); return 0; } return buffer; } int main() { PlaybackInfo playback = { NULL, NULL, 0 }; SDL_AudioSpec desired, obtained; ALuint source, buffer; ALCint attrs[16]; ALenum state; /* Print out error if extension is missing. */ if(!alcIsExtensionPresent(NULL, "ALC_SOFT_loopback")) { fprintf(stderr, "Error: ALC_SOFT_loopback not supported!\n"); return 1; } /* Define a macro to help load the function pointers. */ #define LOAD_PROC(x) ((x) = alcGetProcAddress(NULL, #x)) LOAD_PROC(alcLoopbackOpenDeviceSOFT); LOAD_PROC(alcIsRenderFormatSupportedSOFT); LOAD_PROC(alcRenderSamplesSOFT); #undef LOAD_PROC if(SDL_Init(SDL_INIT_AUDIO) == -1) { fprintf(stderr, "Failed to init SDL audio: %s\n", SDL_GetError()); return 1; } /* Set up SDL audio with our requested format and callback. */ desired.channels = 2; desired.format = AUDIO_S16SYS; desired.freq = 44100; desired.padding = 0; desired.samples = 4096; desired.callback = RenderSDLSamples; desired.userdata = &playback; if(SDL_OpenAudio(&desired, &obtained) != 0) { SDL_Quit(); fprintf(stderr, "Failed to open SDL audio: %s\n", SDL_GetError()); return 1; } /* Set up our OpenAL attributes based on what we got from SDL. */ attrs[0] = ALC_FORMAT_CHANNELS_SOFT; if(obtained.channels == 1) attrs[1] = ALC_MONO_SOFT; else if(obtained.channels == 2) attrs[1] = ALC_STEREO_SOFT; else { fprintf(stderr, "Unhandled SDL channel count: %d\n", obtained.channels); goto error; } attrs[2] = ALC_FORMAT_TYPE_SOFT; if(obtained.format == AUDIO_U8) attrs[3] = ALC_UNSIGNED_BYTE_SOFT; else if(obtained.format == AUDIO_S8) attrs[3] = ALC_BYTE_SOFT; else if(obtained.format == AUDIO_U16SYS) attrs[3] = ALC_UNSIGNED_SHORT_SOFT; else if(obtained.format == AUDIO_S16SYS) attrs[3] = ALC_SHORT_SOFT; else { fprintf(stderr, "Unhandled SDL format: 0x%04x\n", obtained.format); goto error; } attrs[4] = ALC_FREQUENCY; attrs[5] = obtained.freq; attrs[6] = 0; /* end of list */ /* Initialize OpenAL loopback device, using our format attributes. */ playback.Device = alcLoopbackOpenDeviceSOFT(NULL); if(!playback.Device) { fprintf(stderr, "Failed to open loopback device!\n"); goto error; } /* Make sure the format is supported before setting them on the device. */ if(alcIsRenderFormatSupportedSOFT(playback.Device, attrs[5], attrs[1], attrs[3]) == ALC_FALSE) { fprintf(stderr, "Render format not supported: %s, %s, %dhz\n", ChannelsName(attrs[1]), TypeName(attrs[3]), attrs[5]); goto error; } playback.Context = alcCreateContext(playback.Device, attrs); if(!playback.Context || alcMakeContextCurrent(playback.Context) == ALC_FALSE) { fprintf(stderr, "Failed to set an OpenAL audio context\n"); goto error; } playback.FrameSize = FramesToBytes(1, attrs[1], attrs[3]); /* Start SDL playing. Our callback (thus alcRenderSamplesSOFT) will now * start being called regularly to update the AL playback state. */ SDL_PauseAudio(0); /* Load the sound into a buffer. */ buffer = CreateSineWave(); if(!buffer) { SDL_CloseAudio(); alcDestroyContext(playback.Context); alcCloseDevice(playback.Device); SDL_Quit(); return 1; } /* Create the source to play the sound with. */ source = 0; alGenSources(1, &source); alSourcei(source, AL_BUFFER, buffer); assert(alGetError()==AL_NO_ERROR && "Failed to setup sound source"); /* Play the sound until it finishes. */ alSourcePlay(source); do { Sleep(10); alGetSourcei(source, AL_SOURCE_STATE, &state); } while(alGetError() == AL_NO_ERROR && state == AL_PLAYING); /* All done. Delete resources, and close OpenAL. */ alDeleteSources(1, &source); alDeleteBuffers(1, &buffer); /* Stop SDL playing. */ SDL_PauseAudio(1); /* Close up OpenAL and SDL. */ SDL_CloseAudio(); alcDestroyContext(playback.Context); alcCloseDevice(playback.Device); SDL_Quit(); return 0; error: SDL_CloseAudio(); if(playback.Context) alcDestroyContext(playback.Context); if(playback.Device) alcCloseDevice(playback.Device); SDL_Quit(); return 1; }