From 0a83f5082138877ed2d6a506b4fdc334d06150d7 Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Wed, 18 May 2022 22:21:12 +0200
Subject: [PATCH] Added Blackman-Harris 7 term FFT window

---
 .../demodchirpchat/chirpchatdemodgui.ui       |  5 ++++
 plugins/channelrx/demodssb/ssbdemodgui.ui     |  5 ++++
 .../channelrx/demodssb/ssbdemodsettings.cpp   |  3 ++-
 sdrbase/dsp/fftwindow.cpp                     |  4 +++
 sdrbase/dsp/fftwindow.h                       | 27 +++++++++++++++----
 sdrgui/gui/glspectrumgui.ui                   |  5 ++++
 6 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/plugins/channelrx/demodchirpchat/chirpchatdemodgui.ui b/plugins/channelrx/demodchirpchat/chirpchatdemodgui.ui
index 8c14b944e..d3e938fcc 100644
--- a/plugins/channelrx/demodchirpchat/chirpchatdemodgui.ui
+++ b/plugins/channelrx/demodchirpchat/chirpchatdemodgui.ui
@@ -336,6 +336,11 @@
           <string>Black</string>
          </property>
         </item>
+        <item>
+         <property name="text">
+          <string>B-H7</string>
+         </property>
+        </item>
        </widget>
       </item>
       <item>
diff --git a/plugins/channelrx/demodssb/ssbdemodgui.ui b/plugins/channelrx/demodssb/ssbdemodgui.ui
index b82c8f2d6..c14f736e7 100644
--- a/plugins/channelrx/demodssb/ssbdemodgui.ui
+++ b/plugins/channelrx/demodssb/ssbdemodgui.ui
@@ -415,6 +415,11 @@
           <string>Black</string>
          </property>
         </item>
+        <item>
+         <property name="text">
+          <string>B-H7</string>
+         </property>
+        </item>
        </widget>
       </item>
       <item>
diff --git a/plugins/channelrx/demodssb/ssbdemodsettings.cpp b/plugins/channelrx/demodssb/ssbdemodsettings.cpp
index ebe321025..c6837a864 100644
--- a/plugins/channelrx/demodssb/ssbdemodsettings.cpp
+++ b/plugins/channelrx/demodssb/ssbdemodsettings.cpp
@@ -188,7 +188,8 @@ bool SSBDemodSettings::deserialize(const QByteArray& data)
             d.readS32(102+ 10*i, &tmp, 3);
             m_filterBank[i].m_lowCutoff = tmp * 100.0;
             d.readS32(103 + 10*i, &tmp, (int) FFTWindow::Blackman);
-            m_filterBank[i].m_fftWindow = (FFTWindow::Function) (tmp < 0 ? 0 : tmp > (int) FFTWindow::Blackman ? (int) FFTWindow::Blackman : tmp);
+            m_filterBank[i].m_fftWindow =
+                (FFTWindow::Function) (tmp < 0 ? 0 : tmp > (int) FFTWindow::BlackmanHarris7 ? (int) FFTWindow::BlackmanHarris7 : tmp);
         }
 
         return true;
diff --git a/sdrbase/dsp/fftwindow.cpp b/sdrbase/dsp/fftwindow.cpp
index 3ded5e75f..a1cfe4f4a 100644
--- a/sdrbase/dsp/fftwindow.cpp
+++ b/sdrbase/dsp/fftwindow.cpp
@@ -76,6 +76,10 @@ void FFTWindow::create(Function function, int n)
             wFunc = blackman;
             break;
 
+        case BlackmanHarris7:
+            wFunc = blackmanHarris7;
+            break;
+
 		case Rectangle:
 		default:
 			wFunc = rectangle;
diff --git a/sdrbase/dsp/fftwindow.h b/sdrbase/dsp/fftwindow.h
index a64dc3337..b543aa39d 100644
--- a/sdrbase/dsp/fftwindow.h
+++ b/sdrbase/dsp/fftwindow.h
@@ -34,7 +34,8 @@ public:
 		Hanning,
 		Rectangle,
 		Kaiser,
-        Blackman
+        Blackman,
+        BlackmanHarris7
 	};
 
 	FFTWindow();
@@ -65,15 +66,31 @@ private:
 		return (2.0 / (n - 1.0)) * ( (n - 1.0) / 2.0 - fabs(i - (n - 1.0) / 2.0)) * 2.0;
 	}
 
-	static inline Real blackmanHarris(Real n, Real i)
+	static inline Real blackmanHarris(Real n, Real i) // 4 term Blackman-Harris
 	{
 		// amplitude correction = 2.79
-		return (0.35875 - 0.48829 * cos((2.0 * M_PI * i) / n) + 0.14128 * cos((4.0 * M_PI * i) / n) - 0.01168 * cos((6.0 * M_PI * i) / n)) * 2.79;
+		return (0.35875
+            - 0.48829 * cos((2.0 * M_PI * i) / n)
+            + 0.14128 * cos((4.0 * M_PI * i) / n)
+            - 0.01168 * cos((6.0 * M_PI * i) / n)) * 2.79;
 	}
 
-    static inline Real blackman(Real n, Real i)
+	static inline Real blackmanHarris7(Real n, Real i) // 7 term Blackman-Harris
+	{
+		return (0.27105
+            - 0.43330 * cos((2.0 * M_PI * i) / n)
+            + 0.21812 * cos((4.0 * M_PI * i) / n)
+            - 0.065925 * cos((6.0 * M_PI * i) / n)
+            + 0.010812 * cos((8.0 * M_PI * i) / n)
+            - 0.00077658 * cos((10.0 * M_PI * i) / n)
+            + 0.000013887 * cos((12.0 * M_PI * i) / n)) * 3.72;
+	}
+
+    static inline Real blackman(Real n, Real i) // 3 term Blackman
     {
-        return (0.42438 - 0.49734 * cos(2.0 * M_PI * i / n) + 0.078279 * cos(4.0 * M_PI * i / n)) * 2.37;
+        return (0.42438
+            - 0.49734 * cos(2.0 * M_PI * i / n)
+            + 0.078279 * cos(4.0 * M_PI * i / n)) * 2.37;
     }
 
 	static inline Real hamming(Real n, Real i)
diff --git a/sdrgui/gui/glspectrumgui.ui b/sdrgui/gui/glspectrumgui.ui
index d676195b8..788f65f99 100644
--- a/sdrgui/gui/glspectrumgui.ui
+++ b/sdrgui/gui/glspectrumgui.ui
@@ -106,6 +106,11 @@
          <string>Black</string>
         </property>
        </item>
+       <item>
+        <property name="text">
+         <string>B-H7</string>
+        </property>
+       </item>
       </widget>
      </item>
      <item>