Newsgroups: comp.speech,comp.dsp
Path: lyra.csx.cam.ac.uk!warwick!pipex!howland.reston.ans.net!cs.utexas.edu!utnut!cannon.ecf!liuca
From: liuca@ecf.toronto.edu (LIU  CHEUNG WAH STEPHEN)
Subject: Need Help on AMDF (Average Magnitude Difference Function)
Message-ID: <CnpKGo.DAv@ecf.toronto.edu>
Sender: news@ecf.toronto.edu (News Administrator)
Organization: University of Toronto, Engineering Computing Facility
Date: Mon, 4 Apr 1994 00:09:58 GMT
Lines: 22
Xref: lyra.csx.cam.ac.uk comp.speech:2233 comp.dsp:6361

	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?

	Any suggestions?
	Also, it will be helpful if there is some materials that I can
refer to.
	Thank you very much. And please reply by email if possible.

