From 30325d24d107dbf133da39f7c96d1510fd1c9449 Mon Sep 17 00:00:00 2001
From: erdgeist <erdgeist@erdgeist.org>
Date: Fri, 15 Aug 2025 12:42:40 +0200
Subject: Bump to codec2 version 1.2.0

---
 lpc.c | 223 +++++++++++++++++++++++++++++-------------------------------------
 1 file changed, 97 insertions(+), 126 deletions(-)

(limited to 'lpc.c')

diff --git a/lpc.c b/lpc.c
index 31442cd..3117a1a 100644
--- a/lpc.c
+++ b/lpc.c
@@ -25,16 +25,18 @@
   along with this program; if not, see <http://www.gnu.org/licenses/>.
 */
 
-#define LPC_MAX_N 512		/* maximum no. of samples in frame */
-#define PI 3.141592654		/* mathematical constant */
+#define LPC_MAX_N 512  /* maximum no. of samples in frame */
+#define PI 3.141592654 /* mathematical constant */
 
 #define ALPHA 1.0
-#define BETA  0.94
+#define BETA 0.94
+
+#include "lpc.h"
 
 #include <assert.h>
 #include <math.h>
+
 #include "defines.h"
-#include "lpc.h"
 
 /*---------------------------------------------------------------------------*\
 
@@ -42,29 +44,25 @@
 
   Pre-emphasise (high pass filter with zero close to 0 Hz) a frame of
   speech samples.  Helps reduce dynamic range of LPC spectrum, giving
-  greater weight and hense a better match to low energy formants.
+  greater weight and hence a better match to low energy formants.
 
   Should be balanced by de-emphasis of the output speech.
 
 \*---------------------------------------------------------------------------*/
 
-void pre_emp(
-  float  Sn_pre[], /* output frame of speech samples                     */
-  float  Sn[],	   /* input frame of speech samples                      */
-  float *mem,      /* Sn[-1]single sample memory                         */
-  int   Nsam	   /* number of speech samples to use                    */
-)
-{
-    int   i;
-
-    for(i=0; i<Nsam; i++) {
-	Sn_pre[i] = Sn[i] - ALPHA * mem[0];
-	mem[0] = Sn[i];
-    }
+void pre_emp(float Sn_pre[], /* output frame of speech samples */
+             float Sn[],     /* input frame of speech samples     */
+             float *mem,     /* Sn[-1]single sample memory     */
+             int Nsam /* number of speech samples to use                    */
+) {
+  int i;
 
+  for (i = 0; i < Nsam; i++) {
+    Sn_pre[i] = Sn[i] - ALPHA * mem[0];
+    mem[0] = Sn[i];
+  }
 }
 
-
 /*---------------------------------------------------------------------------*\
 
   de_emp()
@@ -73,23 +71,19 @@ void pre_emp(
 
 \*---------------------------------------------------------------------------*/
 
-void de_emp(
-  float  Sn_de[],  /* output frame of speech samples                     */
-  float  Sn[],	   /* input frame of speech samples                      */
-  float *mem,      /* Sn[-1]single sample memory                         */
-  int    Nsam	   /* number of speech samples to use                    */
-)
-{
-    int   i;
-
-    for(i=0; i<Nsam; i++) {
-	Sn_de[i] = Sn[i] + BETA * mem[0];
-	mem[0] = Sn_de[i];
-    }
+void de_emp(float Sn_de[], /* output frame of speech samples */
+            float Sn[], /* input frame of speech samples                      */
+            float *mem, /* Sn[-1]single sample memory                         */
+            int Nsam    /* number of speech samples to use                    */
+) {
+  int i;
 
+  for (i = 0; i < Nsam; i++) {
+    Sn_de[i] = Sn[i] + BETA * mem[0];
+    mem[0] = Sn_de[i];
+  }
 }
 
-
 /*---------------------------------------------------------------------------*\
 
   hanning_window()
@@ -98,16 +92,14 @@ void de_emp(
 
 \*---------------------------------------------------------------------------*/
 
-void hanning_window(
-  float Sn[],	/* input frame of speech samples */
-  float Wn[],	/* output frame of windowed samples */
-  int Nsam	/* number of samples */
-)
-{
-  int i;	/* loop variable */
+void hanning_window(float Sn[], /* input frame of speech samples */
+                    float Wn[], /* output frame of windowed samples */
+                    int Nsam    /* number of samples */
+) {
+  int i; /* loop variable */
 
-  for(i=0; i<Nsam; i++)
-    Wn[i] = Sn[i]*(0.5 - 0.5*cosf(2*PI*(float)i/(Nsam-1)));
+  for (i = 0; i < Nsam; i++)
+    Wn[i] = Sn[i] * (0.5 - 0.5 * cosf(2 * PI * (float)i / (Nsam - 1)));
 }
 
 /*---------------------------------------------------------------------------*\
@@ -119,19 +111,16 @@ void hanning_window(
 
 \*---------------------------------------------------------------------------*/
 
-void autocorrelate(
-  float Sn[],	/* frame of Nsam windowed speech samples */
-  float Rn[],	/* array of P+1 autocorrelation coefficients */
-  int Nsam,	/* number of windowed samples to use */
-  int order	/* order of LPC analysis */
-)
-{
-  int i,j;	/* loop variables */
+void autocorrelate(float Sn[], /* frame of Nsam windowed speech samples */
+                   float Rn[], /* array of P+1 autocorrelation coefficients */
+                   int Nsam,   /* number of windowed samples to use */
+                   int order   /* order of LPC analysis */
+) {
+  int i, j; /* loop variables */
 
-  for(j=0; j<order+1; j++) {
+  for (j = 0; j < order + 1; j++) {
     Rn[j] = 0.0;
-    for(i=0; i<Nsam-j; i++)
-      Rn[j] += Sn[i]*Sn[i+j];
+    for (i = 0; i < Nsam - j; i++) Rn[j] += Sn[i] * Sn[i + j];
   }
 }
 
@@ -150,36 +139,31 @@ void autocorrelate(
 
 \*---------------------------------------------------------------------------*/
 
-void levinson_durbin(
-  float R[],		/* order+1 autocorrelation coeff */
-  float lpcs[],		/* order+1 LPC's */
-  int order		/* order of the LPC analysis */
-)
-{
-  float a[order+1][order+1];
+void levinson_durbin(float R[],    /* order+1 autocorrelation coeff */
+                     float lpcs[], /* order+1 LPC's */
+                     int order     /* order of the LPC analysis */
+) {
+  float a[order + 1][order + 1];
   float sum, e, k;
-  int i,j;				/* loop variables */
+  int i, j; /* loop variables */
 
-  e = R[0];				/* Equation 38a, Makhoul */
+  e = R[0]; /* Equation 38a, Makhoul */
 
-  for(i=1; i<=order; i++) {
+  for (i = 1; i <= order; i++) {
     sum = 0.0;
-    for(j=1; j<=i-1; j++)
-      sum += a[i-1][j]*R[i-j];
-    k = -1.0*(R[i] + sum)/e;		/* Equation 38b, Makhoul */
-    if (fabsf(k) > 1.0)
-      k = 0.0;
+    for (j = 1; j <= i - 1; j++) sum += a[i - 1][j] * R[i - j];
+    k = -1.0 * (R[i] + sum) / e; /* Equation 38b, Makhoul */
+    if (fabsf(k) > 1.0) k = 0.0;
 
     a[i][i] = k;
 
-    for(j=1; j<=i-1; j++)
-      a[i][j] = a[i-1][j] + k*a[i-1][i-j];	/* Equation 38c, Makhoul */
+    for (j = 1; j <= i - 1; j++)
+      a[i][j] = a[i - 1][j] + k * a[i - 1][i - j]; /* Equation 38c, Makhoul */
 
-    e *= (1-k*k);				/* Equation 38d, Makhoul */
+    e *= (1 - k * k); /* Equation 38d, Makhoul */
   }
 
-  for(i=1; i<=order; i++)
-    lpcs[i] = a[order][i];
+  for (i = 1; i <= order; i++) lpcs[i] = a[order][i];
   lpcs[0] = 1.0;
 }
 
@@ -194,20 +178,17 @@ void levinson_durbin(
 
 \*---------------------------------------------------------------------------*/
 
-void inverse_filter(
-  float Sn[],	/* Nsam input samples */
-  float a[],	/* LPCs for this frame of samples */
-  int Nsam,	/* number of samples */
-  float res[],	/* Nsam residual samples */
-  int order	/* order of LPC */
-)
-{
-  int i,j;	/* loop variables */
-
-  for(i=0; i<Nsam; i++) {
+void inverse_filter(float Sn[],  /* Nsam input samples */
+                    float a[],   /* LPCs for this frame of samples */
+                    int Nsam,    /* number of samples */
+                    float res[], /* Nsam residual samples */
+                    int order    /* order of LPC */
+) {
+  int i, j; /* loop variables */
+
+  for (i = 0; i < Nsam; i++) {
     res[i] = 0.0;
-    for(j=0; j<=order; j++)
-      res[i] += Sn[i-j]*a[j];
+    for (j = 0; j <= order; j++) res[i] += Sn[i - j] * a[j];
   }
 }
 
@@ -223,7 +204,7 @@ void inverse_filter(
  The synthesis filter has memory as well, this is treated in the same way
  as the memory for the inverse filter (see inverse_filter() notes above).
  The difference is that the memory for the synthesis filter is stored in
- the output array, wheras the memory of the inverse filter is stored in the
+ the output array, whereas the memory of the inverse filter is stored in the
  input array.
 
  Note: the calling function must update the filter memory.
@@ -231,21 +212,19 @@ void inverse_filter(
 \*---------------------------------------------------------------------------*/
 
 void synthesis_filter(
-  float res[],	/* Nsam input residual (excitation) samples */
-  float a[],	/* LPCs for this frame of speech samples */
-  int Nsam,	/* number of speech samples */
-  int order,	/* LPC order */
-  float Sn_[]	/* Nsam output synthesised speech samples */
-)
-{
-  int i,j;	/* loop variables */
+    float res[], /* Nsam input residual (excitation) samples */
+    float a[],   /* LPCs for this frame of speech samples */
+    int Nsam,    /* number of speech samples */
+    int order,   /* LPC order */
+    float Sn_[]  /* Nsam output synthesised speech samples */
+) {
+  int i, j; /* loop variables */
 
   /* Filter Nsam samples */
 
-  for(i=0; i<Nsam; i++) {
-    Sn_[i] = res[i]*a[0];
-    for(j=1; j<=order; j++)
-      Sn_[i] -= Sn_[i-j]*a[j];
+  for (i = 0; i < Nsam; i++) {
+    Sn_[i] = res[i] * a[0];
+    for (j = 1; j <= order; j++) Sn_[i] -= Sn_[i - j] * a[j];
   }
 }
 
@@ -258,29 +237,25 @@ void synthesis_filter(
 
 \*---------------------------------------------------------------------------*/
 
-void find_aks(
-  float Sn[],	/* Nsam samples with order sample memory */
-  float a[],	/* order+1 LPCs with first coeff 1.0 */
-  int Nsam,	/* number of input speech samples */
-  int order,	/* order of the LPC analysis */
-  float *E	/* residual energy */
-)
-{
-  float Wn[LPC_MAX_N];	/* windowed frame of Nsam speech samples */
-  float R[order+1];	/* order+1 autocorrelation values of Sn[] */
+void find_aks(float Sn[], /* Nsam samples with order sample memory */
+              float a[],  /* order+1 LPCs with first coeff 1.0 */
+              int Nsam,   /* number of input speech samples */
+              int order,  /* order of the LPC analysis */
+              float *E    /* residual energy */
+) {
+  float Wn[LPC_MAX_N]; /* windowed frame of Nsam speech samples */
+  float R[order + 1];  /* order+1 autocorrelation values of Sn[] */
   int i;
 
   assert(Nsam < LPC_MAX_N);
 
-  hanning_window(Sn,Wn,Nsam);
-  autocorrelate(Wn,R,Nsam,order);
-  levinson_durbin(R,a,order);
+  hanning_window(Sn, Wn, Nsam);
+  autocorrelate(Wn, R, Nsam, order);
+  levinson_durbin(R, a, order);
 
   *E = 0.0;
-  for(i=0; i<=order; i++)
-    *E += a[i]*R[i];
-  if (*E < 0.0)
-    *E = 1E-12;
+  for (i = 0; i <= order; i++) *E += a[i] * R[i];
+  if (*E < 0.0) *E = 1E-12;
 }
 
 /*---------------------------------------------------------------------------*\
@@ -291,16 +266,12 @@ void find_aks(
 
 \*---------------------------------------------------------------------------*/
 
-void weight(
-  float ak[],	/* vector of order+1 LPCs */
-  float gamma,	/* weighting factor */
-  int order,	/* num LPCs (excluding leading 1.0) */
-  float akw[]	/* weighted vector of order+1 LPCs */
-)
-{
+void weight(float ak[],  /* vector of order+1 LPCs */
+            float gamma, /* weighting factor */
+            int order,   /* num LPCs (excluding leading 1.0) */
+            float akw[]  /* weighted vector of order+1 LPCs */
+) {
   int i;
 
-  for(i=1; i<=order; i++)
-    akw[i] = ak[i]*powf(gamma,(float)i);
+  for (i = 1; i <= order; i++) akw[i] = ak[i] * powf(gamma, (float)i);
 }
-
-- 
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