From f40d030e2ef3c3f85673cf9382e3d579269fc3a4 Mon Sep 17 00:00:00 2001
From: f4exb <f4exb06@gmail.com>
Date: Wed, 15 Mar 2017 15:37:51 +0100
Subject: [PATCH] FFT filter: SSB filter leave DC component by default in both
 USB and LSB. Option to remove DC in both

---
 sdrbase/dsp/fftfilt.cxx | 15 +++++++++++----
 sdrbase/dsp/fftfilt.h   |  2 +-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/sdrbase/dsp/fftfilt.cxx b/sdrbase/dsp/fftfilt.cxx
index 5a7ea33ac..f11776b53 100644
--- a/sdrbase/dsp/fftfilt.cxx
+++ b/sdrbase/dsp/fftfilt.cxx
@@ -199,7 +199,7 @@ int fftfilt::runFilt(const cmplx & in, cmplx **out)
 }
 
 // Second version for single sideband
-int fftfilt::runSSB(const cmplx & in, cmplx **out, bool usb)
+int fftfilt::runSSB(const cmplx & in, cmplx **out, bool usb, bool getDC)
 {
 	data[inptr++] = in;
 	if (inptr < flen2)
@@ -208,17 +208,24 @@ int fftfilt::runSSB(const cmplx & in, cmplx **out, bool usb)
 
 	fft->ComplexFFT(data);
 
+	// get or reject DC component
+	data[0] = getDC ? data[0]*filter[0] : 0;
+
 	// Discard frequencies for ssb
-	if ( usb )
-		for (int i = 0; i < flen2; i++) {
+	if (usb)
+	{
+		for (int i = 1; i < flen2; i++) {
 			data[i] *= filter[i];
 			data[flen2 + i] = 0;
 		}
+	}
 	else
-		for (int i = 0; i < flen2; i++) {
+	{
+		for (int i = 1; i < flen2; i++) {
 			data[i] = 0;
 			data[flen2 + i] *= filter[flen2 + i];
 		}
+	}
 
 	// in-place FFT: freqdata overwritten with filtered timedata
 	fft->InverseComplexFFT(data);
diff --git a/sdrbase/dsp/fftfilt.h b/sdrbase/dsp/fftfilt.h
index 4af4613fb..903bb5b46 100644
--- a/sdrbase/dsp/fftfilt.h
+++ b/sdrbase/dsp/fftfilt.h
@@ -26,7 +26,7 @@ public:
 
 	int noFilt(const cmplx& in, cmplx **out);
 	int runFilt(const cmplx& in, cmplx **out);
-	int runSSB(const cmplx& in, cmplx **out, bool usb);
+	int runSSB(const cmplx& in, cmplx **out, bool usb, bool getDC = true);
 	int runDSB(const cmplx& in, cmplx **out);
 
 protected: