From f799a68c9ce3f85f2c766aac6502466123c34ed3 Mon Sep 17 00:00:00 2001
From: TeaPoly <lekai.huang@gmail.com>
Date: Tue, 15 Feb 2022 17:19:17 +0800
Subject: [PATCH 1/2] Using modified pitch correlation from LPCNet

---
 src/pitch.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/pitch.cpp b/src/pitch.cpp
index 11a1a14..27024d6 100755
--- a/src/pitch.cpp
+++ b/src/pitch.cpp
@@ -382,7 +382,18 @@ void pitch_search(const opus_val16 *x_lp, opus_val16 *y,
       offset = 0;
    }
    *pitch = 2*best_pitch[0]-offset;
-   *pitch_corr = xcorr[best_pitch[0]];
+   /* *pitch_corr = xcorr[best_pitch[0]]; */
+   /* 
+      An estimate of the pitch correlation modified pitch correlation inspired by
+      section 3.1 Features and Quantization: Pitch in the paper 
+      <A Real-Time Wideband Neural Vocoder at 1.6 kb/s Using LPCNet
+
+      Link: https://jmvalin.ca/papers/lpcnet_codec.pdf
+    */
+   *pitch_corr = 2*xcorr[best_pitch[0]] / (
+      celt_inner_prod(x_lp4, x_lp4, len>>2)+
+      celt_inner_prod(&y_lp4[best_pitch[0]], &y_lp4[best_pitch[0]], len>>2)
+   );
 }
 
 #ifdef FIXED_POINT

From d9781ea012e59ef0a96ff5f93deb6ae8d1e0f673 Mon Sep 17 00:00:00 2001
From: TeaPoly <lekai.huang@gmail.com>
Date: Tue, 15 Feb 2022 17:35:26 +0800
Subject: [PATCH 2/2] Fix pitch correlation denominator

---
 src/pitch.cpp | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/src/pitch.cpp b/src/pitch.cpp
index 27024d6..6f9d646 100755
--- a/src/pitch.cpp
+++ b/src/pitch.cpp
@@ -365,6 +365,17 @@ void pitch_search(const opus_val16 *x_lp, opus_val16 *y,
 #endif
                    );
 
+   /* 
+      A modified pitch correlation inspired by section 3.1 Features and Quantization: Pitch 
+      in the paper <A Real-Time Wideband Neural Vocoder at 1.6 kb/s Using LPCNet>.
+
+      Link: https://jmvalin.ca/papers/lpcnet_codec.pdf
+    */
+   *pitch_corr = 2*xcorr[best_pitch[0]] / (
+      1+celt_inner_prod(x_lp, x_lp, len>>1)+
+      celt_inner_prod(&y[best_pitch[0]], &y[best_pitch[0]], len>>1)
+   );
+
    /* Refine by pseudo-interpolation */
    if (best_pitch[0]>0 && best_pitch[0]<(max_pitch>>1)-1)
    {
@@ -383,17 +394,6 @@ void pitch_search(const opus_val16 *x_lp, opus_val16 *y,
    }
    *pitch = 2*best_pitch[0]-offset;
    /* *pitch_corr = xcorr[best_pitch[0]]; */
-   /* 
-      An estimate of the pitch correlation modified pitch correlation inspired by
-      section 3.1 Features and Quantization: Pitch in the paper 
-      <A Real-Time Wideband Neural Vocoder at 1.6 kb/s Using LPCNet
-
-      Link: https://jmvalin.ca/papers/lpcnet_codec.pdf
-    */
-   *pitch_corr = 2*xcorr[best_pitch[0]] / (
-      celt_inner_prod(x_lp4, x_lp4, len>>2)+
-      celt_inner_prod(&y_lp4[best_pitch[0]], &y_lp4[best_pitch[0]], len>>2)
-   );
 }
 
 #ifdef FIXED_POINT