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Phase Vocoder

Phase Vocoder. Colter McQuay. Phase Vocoder Structure. Input x[ nTs ]. Analyze. Effect Specific Code. Synthesize. Output y[ nTs ]. Time Stretch Effect. %% Load Signal From File [ x Fs]= wavread ('../x1.wav'); x=x(:,1 )'; % Convert to mono windowSize =2048 ; % Set up window Size

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Phase Vocoder

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  1. Phase Vocoder Colter McQuay

  2. Phase Vocoder Structure Input x[nTs] Analyze Effect Specific Code Synthesize Output y[nTs]

  3. Time Stretch Effect %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono windowSize=2048; % Set up window Size stretchRatio=2.5; % Our time Stretch Ratio anHop=128; % Analysis Hop Size % Calculate Synthesis Hop Size based on ratio synthHop=round(anHop*stretchRatio); % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); % Generate output (don’t modify phase or % magnitudes) y=pvSynthesize(mag,phase,synthHop,anHop,1); Tom’s Diner Original Stretched by 2.5 Compressed by 0.5 Audacity Time Stretch

  4. Pitch Shift Effect Pitch Shifted by 0.7 %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono windowSize=2048; % Set up window Size pitchRatio=0.7; % Our pitch shift Ratio anHop=256; % Analysis Hop Size % Calculate Synthesis Hop Size based on ratio synthHop=round(anHop*pitchRatio); % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); % Generate output (don’t modify phase or % magnitudes) y=pvSynthesize(mag,phase,synthHop,anHop,1); % Resample output to make pitch shifted % version of input y=resample(y,anHop,synthHop); Pitch Shifted by 1.4

  5. Robotization %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono windowSize=512; % Set up window Size anHop=128; % Analysis Hop Size synthHop=anHop; % Synthesis Hop Size % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); % Get size of phase array [pRowspCols]=size(phase); % Set new phases to zero phase=zeros(pRows,pCols); % Reconstruct Output Signal y=pvSynthesize(mag,phase,synthHop,anHop,1); Window = 1024 Hop=512 Window = 512 Hop=128

  6. Whisperization Whisperization %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono windowSize=512; % Set up window Size anHop=128; % Analysis Hop Size synthHop=anHop; % Synthesis Hop Size % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); % Get size of phase array [pRowspCols]=size(phase); % De-Correlate phases by randomizing phase=2*pi*rand(pRows,pCols); % Reconstruct Output Signal y=pvSynthesize(mag,phase,synthHop,anHop,1);

  7. Isolation of Stable & Transient Components %% SOUND FILE [x Fs]=wavread('../stableTest.wav'); x=x(:,1)'; windowSize=1024; anHop=512; synthHop=anHop; %Analyze Input Signal [mag phase]=pvAnalyze(x,windowSize,anHop); [pRowspCols]=size(phase); % Set Threshold thresh=.5; % Pre-allocate new phase and magnitude arrays newPhase=zeros(pRows,pCols); newMag=zeros(pRows,pCols); % make first window of new phase array equal to original phase newPhase(1,:)=phase(1,:); % nominal phase increment for each bin omega_k=2*pi*[0:pCols-1]./pCols; % Iterate through all windows fori = 2:pRows % Calculate the target phase for each bin based on previous phase target_phase=phase(i-1,:)+omega_k*anHop; % Calculate deviation from the target phase deviation_phase=princarg(phase(i,:)-target_phase); % Set all bins either outside or inside the threshold to zero % NOTE: if abs(deviation_phase)<thresh is used, the stable components % will be kept. If abs(deviation_phase)>thresh the transient % components will be kept newPhase(i,:)=phase(i,:).*(abs(deviation_phase)<thresh); newMag(i,:)=mag(i,:).*(abs(deviation_phase)<thresh); end % Reconstruct output signal y=pvSynthesize(newMag,newPhase,synthHop,anHop,1); Original Pad & Drums Transient Components Stable Components

  8. Filter Filtered Signal %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono windowSize=2048; % Set up window Size anHop=256; % Analysis Hop Size synthHop=anHop; % Synthesis Hop Size b=[1 -1]; % Filter numerator Coefficients a=[1 -1.7718 0.9009]; % Filter Denominator % Get Frequency Response of Filter filterCoefs=freqz(b,a,windowSize)'; % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); % Get size of magnitude array [mRowsmCols]=size(mag); % Multiply the filter frequency response with % The time frequency data in each window for i = 1:mRows mag(i,:)=mag(i,:).*abs(filterCoefs); phase(i,:)=phase(i,:)+angle(filterCoefs); End % Reconstruct Output Signal y=pvSynthesize(mag,phase,synthHop,anHop,1);

  9. De-Noise %% Load Signal From File [x Fs]=wavread('../x1.wav'); x=x(:,1)';% Convert to mono noise=0.01*randn(1,length(x)); % Create a noise signal x=x+noise; % Add noise to input windowSize=2048; % Set up window Size anHop=256; % Analysis Hop Size synthHop=anHop; % Synthesis Hop Size % Analyze input signal [mag phase]=pvAnalyze(x,windowSize,anHop); coef=0.0015;% Set up de-noising coefficient f=mag.*exp(j*phase); % Set up frequency vector r = mag/windowSize; % Get r parameter for de-noising newF = f.*r./(r+coef); % Remove noise based on coef newMag=abs(newF); % get new magnitude newPhase=angle(newF); % get new phase % Reconstruct Output Signal y=pvSynthesize(newMag,newPhase,synthHop,anHop,1); Noisy Signal De-Noised Signal

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