Phase Vocoder的补充完善，Matlab音频变速不变调、变调不变速

之前有站内朋友介绍了国外的Phase Vocoder，Matlab音频变速不变调、变调不变速（Phase Vocoder）_cyz0612的博客-CSDN博客_matlab变调不变速代码参考这篇文章，我成功实现了变速不变调，我将其命名为speedShift函数，放在下面供后来的朋友交流学习。

function [outputVector] = speedShift(inputVector, windowSize, hopSize, t)

%% Parameters

% Window size
winSize = windowSize;
% Space between windows
hop = hopSize;
%t是函数的输入
step=12*log2(1/t);
% Pitch scaling factor
alpha = 2^(step/12);

% Intermediate constants
hopOut = round(alpha*hop);

% Hanning window for overlap-add
wn = hann(winSize*2+1);
wn = wn(2:2:end);

%% Source file

x = inputVector;

% Rotate if needed
if size(x,1) < size(x,2)
   
    x = transpose(x);

end

x = [zeros(hop*3,1) ; x];

%% Initialization

% Create a frame matrix for the current input
[y,numberFramesInput] = createFrames(x,hop,winSize);

% Create a frame matrix to receive processed frames
numberFramesOutput = numberFramesInput;
outputy = zeros(numberFramesOutput,winSize);

% Initialize cumulative phase
phaseCumulative = 0;

% Initialize previous frame phase
previousPhase = 0;

for index=1:numberFramesInput
    
%% Analysis
    
    % Get current frame to be processed
    currentFrame = y(index,:);
    
    % Window the frame
    currentFrameWindowed = currentFrame .* wn' / sqrt(((winSize/hop)/2));
    
    % Get the FFT
    currentFrameWindowedFFT = fft(currentFrameWindowed);
    
    % Get the magnitude
    magFrame = abs(currentFrameWindowedFFT);
    
    % Get the angle
    phaseFrame = angle(currentFrameWindowedFFT);
    
%% Processing    

    % Get the phase difference
    deltaPhi = phaseFrame - previousPhase;
    previousPhase = phaseFrame;
    
    % Remove the expected phase difference
    deltaPhiPrime = deltaPhi - hop * 2*pi*(0:(winSize-1))/winSize;
    
    % Map to -pi/pi range
    deltaPhiPrimeMod = mod(deltaPhiPrime+pi, 2*pi) - pi;
     
    % Get the true frequency
    trueFreq = 2*pi*(0:(winSize-1))/winSize + deltaPhiPrimeMod/hop;

    % Get the final phase
    phaseCumulative = phaseCumulative + hopOut * trueFreq;    
    
    % Remove the 60 Hz noise. This is not done for now but could be
    % achieved by setting some bins to zero.
   
%% Synthesis    
    
    % Get the magnitude
    outputMag = magFrame;
    
    % Produce output frame
    outputFrame = real(ifft(outputMag .* exp(j*phaseCumulative)));
     
    % Save frame that has been processed
    outputy(index,:) = outputFrame .* wn' / sqrt(((winSize/hopOut)/2));
        
end

%% Finalize

% Return the result
outputVector =fusionFrames(outputy,hopOut);

return

 代码下载：Guitar Pitch Shifter - Performances

使用方式非常简单，只需要将下载的三个m文件放到工作目录下面直接调用就行了，需要注意的就是新版的matlab在读取wav文件时，不能使用旧的函数，使用新的audioread函数，播放函数也需要更新为sound函数。而且调用pitchShift和speedShift函数的时候，如果wav信号是双声道的信号，应该先进行左右声道的平均，即将双声道转换成单声道再输入。

[x,Fs]=audioread('sample.wav');%读入wav音频文件
leftChannel = x(:,1);
rightChannel = x(:,2);
averageBoth = (leftChannel + rightChannel) / 2;%左右声道求平均 

播放函数：

sound(x,Fs);   %播放原信号音频