我现在正在乱用一个简单的应用程序而且我一直在使用this post by Kevin Murphy中描述的两个类
我的代码工作得很好，只是它拾取了很多背景噪音 - 我只对从吉他上拾取响亮的附近声音感兴趣。
我基本上没有使用Accelerate框架或任何AudioUnit的经验。
任何人都可以通过Kevin Murphy了解这些课程并告诉我如何修改它们以忽略低于某个分贝阈值的声音？
/*
Copyright (c) Kevin P Murphy June 2012
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.
*/
#import "AudioController.h"
#define kOutputBus 0
#define kInputBus 1
@implementation AudioController
@synthesize rioUnit, audioFormat, delegate;
void checkStatus(OSStatus status);
void checkStatus(OSStatus status) {
if(status!=0)
printf("Error: %ld\n", status);
}
#pragma mark init
- (id)init
{
OSStatus status;
status = AudioSessionInitialize(NULL, NULL, NULL, (__bridge void*) self);
checkStatus(status);
// Describe audio component
AudioComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_RemoteIO;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
// Get component
AudioComponent inputComponent = AudioComponentFindNext(NULL, &desc);
// Get audio units
status = AudioComponentInstanceNew(inputComponent, &rioUnit);
checkStatus(status);
// Enable IO for recording
UInt32 flag = 1;
status = AudioUnitSetProperty(rioUnit,
kAudioOutputUnitProperty_EnableIO,
kAudioUnitScope_Input,
kInputBus,
&flag,
sizeof(flag));
checkStatus(status);
// Describe format
audioFormat.mSampleRate= 44100.0;
audioFormat.mFormatID= kAudioFormatLinearPCM;
audioFormat.mFormatFlags= kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket= 1;
audioFormat.mChannelsPerFrame= 1;
audioFormat.mBitsPerChannel= 16;
audioFormat.mBytesPerPacket= 2;
audioFormat.mBytesPerFrame= 2;
// Apply format
status = AudioUnitSetProperty(rioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output,
kInputBus,
&audioFormat,
sizeof(audioFormat));
checkStatus(status);
status = AudioUnitSetProperty(rioUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
kOutputBus,
&audioFormat,
sizeof(audioFormat));
checkStatus(status);
// Set input callback
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = recordingCallback;
callbackStruct.inputProcRefCon = (__bridge void*)self;
status = AudioUnitSetProperty(rioUnit,
kAudioOutputUnitProperty_SetInputCallback,
kAudioUnitScope_Global,
kInputBus,
&callbackStruct,
sizeof(callbackStruct));
checkStatus(status);
// Disable buffer allocation for the recorder
flag = 0;
status = AudioUnitSetProperty(rioUnit, kAudioUnitProperty_ShouldAllocateBuffer, kAudioUnitScope_Global, kInputBus, &flag, sizeof(flag));
// Initialise
UInt32 category = kAudioSessionCategory_PlayAndRecord;
status = AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);
checkStatus(status);
status = 0;
status = AudioSessionSetActive(YES);
checkStatus(status);
status = AudioUnitInitialize(rioUnit);
checkStatus(status);
return self;
}
#pragma mark Recording Callback
static OSStatus recordingCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
AudioController *THIS = (__bridge AudioController*) inRefCon;
THIS->bufferList.mNumberBuffers = 1;
THIS->bufferList.mBuffers[0].mDataByteSize = sizeof(SInt16)*inNumberFrames;
THIS->bufferList.mBuffers[0].mNumberChannels = 1;
THIS->bufferList.mBuffers[0].mData = (SInt16*) malloc(sizeof(SInt16)*inNumberFrames);
OSStatus status;
status = AudioUnitRender(THIS->rioUnit,
ioActionFlags,
inTimeStamp,
inBusNumber,
inNumberFrames,
&(THIS->bufferList));
checkStatus(status);
dispatch_async(dispatch_get_main_queue(), ^{
[THIS.delegate receivedAudioSamples:(SInt16*)THIS->bufferList.mBuffers[0].mData length:inNumberFrames];
});
return noErr;
}
-(void) startAudio
{
OSStatus status = AudioOutputUnitStart(rioUnit);
checkStatus(status);
printf("Audio Initialized - sampleRate: %f\n", audioFormat.mSampleRate);
}
-(void) stopAudio
{
OSStatus status = AudioSessionSetActive(NO);
checkStatus(status);
}
@end
/*
Copyright (c) Kevin P Murphy June 2012
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.
*/
#import "PitchDetector.h"
#import <Accelerate/Accelerate.h>
@implementation PitchDetector
@synthesize lowBoundFrequency, hiBoundFrequency, sampleRate, delegate, running;
#pragma mark Initialize Methods
-(id) initWithSampleRate: (float) rate andDelegate: (id<PitchDetectorDelegate>) initDelegate {
return [self initWithSampleRate:rate lowBoundFreq:40 hiBoundFreq:4500 andDelegate:initDelegate];
}
-(id) initWithSampleRate: (float) rate lowBoundFreq: (int) low hiBoundFreq: (int) hi andDelegate: (id<PitchDetectorDelegate>) initDelegate {
self.lowBoundFrequency = low;
self.hiBoundFrequency = hi;
self.sampleRate = rate;
self.delegate = initDelegate;
bufferLength = self.sampleRate/self.lowBoundFrequency;
hann = (float*) malloc(sizeof(float)*bufferLength);
vDSP_hann_window(hann, bufferLength, vDSP_HANN_NORM);
sampleBuffer = (SInt16*) malloc(512);
samplesInSampleBuffer = 0;
result = (float*) malloc(sizeof(float)*bufferLength);
return self;
}
#pragma mark Insert Samples
- (void) addSamples:(SInt16 *)samples inNumberFrames:(int)frames {
int newLength = frames;
if(samplesInSampleBuffer>0) {
newLength += samplesInSampleBuffer;
}
SInt16 *newBuffer = (SInt16*) malloc(sizeof(SInt16)*newLength);
memcpy(newBuffer, sampleBuffer, samplesInSampleBuffer*sizeof(SInt16));
memcpy(&newBuffer[samplesInSampleBuffer], samples, frames*sizeof(SInt16));
free(sampleBuffer);
sampleBuffer = newBuffer;
samplesInSampleBuffer = newLength;
if(samplesInSampleBuffer>(self.sampleRate/self.lowBoundFrequency)) {
if(!self.running) {
[self performSelectorInBackground:@selector(performWithNumFrames:) withObject:[NSNumber numberWithInt:newLength]];
self.running = YES;
}
samplesInSampleBuffer = 0;
} else {
//printf("NOT ENOUGH SAMPLES: %d\n", newLength);
}
}
#pragma mark Perform Auto Correlation
-(void) performWithNumFrames: (NSNumber*) numFrames;
{
int n = numFrames.intValue;
float freq = 0;
SInt16 *samples = sampleBuffer;
int returnIndex = 0;
float sum;
bool goingUp = false;
float normalize = 0;
for(int i = 0; i<n; i++) {
sum = 0;
for(int j = 0; j<n; j++) {
sum += (samples[j]*samples[j+i])*hann[j];
}
if(i ==0 ) normalize = sum;
result[i] = sum/normalize;
}
for(int i = 0; i<n-8; i++) {
if(result[i]<0) {
i+=2; // no peaks below 0, skip forward at a faster rate
} else {
if(result[i]>result[i-1] && goingUp == false && i >1) {
//local min at i-1
goingUp = true;
} else if(goingUp == true && result[i]<result[i-1]) {
//local max at i-1
if(returnIndex==0 && result[i-1]>result[0]*0.95) {
returnIndex = i-1;
break;
//############### NOTE ##################################
// My implemenation breaks out of this loop when it finds the first peak.
// This is (probably) the greatest source of error, so if you would like to
// improve this algorithm, start here. the next else if() will trigger on
// future local maxima (if you first take out the break; above this paragraph)
//#######################################################
} else if(result[i-1]>result[0]*0.85) {
}
goingUp = false;
}
}
}
freq =self.sampleRate/interp(result[returnIndex-1], result[returnIndex], result[returnIndex+1], returnIndex);
if(freq >= 27.5 && freq <= 4500.0) {
dispatch_async(dispatch_get_main_queue(), ^{
[delegate updatedPitch:freq];
});
}
self.running = NO;
}
float interp(float y1, float y2, float y3, int k);
float interp(float y1, float y2, float y3, int k) {
float d, kp;
d = (y3 - y1) / (2 * (2 * y2 - y1 - y3));
//printf("%f = %d + %f\n", k+d, k, d);
kp = k + d;
return kp;
}
@end
提前致谢！