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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 SAMPLE_RATE 48000 | |
| #define TONE_FREQUENCY 440 | |
| #define M_TAU 2.0 * M_PI | |
| OSStatus RenderSineWave( | |
| void *inRefCon, | |
| AudioUnitRenderActionFlags *ioActionFlags, | |
| const AudioTimeStamp *inTimeStamp, | |
| UInt32 inBusNumber, | |
| UInt32 inNumberFrames, | |
| AudioBufferList *ioData) | |
| { | |
| static float theta; | |
| float *left = (float *)ioData->mBuffers[0].mData; | |
| for (UInt32 frame = 0; frame < inNumberFrames; ++frame) { | |
| left[frame] = sin(theta); | |
| theta += M_TAU * TONE_FREQUENCY / SAMPLE_RATE; | |
| if (theta > M_TAU) { | |
| theta -= M_TAU; | |
| } | |
| } | |
| // Copy left channel to right channel | |
| memcpy(ioData->mBuffers[1].mData, left, ioData->mBuffers[1].mDataByteSize); | |
| return noErr; | |
| } | |
| int main() { | |
| OSErr err; | |
| AudioComponentDescription acd = { | |
| .componentType = kAudioUnitType_Output, | |
| .componentSubType = kAudioUnitSubType_DefaultOutput, | |
| .componentManufacturer = kAudioUnitManufacturer_Apple, | |
| }; | |
| 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 = {0}; | |
| input.inputProc = RenderSineWave; | |
| err = AudioUnitSetProperty(toneUnit, kAudioUnitProperty_SetRenderCallback, | |
| kAudioUnitScope_Input, 0, &input, sizeof(input)); | |
| if (err) printf("Error setting callback: %d\n", err); | |
| AudioStreamBasicDescription asbd = { | |
| .mFormatID = kAudioFormatLinearPCM, | |
| .mFormatFlags = 0 | |
| | kAudioFormatFlagsNativeFloatPacked | |
| | kAudioFormatFlagIsNonInterleaved, | |
| .mSampleRate = 48000, | |
| .mBitsPerChannel = 32, | |
| .mChannelsPerFrame = 2, | |
| .mFramesPerPacket = 1, | |
| .mBytesPerFrame = 4, | |
| .mBytesPerPacket = 4, | |
| }; | |
| 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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