The smooth is for LPC coefficients calculation. When G.723.1 calculates
pitch by open-loop or close-loop pitch predictor, it uses the the original
signal source not the smoothed one.
From: gray_1024 [mailto:]
Sent: Friday, March 28, 2003 7:51 AM
To: Zhou Yidan (COM AC CE M external)
Subject: Re: What's the meaning of the binomial coefficients in G.723.1 LPC
analysis? As you said, its purpose is to smooth the spectral envolope when the
pitch is shorter than one frame. But this process is before the
process of pitch estimation, how do you know the pitch then?
--- In , "Yidan Zhou
<ZhouY.external@i...>" <ZhouY.external@i...> wrote:
> Now I know the answer to it.
> This extra windowing is called 'Lag windowing'. Its purpose is to
> smooth the short-term spectral envolope when the pitch is shorter
> than one frame.
> Yidan Zhou
> --- In , "Yidan Zhou" <yidanzhou@y...>
> > Hi all,
> > Now I am reading the standard documents and reference source
> > of G.723.1. There is an extra windowing multiplication in between
> > Levinson-Durbin recursion and autocorrelation coefficient
> > calculation. But I do not know why this extra step is necessary.
> > Could anybody give me clue?
> > Thanks in advance!
> > Best regards,
> > Yidan Zhou