Error in Matlab Coder: "Property 'pBuffer.Cache' is undefined on some execution paths but is used inside the called function."

I am trying to create a mex file based on the code below using the Matlab Coder app. I want to implement an audio recording of 10 seconds in length at 48000 Hz of a sampling rate from my sound card and store the data in array x for further calculations.

function [x] = AudioRec()

deviceReader = audioDeviceReader('SampleRate',48000,'Device','"What U Hear" (Sound Blaster Audigy 5/Rx)');

buff = dsp.AsyncBuffer('Capacity',10*48000);

N = deviceReader.SamplesPerFrame;

while buff.NumUnreadSamples+N <= buff.Capacity

audioIn = deviceReader();

write(buff,audioIn);

end

release(deviceReader);

x = read(buff);

end

Matlab Coder gives me this error message:

Property 'pBuffer.Cache' is undefined on some execution paths but is used inside the called function.

Error in == AudioRec Line 16 Column 10

Code generation failed View Error Report

How can i solve the problem?

Answer 1

[jibrahim]

He Bernd,

I suspect coder is not sure this while loop will ever be entered. This should work (I added a call to write outside the while loop)

function [x] = AudioRec()
deviceReader = audioDeviceReader('SampleRate',48000);
buff = dsp.AsyncBuffer('Capacity',10*48000);
N = deviceReader.SamplesPerFrame;
write(buff,zeros(N,1));
while buff.NumUnreadSamples+N <= buff.Capacity
    audioIn = deviceReader();
    write(buff,audioIn);
end
release(deviceReader);
x = read(buff);
end

[Bernd]

Thank you for your quick reply! Your code works and the MEX file is generated by the Matlab Coder.