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Core Audio sine wave example
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| // To run: | |
| // clang core-audio-sine-wave.c -framework AudioUnit && ./a.out | |
| #include <AudioUnit/AudioUnit.h> | |
| #define SAMPLING_RATE 48000 | |
| #define TONE_FREQUENCY 440 | |
| #define M_TAU 2 * M_PI | |
| OSStatus RenderSineWave( | |
| void *inRefCon, | |
| AudioUnitRenderActionFlags *ioActionFlags, | |
| const AudioTimeStamp *inTimeStamp, | |
| UInt32 inBusNumber, | |
| UInt32 inNumberFrames, | |
| AudioBufferList *ioData) | |
| { | |
| static float theta; | |
| float *channel = (float *)ioData->mBuffers[0].mData; | |
| for (UInt32 frame = 0; frame < inNumberFrames; ++frame) { | |
| channel[frame] = sin(theta); | |
| theta += M_TAU * TONE_FREQUENCY / SAMPLING_RATE; | |
| if (theta > M_TAU) { | |
| theta -= M_TAU; | |
| } | |
| } | |
| return noErr; | |
| } | |
| int main() { | |
| OSErr err; | |
| AudioComponentDescription acd; | |
| acd.componentType = kAudioUnitType_Output; | |
| acd.componentSubType = kAudioUnitSubType_DefaultOutput; | |
| acd.componentManufacturer = kAudioUnitManufacturer_Apple; | |
| acd.componentFlags = 0; | |
| acd.componentFlagsMask = 0; | |
| AudioComponent output = AudioComponentFindNext(NULL, &acd); | |
| if (!output) printf("Can't find default output\n"); | |
| AudioUnit toneUnit; | |
| err = AudioComponentInstanceNew(output, &toneUnit); | |
| if (err) fprintf(stderr, "Error creating unit: %d\n", err); | |
| AURenderCallbackStruct input; | |
| input.inputProc = RenderSineWave; | |
| input.inputProcRefCon = NULL; | |
| err = AudioUnitSetProperty(toneUnit, kAudioUnitProperty_SetRenderCallback, | |
| kAudioUnitScope_Input, 0, &input, sizeof(input)); | |
| if (err) printf("Error setting callback: %d\n", err); | |
| AudioStreamBasicDescription asbd; | |
| asbd.mFormatID = kAudioFormatLinearPCM; | |
| asbd.mFormatFlags = kAudioFormatFlagsNativeFloatPacked; | |
| asbd.mSampleRate = SAMPLING_RATE; | |
| asbd.mBitsPerChannel = 32; | |
| asbd.mChannelsPerFrame = 1; | |
| asbd.mFramesPerPacket = 1; | |
| asbd.mBytesPerFrame = asbd.mBitsPerChannel / 8 * asbd.mChannelsPerFrame; | |
| asbd.mBytesPerPacket = asbd.mBytesPerFrame * asbd.mFramesPerPacket; | |
| err = AudioUnitSetProperty(toneUnit, kAudioUnitProperty_StreamFormat, | |
| kAudioUnitScope_Input, 0, &asbd, sizeof(asbd)); | |
| if (err) printf("Error setting stream format: %d\n", err); | |
| err = AudioUnitInitialize(toneUnit); | |
| if (err) printf("Error initializing unit: %d\n", err); | |
| err = AudioOutputUnitStart(toneUnit); | |
| if (err) printf("Error starting unit: %d\n", err); | |
| usleep(2000000); | |
| AudioOutputUnitStop(toneUnit); | |
| AudioUnitUninitialize(toneUnit); | |
| AudioComponentInstanceDispose(toneUnit); | |
| } |
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