quantize/digitize wav file

how can I digitize/quantize .wav file in matlab

well, basically i am trying to modulate it,

[X, Fs, nbits] = wavread('filename');

M=16;

modulated_sig=qammod(X,M);

but it keeps giving me an error saying

??? Error using ==> qammod at 39 Elements of input X must be integers in the range [0, M-1]

[jessica david]

I am guessing, i need to digitize it or something

Answer 1

[Walter Roberson]

You need to quantize, just like you did for your generated signal in your earlier versions.

[jessica david]

in the previous versions, X was of size N x 1; for a wav file, its size would be N x 2; and the function quantiz only takes N x 1;

it gives an error saying

??? Error using ==> quantiz at 32

The input signal must be a real vector.

[Walter Roberson]

http://www.mathworks.com/help/toolbox/comm/ref/qammod.html documents that if there are multiple rows in x that the columns will be processed independently, so it is fine to pass multiple columns to qammod. So just process the channels of the wav file through quantize independently and paste the result together:

qX = [quantiz(X(:,1),...,0:M-1), quantiz(X(:,2),...,0:M-1];

and pass qX to qammod.