How physcoacoustic model is generated . I was reading noise masking .
I have understood that FFT of 2048 samples is used for finding tone masking
.
And MDCT of same samples is used for noise masking .
Now while caculating noise masking , logmdct input is used . And function
bark_noise_hybridmp is called . In that function some mathematical
computation is done and
noise is calculate . ( noise[i] = R - offset ) Can anyone explain me what
it is .?
<p> logmask is the output of bark_noise_hybridmp ( fun 1)
why it is substracted and again passed to bark_noise_hybridmp ..?
( work[i]=logmdct[i]-logmask[i];)
What is the algorithm of noise masking.?
<p>----------------------------------------------------------------------------
-----------------------------------------------
void _vp_noisemask(vorbis_look_psy *p,
float *logmdct,
float *logmask){
int i,n=p->n;
float *work=alloca(n*sizeof(*work));
bark_noise_hybridmp(n,p->bark,logmdct,logmask,
140.,-1);
for(i=0;i<n;i++)work[i]=logmdct[i]-logmask[i];
bark_noise_hybridmp(n,p->bark,work,logmask,0.,
p->vi->noisewindowfixed);
for(i=0;i<n;i++)work[i]=logmdct[i]-work[i];
for(i=0;i<n;i++){
int dB=logmask[i]+.5;
if(dB>=NOISE_COMPAND_LEVELS)dB=NOISE_COMPAND_LEVELS-1;
if(dB<0)dB=0;
logmask[i]= work[i]+p->vi->noisecompand[dB];
}
}
----------------------------------------------------------------------------
-----------------------------------------------
<p>regards
Leena
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