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wav file

Started by mmoctar July 3, 2009
Hi all,
I'm working on acoustic echo cancellation, my question is;
When I test an algorithm like LMS or NLMS should I change the scale of my
wave signal?
As pcm file are Q15 between 1 and -1, do I need to multiply my signal by
2^15 for test under matlab.
Like input=2^15*wavread('input.wav').

My question is relative to the fact that signal level have an impact on
algorithm performances.
thank you in advance.
Moctar

mmoctar wrote:

> Hi all, > I'm working on acoustic echo cancellation, my question is; > When I test an algorithm like LMS or NLMS should I change the scale of my > wave signal? > As pcm file are Q15 between 1 and -1, do I need to multiply my signal by > 2^15 for test under matlab. > Like input=2^15*wavread('input.wav'). > > My question is relative to the fact that signal level have an impact on > algorithm performances. > thank you in advance. > Moctar
> > >mmoctar wrote: > >> Hi all, >> I'm working on acoustic echo cancellation, my question is; >> When I test an algorithm like LMS or NLMS should I change the scale of
my
>> wave signal? >> As pcm file are Q15 between 1 and -1, do I need to multiply my signal
by
>> 2^15 for test under matlab. >> Like input=2^15*wavread('input.wav'). >> >> My question is relative to the fact that signal level have an impact
on
>> algorithm performances. >> thank you in advance. >> Moctar >
Why should the signal level impact on the algorithm performance?

On Jul 3, 9:35&#2013266080;am, "mmoctar" <mmoc...@gmail.com> wrote:
> Hi all, > I'm working on acoustic echo cancellation, my question is; > When I test an algorithm like LMS or NLMS should I change the scale of my > wave signal? > As pcm file are Q15 between 1 and -1, do I need to multiply my signal by > 2^15 for test under matlab. > Like input=2^15*wavread('input.wav'). > > My question is relative to the fact that signal level have an impact on > algorithm performances. > thank you in advance. > Moctar
> >Why should the signal level impact on the algorithm performance?
The impact is in the choice of the step size you have to choose. When your signal is high level you must choose a small step size (for stability) and the smallest the step size is the slower your algo 'll be. And when the algo use a power estimation (transform or freq lms) the result is completely different.
> >On Jul 3, 9:35=A0am, "mmoctar" <mmoc...@gmail.com> wrote: >> Hi all, >> I'm working on acoustic echo cancellation, my question is; >> When I test an algorithm like LMS or NLMS should I change the scale of
my
>> wave signal? >> As pcm file are Q15 between 1 and -1, do I need to multiply my signal
by
>> 2^15 for test under matlab. >> Like input=3D2^15*wavread('input.wav'). >> >> My question is relative to the fact that signal level have an impact
on
>> algorithm performances. >> thank you in advance. >> Moctar > >
Moctar
Suppose you have developed the floating point algorithm and it works
well, then whatever Q format you use, just scale the step size
proportionally,  you should be fine.


On Jul 3, 5:06&#2013266080;pm, "mmoctar" <mmoc...@gmail.com> wrote:
> >Why should the signal level impact on the algorithm performance? > > The impact is in the choice of the step size you have to choose. When your > signal is high level you must choose a small step size (for stability) and > the smallest the step size is the slower your algo 'll be. And when the > algo use a power estimation (transform or freq lms) the result is > completely different. > > > > >On Jul 3, 9:35=A0am, "mmoctar" <mmoc...@gmail.com> wrote: > >> Hi all, > >> I'm working on acoustic echo cancellation, my question is; > >> When I test an algorithm like LMS or NLMS should I change the scale of > my > >> wave signal? > >> As pcm file are Q15 between 1 and -1, do I need to multiply my signal > by > >> 2^15 for test under matlab. > >> Like input=3D2^15*wavread('input.wav'). > > >> My question is relative to the fact that signal level have an impact > on > >> algorithm performances. > >> thank you in advance. > >> Moctar > > Moctar