Re: Zero Crossing Rate - optimize implementation

[James Sherman Jr.]

Well, I think the biggest thing is that you can use that sign operates per element when you give it a vector, so to find where the zero crossings are you can simply do:

zcr = diff(sign(s))~=0;

Then you can loop over this to do your summations of frames.  Something like:

index = 1;

frame_start = 1:framesize:N;

zcr_rate = zeros(1, length(frame_start));

for starttime = frame_start,

   endtime = min(starttime+framesize-1, N);

   zcr_rate(index) = sum(zcr(starttime:endtime));

   index = index + 1;

end

On Fri, May 7, 2010 at 8:09 PM, jacek grabowski <address@hidden> wrote:

Hello,

I would like to ask You for any idea how to optimize following code:

s=wavread('sample.wav');
N=length(s)
framesize=2000;
frame_lim=[1:framesize:N-1];
FN=length(frame_lim);
zcr=zeros(1,FN-1);
tic()
for i=1:FN-1
   for k=frame_lim(1,i):frame_lim(1,i+1)
       if sign(s(k)) != sign (s(k+1))
        zcr(i)=zcr(i)+1;
       endif
   endfor
endfor
toc()

N =  236352
Elapsed time is 41.39265 seconds.

This is my first week with Octave, so forgive me any stupid question ... :)
Thank you very much.

--
Jacek Grabowski
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