How to change the resolution of audio data using MATLAB?

jean young — Wed, 19 Aug 2009 11:02:02 -0400

Hi, I have some audio data stored in .wav file. I got them using wavread function in MATLAB and found the sampling rate is 8-kHz and the resolution is 16 bits. My supervisor asked me to change the resolution to 12 bits and 10 bits then I can see the difference.

The problem is that most softwares (e.g. wavwrite in MATLAB, Cool Edit) only do the transform among 8 bits, 16 bits, 24 bits and 32 bits. Therefore I tried to write code to do this myself (see my code below).
%-------------------------------------------------------
nbits = 10; % resolution after transform
[src,fs,bits] = wavread('audio');
y = src(:);
y1 = y*(2^bits/2)+(2^bits/2);
numSnapshot = size(y1,1);
ini = bits-nbits+1;
for n = 1:numSnapshot
    x1 = dec2binvec(y1(n));
    x2 = x1(ini:end);
    x3(n,1) = binvec2dec(x2);
end
y2 = (x3-(2^nbits/2))/(2^nbits/2);
dif = y-y2;
plot(1:numSnapshot,y2,'k-',1:numSnapshot,dif,'r-')
%-------------------------------------------------------
However, I feel this method is somewhat stupid because it takes long time in the loops, especially when the audio data has large size. :-(

Anyone knows better method? Any help is highly appreciated!

Re: How to change the resolution of audio data using MATLAB?

dbd — Wed, 19 Aug 2009 15:44:40 -0400

On Aug 19, 4:02 am, "jean young" <jean_young...@yahoo.com> wrote:
> Hi, I have some audio data stored in .wav file. I got them using wavread function in MATLAB and found the sampling rate is 8-kHz and the resolution is 16 bits. My supervisor asked me to change the resolution to 12 bits and 10 bits then I can see the difference.
>
> The problem is that most softwares (e.g. wavwrite in MATLAB, Cool Edit) only do the transform among 8 bits, 16 bits, 24 bits and 32 bits. Therefore I tried to write code to do this myself (see my code below).
> ...
> Anyone knows better method? Any help is highly appreciated!

A faster approximate method might be:

nbitdata = round(2^(nbit-1)*src)/2^(nbit-1);

Dale B. Dalrymple

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How to change the resolution of audio data using MATLAB?

Re: How to change the resolution of audio data using MATLAB?