# Complex Cepstral Transform on Audio in MATLAB

Hello I am trying to computer the Complex Cepstral Transform of an audio signal. I am using wavread to get an array of data type double precision. However, when I try to use cceps to do the Complex Cepstral Transform, I get the following error:

Error using cceps>chkinput (line 157)
The input signal X must be real.

Error in cceps (line 73)
chkinput(x);


Is there something I am doing wrong or is there another way to do this transform? Thank you!

Also, I tried computing this manually using the definition of the complex cepstral transform as follows:

C=ifft(ln(fft(f)))


where f is the array of double precision audio data. However, this returns the error:  Undefined function 'ln' for input arguments of type 'double'.

• The natural logarithm is called 'log' in Matlab. – Matt L. Jul 11 '13 at 9:27