From 5fd4ba805964783b18b2aab37f0efc4195b06f82 Mon Sep 17 00:00:00 2001
From: "Charles J. Cliffe" <cj@cubicproductions.com>
Date: Wed, 21 Oct 2015 19:50:53 -0400
Subject: [PATCH] Some DC-Spike removal magic..

Pay no attention to the spike behind the curtain.. <*|:-)
---
 src/AppFrame.cpp                        |  6 ++--
 src/process/SpectrumVisualProcessor.cpp | 42 +++++++++++++++++++++++++
 src/process/SpectrumVisualProcessor.h   |  2 ++
 src/sdr/SDRDeviceInfo.cpp               |  4 +--
 4 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/src/AppFrame.cpp b/src/AppFrame.cpp
index c4f6a30..a8560b1 100644
--- a/src/AppFrame.cpp
+++ b/src/AppFrame.cpp
@@ -786,7 +786,8 @@ void AppFrame::OnIdle(wxIdleEvent& event) {
 //    wxGetApp().getSpectrumDistributor()->run();
 
     SpectrumVisualProcessor *proc = wxGetApp().getSpectrumProcessor();
-    
+    proc->setHideDC(true);
+
     if (spectrumAvgMeter->inputChanged()) {
         float val = spectrumAvgMeter->getInputValue();
         if (val < 0.01) {
@@ -812,7 +813,8 @@ void AppFrame::OnIdle(wxIdleEvent& event) {
     dproc->setCenterFrequency(demodWaterfallCanvas->getCenterFrequency());
 
     SpectrumVisualProcessor *wproc = waterfallDataThread->getProcessor();
-
+    wproc->setHideDC(true);
+    
     if (waterfallSpeedMeter->inputChanged()) {
         float val = waterfallSpeedMeter->getInputValue();
         waterfallSpeedMeter->setLevel(val);
diff --git a/src/process/SpectrumVisualProcessor.cpp b/src/process/SpectrumVisualProcessor.cpp
index 8dc890d..8efd111 100644
--- a/src/process/SpectrumVisualProcessor.cpp
+++ b/src/process/SpectrumVisualProcessor.cpp
@@ -8,6 +8,7 @@ SpectrumVisualProcessor::SpectrumVisualProcessor() : lastInputBandwidth(0), last
     fftSize.store(0);
     centerFreq.store(0);
     bandwidth.store(0);
+    hideDC.store(false);
     
     freqShifter = nco_crcf_create(LIQUID_NCO);
     shiftFrequency = 0;
@@ -95,6 +96,11 @@ void SpectrumVisualProcessor::setup(int fftSize_in) {
     busy_run.unlock();
 }
 
+void SpectrumVisualProcessor::setHideDC(bool hideDC) {
+    this->hideDC.store(hideDC);
+}
+
+
 void SpectrumVisualProcessor::process() {
     if (!isOutputEmpty()) {
         return;
@@ -306,6 +312,42 @@ void SpectrumVisualProcessor::process() {
                 output->spectrum_points[i * 2] = ((float) i / (float) iMax);
                 output->spectrum_points[i * 2 + 1] = v;
             }
+                
+            if (hideDC.load()) { // DC-spike removal
+                long long freqMin = centerFreq-(bandwidth/2);
+                long long freqMax = centerFreq+(bandwidth/2);
+                long long zeroPt = (iqData->frequency-freqMin);
+                
+                if (freqMin < iqData->frequency && freqMax > iqData->frequency) {
+                    int freqRange = int(freqMax-freqMin);
+                    int freqStep = freqRange/fftSize;
+                    int fftStart = (zeroPt/freqStep)-(2000/freqStep);
+                    int fftEnd = (zeroPt/freqStep)+(2000/freqStep);
+                    
+//                    std::cout << "range:" << freqRange << ", step: " << freqStep << ", start: " << fftStart << ", end: " << fftEnd << std::endl;
+                    
+                    if (fftEnd-fftStart < 2) {
+                        fftEnd++;
+                        fftStart--;
+                    }
+                    
+                    int numSteps = (fftEnd-fftStart);
+                    int halfWay = fftStart+(numSteps/2);
+
+                    if ((fftEnd+numSteps/2+1 < fftSize) && (fftStart-numSteps/2-1 >= 0) && (fftEnd > fftStart)) {
+                        int n = 1;
+                        for (int i = fftStart; i < halfWay; i++) {
+                            output->spectrum_points[i * 2 + 1] = output->spectrum_points[(fftStart - n) * 2 + 1];
+                            n++;
+                        }
+                        n = 1;
+                        for (int i = halfWay; i < fftEnd; i++) {
+                            output->spectrum_points[i * 2 + 1] = output->spectrum_points[(fftEnd + n) * 2 + 1];
+                            n++;
+                        }
+                    }
+                }
+            }
             
             output->fft_ceiling = fft_ceil_maa;
             output->fft_floor = fft_floor_maa;
diff --git a/src/process/SpectrumVisualProcessor.h b/src/process/SpectrumVisualProcessor.h
index 6b7d079..38da510 100644
--- a/src/process/SpectrumVisualProcessor.h
+++ b/src/process/SpectrumVisualProcessor.h
@@ -33,6 +33,7 @@ public:
     int getDesiredInputSize();
     
     void setup(int fftSize);
+    void setHideDC(bool hideDC);
     
 protected:
     void process();
@@ -68,4 +69,5 @@ private:
     std::vector<liquid_float_complex> resampleBuffer;
     std::atomic_int desiredInputSize;
     std::mutex busy_run;
+    std::atomic_bool hideDC;
 };
diff --git a/src/sdr/SDRDeviceInfo.cpp b/src/sdr/SDRDeviceInfo.cpp
index 8111fc5..a0ad2b8 100644
--- a/src/sdr/SDRDeviceInfo.cpp
+++ b/src/sdr/SDRDeviceInfo.cpp
@@ -88,9 +88,9 @@ std::vector<long> &SDRDeviceChannel::getSampleRates() {
 long SDRDeviceChannel::getSampleRateNear(long sampleRate_in) {
     long returnRate = sampleRates[0];
     long sDelta = (long)sampleRate_in-sampleRates[0];
-    long minDelta = abs(sDelta);
+    long minDelta = std::abs(sDelta);
     for (std::vector<long>::iterator i = sampleRates.begin(); i != sampleRates.end(); i++) {
-        long thisDelta = abs(sampleRate_in - (*i));
+        long thisDelta = std::abs(sampleRate_in - (*i));
         if (thisDelta < minDelta) {
             minDelta = thisDelta;
             returnRate = (*i);