read audio signal. How to choose the right number of input channels???

I'm trying to read audio from a file, and these are the properties:

>> PhaseVocoderMATLAB002

reader = 

  dsp.AudioFileReader with properties:

           Filename: '/Users/FatimAlansari/Documents/MATLAB/Examples/signal/ResamplingALinearSequenceExample/HelloWorld.wav'
          PlayCount: 1
    SamplesPerFrame: 64
     OutputDataType: 'double'
         SampleRate: 44100
          ReadRange: [1 Inf]


buff = 

  dsp.Buffer with properties:

               Length: 256
        OverlapLength: 192
    InitialConditions: 0


win = 

  dsp.Window with properties:

       WindowFunction: 'Hanning'
    WeightsOutputPort: false
             Sampling: 'Periodic'

  Show all properties


Fs =

       44100


player = 

  audioDeviceWriter with properties:

        Device: 'Default'
    SampleRate: 44100

  Show all properties


player = 

  audioDeviceWriter with properties:

        Device: 'Default'
    SampleRate: 44100

  Show all properties
  

and a got the following error when coming to Play time-stretched signal...

Error using audioDeviceWriter/setup
The number of input channels must be less than or equal to 255.

Error in audioDeviceWriter/setupImpl

Error in PhaseVocoderMATLAB002 (line 150)
player(loggedSpeech.');

i replace the number of channel with 255 and still get the same error.

how can i choose the right number of channel to fix this error

[Jan]

Please show us the code instead of its output. It sounds like setting te number of channels to 255 did not work, so we need to see the code to find the error.

[fatima alansari]

%% Pitch Shifting and Time Dilation Using a Phase Vocoder in MATLAB
% This example shows how to implement a phase vocoder to time stretch and
% pitch scale an audio signal. 
WindowLen = 256;
AnalysisLen = 64;
SynthesisLen = 90;
Hopratio = SynthesisLen/AnalysisLen;
%%
% Create a System object to read in the input speech signal from an audio
% file.
%'SpeechDFT-16-8-mono-5secs.wav'
%
reader = dsp.AudioFileReader('HelloWorld.wav', ...
  'SamplesPerFrame',AnalysisLen, ...
  'OutputDataType','double')
%%
% Create a buffer System object, which is used for the ST-FFT.
buff = dsp.Buffer(WindowLen, WindowLen - AnalysisLen)
% Create a Window System object, which is used for the ST-FFT. This object
% applies a window to the buffered input data.
win = dsp.Window('Hanning', 'Sampling', 'Periodic')
%%
% Create an FFT System object, which is used for the ST-FFT.
dft = dsp.FFT;
% Create an IFFT System object, which is used for the IST-FFT.
idft = dsp.IFFT('ConjugateSymmetricInput',true,'Normalize',false)
%%
% Create a System object to play original speech signal.
Fs = 44100                          %<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
player = audioDeviceWriter('SampleRate',Fs, ...
    'SupportVariableSizeInput',true, ...
    'BufferSize',512)            %<<<<<<< i replaced 512 with 255
% Create a System object to log your data.
logger = dsp.SignalSink
%%
% Initialize the variables used in the processing loop.
yprevwin = zeros(WindowLen-SynthesisLen,1);
gain = 1/(WindowLen*sum(hanning(WindowLen,'periodic').^2)/SynthesisLen);
unwrapdata = 2*pi*AnalysisLen*(0:WindowLen-1)'/WindowLen;
yangle = zeros(WindowLen,1);
firsttime = true
%% Stream Processing Loop
% Now that you have instantiated your System objects, you can create a
% processing loop that performs time stretching on the input signal. The
% loop is stopped when you reach the end of the input file, which is
% detected by the |AudioFileReader| System object.
while ~isDone(reader)
    y = reader();
    player(y);   % Play back original audio
    % ST-FFT
    % FFT of a windowed buffered signal
    yfft = dft(win(buff(y)));
    % Convert complex FFT data to magnitude and phase.
    ymag       = abs(yfft);
    yprevangle = yangle;
    yangle     = angle(yfft);
    % Synthesis Phase Calculation
    % The synthesis phase is calculated by computing the phase increments
    % between successive frequency transforms, unwrapping them, and scaling
    % them by the ratio between the analysis and synthesis hop sizes.
    yunwrap = (yangle - yprevangle) - unwrapdata;
    yunwrap = yunwrap - round(yunwrap/(2*pi))*2*pi;
    yunwrap = (yunwrap + unwrapdata) * Hopratio;
    if firsttime
        ysangle = yangle;
        firsttime = false;
    else
        ysangle = ysangle + yunwrap;
    end
    % Convert magnitude and phase to complex numbers.
    ys = ymag .* complex(cos(ysangle), sin(ysangle));
    % IST-FFT
    ywin  = win(idft(ys));    % Windowed IFFT
    % Overlap-add operation
    olapadd  = [ywin(1:end-SynthesisLen,:) + yprevwin; ...
                ywin(end-SynthesisLen+1:end,:)];
    yistfft  = olapadd(1:SynthesisLen,:);
    yprevwin = olapadd(SynthesisLen+1:end,:);
    % Compensate for the scaling that was introduced by the overlap-add
    % operation
    yistfft = yistfft * gain;
    logger(yistfft);     % Log signal
end
%% Release
% Here you call the release method on the System objects to close any open 
% files and devices.
release(reader);
%% Play the Time-Stretched Signals
% 
loggedSpeech = logger.Buffer(200:end)';
player = audioDeviceWriter('SampleRate', Fs, ...
    'SupportVariableSizeInput', true, ...
    'BufferSize', 255)      %<<<<<<< i replaced 512 with 255 and still have the same error
% Play time-stretched signal
disp('Playing time-stretched signal...');
player(loggedSpeech.');
%% Summary
% This example shows the implementation of a phase vocoder to perform time
% stretching and pitch scaling of a speech signal. You can hear these
% time-stretched and pitch-scaled signals when you run the example.
%% References
% A. D. Gotzen, N. Bernardini and D. Arfib, "Traditional Implementations of
% a Phase-Vocoder: The Tricks of the Trade," Proceedings of the COST G-6
% Conference on Digital Audio Effects (DAFX-00), Verona, Italy, December
% 7-9, 2000.
displayEndOfDemoMessage(mfilename)

i got the following error....

Error using audioDeviceWriter/setup
The number of input channels must be less than or
equal to 255.
Error in audioDeviceWriter/setupImpl
Error in PhaseVocoderMATLAB002 (line 156)
player(loggedSpeech.');