Version 0.1.2 from FTP

git-svn-id: http://svn.digium.com/svn/asterisk/trunk@169 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 132 insertions, 0 deletions

diff --git a/codecs/lpc10/preemp.c b/codecs/lpc10/preemp.c
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+/*
+
+$Log$
+Revision 1.1  2000/01/05 08:20:39  markster
+Version 0.1.2 from FTP
+
+Revision 1.2  2000/01/05 08:20:39  markster
+Some OSS fixes and a few lpc changes to make it actually work
+
+ * Revision 1.1  1996/08/19  22:30:58  jaf
+ * Initial revision
+ *
+
+*/
+
+#ifdef P_R_O_T_O_T_Y_P_E_S
+extern int preemp_(real *inbuf, real *pebuf, integer *nsamp, real *coef, real *z__);
+#endif
+
+/*  -- translated by f2c (version 19951025).
+   You must link the resulting object file with the libraries:
+	-lf2c -lm   (in that order)
+*/
+
+#include "f2c.h"
+
+/* ******************************************************************* */
+
+/* 	PREEMP Version 55 */
+
+/* $Log$
+ * Revision 1.1  2000/01/05 08:20:39  markster
+ * Version 0.1.2 from FTP
+ *
+/* Revision 1.2  2000/01/05 08:20:39  markster
+/* Some OSS fixes and a few lpc changes to make it actually work
+/*
+ * Revision 1.1  1996/08/19  22:30:58  jaf
+ * Initial revision
+ * */
+/* Revision 1.3  1996/03/14  23:16:29  jaf */
+/* Just added a few comments about which array indices of the arguments */
+/* are used, and mentioning that this subroutine has no local state. */
+
+/* Revision 1.2  1996/03/11  23:23:34  jaf */
+/* Added a bunch of comments to an otherwise simple subroutine. */
+
+/* Revision 1.1  1996/02/07 14:48:48  jaf */
+/* Initial revision */
+
+
+/* ******************************************************************* */
+
+/*   Preemphasize speech with a single-zero filter. */
+/*  (When coef = .9375, preemphasis is as in LPC43.) */
+
+/* Inputs: */
+/*  NSAMP  - Number of samples to filter */
+/*  INBUF  - Input speech buffer */
+/*           Indices 1 through NSAMP are read. */
+/*  COEF   - Preemphasis coefficient */
+/* Input/Output: */
+/*  Z      - Filter state */
+/* Output: */
+/*  PEBUF  - Preemphasized speech buffer (can be equal to INBUF) */
+/*           Indices 1 through NSAMP are modified. */
+
+/* This subroutine has no local state. */
+
+/* Subroutine */ int preemp_(real *inbuf, real *pebuf, integer *nsamp, real *
+	coef, real *z__)
+{
+    /* System generated locals */
+    integer i__1;
+
+    /* Local variables */
+    real temp;
+    integer i__;
+
+/*       Arguments */
+/*       Local variables */
+
+/*       None of these need to have their values saved from one */
+/*       invocation to the next. */
+
+/*       Logically, this subroutine computes the output sequence */
+/*       pebuf(1:nsamp) defined by: */
+
+/*       pebuf(i) = inbuf(i) - coef * inbuf(i-1) */
+
+/*       where inbuf(0) is defined by the value of z given as input to */
+/*       this subroutine. */
+
+/*       What is this filter's frequency response and phase response? */
+
+/*       Why is this filter applied to the speech? */
+
+/*       Could it be more efficient to apply multiple filters */
+/*       simultaneously, by combining them into one equivalent filter? */
+
+/*       Are there ever cases when "factoring" one high-order filter into 
+*/
+/*       multiple smaller-order filter actually reduces the number of */
+/*       arithmetic operations needed to perform them? */
+/*       When I first read this subroutine, I didn't understand why the */
+/*       variable temp was used.  It seemed that the statements in the do 
+*/
+/*       loop could be replaced with the following: */
+
+/*           pebuf(i) = inbuf(i) - coef * z */
+/*           z = inbuf(i) */
+
+/*       The reason for temp is so that even if pebuf and inbuf are the */
+/*       same arrays in memory (i.e., they are aliased), then this */
+/*       subroutine will still work correctly.  I didn't realize this */
+/*       until seeing the comment after PEBUF above that says "(can be */
+/*       equal to INBUF)". */
+    /* Parameter adjustments */
+    --pebuf;
+    --inbuf;
+
+    /* Function Body */
+    i__1 = *nsamp;
+    for (i__ = 1; i__ <= i__1; ++i__) {
+	temp = inbuf[i__] - *coef * *z__;
+	*z__ = inbuf[i__];
+	pebuf[i__] = temp;
+/* L10: */
+    }
+    return 0;
+} /* preemp_ */
+