deemp.f,v

lpc10-15为美军2400bps语音压缩标准的C语音源代码。

head	1.3;
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symbols;
locks; strict;
comment	@* @;


1.3
date	96.03.20.15.54.37;	author jaf;	state Exp;
branches;
next	1.2;

1.2
date	96.03.14.22.11.13;	author jaf;	state Exp;
branches;
next	1.1;

1.1
date	96.02.07.14.44.53;	author jaf;	state Exp;
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next	;


desc
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1.3
log
@Added comments about which indices of array arguments are read or
written.

Added entry INITDEEMP to reinitialize the local state variables, if
desired.
@
text
@******************************************************************
*
*	DEEMP Version 48
*
* $Log: deemp.f,v $
* Revision 1.2  1996/03/14  22:11:13  jaf
* Comments added explaining which of the local variables of this
* subroutine need to be saved from one invocation to the next, and which
* do not.
*
* Revision 1.1  1996/02/07 14:44:53  jaf
* Initial revision
*
*
******************************************************************
*
*  De-Emphasize output speech with   1 / ( 1 - .75z**-1 )
*    cascaded with 200 Hz high pass filter
*    ( 1 - 1.9998z**-1 + z**-2 ) / ( 1 - 1.75z**-1 + .78z**-2 )
*  
*  WARNING!  The coefficients above may be out of date with the code
*  below.  Either that, or some kind of transformation was performed
*  on the coefficients above to create the code below.
*
* Input:
*  N  - Number of samples
* Input/Output:
*  X  - Speech
*       Indices 1 through N are read before being written.
* 
* This subroutine maintains local state from one call to the next.  If
* you want to switch to using a new audio stream for this filter, or
* reinitialize its state for any other reason, call the ENTRY
* INITDEEMP.
*
	SUBROUTINE DEEMP( X, N )

*       Arguments

	INTEGER N
	REAL X(N)

*       Local variables that need not be saved

	INTEGER K
	REAL DEI0

*       Local state

*       All of the locals saved below were not given explicit initial
*       values in the original code.  I think 0 is a safe choice.

	REAL DEI1, DEI2, DEO1, DEO2, DEO3

	SAVE DEI1, DEI2, DEO1, DEO2, DEO3

	DATA DEI1/0./, DEI2/0./, DEO1/0./, DEO2/0./, DEO3/0./

	DO K = 1,N
	   DEI0 = X(K)
	   X(K) = X(K) - 1.9998*DEI1 + DEI2
     1     + 2.5*DEO1 - 2.0925*DEO2 + .585*DEO3
	   DEI2 = DEI1
	   DEI1 = DEI0
	   DEO3 = DEO2
	   DEO2 = DEO1
	   DEO1 = X(K)
	END DO

	RETURN


	ENTRY INITDEEMP ()

	DEI1 = 0.
	DEI2 = 0.
	DEO1 = 0.
	DEO2 = 0.
	DEO3 = 0.

	RETURN

	END
@


1.2
log
@Comments added explaining which of the local variables of this
subroutine need to be saved from one invocation to the next, and which
do not.
@
text
@d6 5
d22 2
a23 1
*  below.
d27 1
a27 1
* In/Output:
d29 6
d43 1
a43 1
*       Local variables
d46 6
a51 1
	REAL DEI0, DEI1, DEI2, DEO1, DEO2, DEO3
d53 1
a53 2
*       NO SAVE NECESSARY  K
*       NO SAVE NECESSARY  DEI0
a54 1
	DATA DEI1/0./, DEI2/0./, DEO1/0./, DEO2/0./, DEO3/0./
d57 1
a57 4
*       WARNING!
*       
*       All of the locals saved above should be given explicit initial
*       values.  I think 0. is a good choice.
d71 12
@


1.1
log
@Initial revision
@
text
@d5 4
a8 1
* $Log$
d15 3
d25 4
a28 1
	INTEGER N, K
d30 4
d35 11
@