Newsgroups: comp.speech,comp.dsp
Path: lyra.csx.cam.ac.uk!warwick!pipex!howland.reston.ans.net!europa.eng.gtefsd.com!MathWorks.Com!zombie.ncsc.mil!afterlife!jpcampb
From: jpcampb@afterlife.ncsc.mil (Joe Campbell)
Subject: Re: Need Help on AMDF (Average Magnitude Difference Function)
Message-ID: <1994Apr9.203242.13326@afterlife.ncsc.mil>
Organization: The Great Beyond
References: <CnpKGo.DAv@ecf.toronto.edu>
Date: Sat, 9 Apr 1994 20:32:42 GMT
Lines: 38
Xref: lyra.csx.cam.ac.uk comp.speech:2264 comp.dsp:6467

In article <CnpKGo.DAv@ecf.toronto.edu>,
LIU  CHEUNG WAH STEPHEN <liuca@ecf.toronto.edu> wrote:
>	I am trying to write a C program to implement the AMDF (average
>magnitude difference function) for pitch, voiced/unvoiced estimation.
>But I do not have the COMPLETE method. In particular, I would like
>more details in the following
>(1) how many lag value should I try before I stop:
>	d(k) = SUM x(n) - x(n+k) n=0..N-1, N=frame length, k=1,2,... ??
>     that is, how many k should I try.
>(2) another thing is, from the above equation, it seems that I have
>    to use values from the next frame too, am I right? But if it is
>    true, the pitch period found may not be the right value for
>    the CURRENT frame... I am confused.
>(3) after I have found the set of d(k) values, what kind of threshold(s)
>    should I use for comparison in order to consider them as pitch?
>(4) assume now question (3) above is solved, and now that I have a 
>    set of k values. But if the spacing between the k values are
>    very uneven, then how am I going to determine the pitch values?

Welcome to "pitch!"  Since this sounds like a school project, I better
let you find the answers to your questions in:

Wolfgang Hess, Pitch Determination of Speech Signals: Algorithms and
Devices, Springer-Verlag, 1983.

Thomas E. Tremain, "The Government Standard Linear Predictive Coding
Algorithm:  LPC-10," Speech Technology Magazine, April 1982, p. 40-49.
 
Panos E. Papamichalis, Practical Approaches to Speech Coding,
Prentice-Hall, 1987.

Good luck,
Joe
-- 
.............................................................................
; Dr. Campbell  N3JBC  jpcampb@afterlife.ncsc.mil  74040.305@compuserve.com ;
; Speaking for myself     Happiness = Reality - Expectations, Click & Clack ;
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