random.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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comment	@* @;


1.3
date	96.03.20.16.13.54;	author jaf;	state Exp;
branches;
next	1.2;

1.2
date	96.03.14.22.25.29;	author jaf;	state Exp;
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next	1.1;

1.1
date	96.02.07.14.49.01;	author jaf;	state Exp;
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desc
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1.3
log
@Rearranged comments a little bit, and added comments explaining that
even though there is local state here, there is no need to create an
ENTRY for reinitializing it.
@
text
@***********************************************************************
*
*	RANDOM Version 49
*
* $Log: random.f,v $
* Revision 1.2  1996/03/14  22:25:29  jaf
* Just rearranged the comments and local variable declarations a bit.
*
* Revision 1.1  1996/02/07 14:49:01  jaf
* Initial revision
*
*
**********************************************************************
*
*  Pseudo random number generator based on Knuth, Vol 2, p. 27.
*
* Function Return:
*  RANDOM - Integer variable, uniformly distributed over -32768 to 32767
* 
* This subroutine maintains local state from one call to the next.
* In the context of the LPC10 coder, there is no reason to reinitialize
* this local state when switching between audio streams, because its
* results are only used to generate noise for unvoiced frames.
*
	FUNCTION RANDOM ()
	INTEGER RANDOM

*	Parameters/constants

	INTEGER MIDTAP, MAXTAP
	PARAMETER (MIDTAP=2, MAXTAP=5)

*       Local state

	INTEGER J, K
	INTEGER*2 Y(MAXTAP)

	SAVE J, K, Y

	DATA J/MIDTAP/, K/MAXTAP/
	DATA Y /-21161, -8478, 30892,-10216, 16950/

*   The following is a 16 bit 2's complement addition,
*   with overflow checking disabled

	Y(K) = Y(K) + Y(J)
	RANDOM = Y(K)
	K = K - 1
	IF (K .LE. 0) K = MAXTAP
	J = J - 1
	IF (J .LE. 0) J = MAXTAP

	RETURN
	END
@


1.2
log
@Just rearranged the comments and local variable declarations a bit.
@
text
@d6 3
d19 5
d28 2
d33 1
a33 1
*       Local variables
d37 1
d39 2
a41 1
	DATA J/MIDTAP/, K/MAXTAP/
@


1.1
log
@Initial revision
@
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@d5 4
a8 1
* $Log$
d18 3
a20 1
	INTEGER RANDOM, J, K, MIDTAP, MAXTAP
d22 4
@