bugfix + improved NFM IF noise reduction (less distortion)

core/src/dsp/noise_reduction.h

@@ -65,6 +65,50 @@ namespace dsp {
             generic_block<FMIFNoiseReduction>::tempStart();
         }
 
+        void setTapCount(int tapCount) {
+            assert(generic_block<FMIFNoiseReduction>::_block_init);
+            std::lock_guard<std::mutex> lck(generic_block<FMIFNoiseReduction>::ctrlMtx);
+            generic_block<FMIFNoiseReduction>::tempStop();
+            generic_block<FMIFNoiseReduction>::unregisterInput(_in);
+
+            _tapCount = tapCount;
+
+            fftwf_destroy_plan(forwardPlan);
+            fftwf_destroy_plan(backwardPlan);
+            fftwf_free(delay);
+            fftwf_free(fft_in);
+            fftwf_free(fft_window);
+            fftwf_free(amp_buf);
+            fftwf_free(fft_cout);
+            fftwf_free(fft_fcout);
+
+            delay = (complex_t*)fftwf_malloc(sizeof(complex_t)*STREAM_BUFFER_SIZE);
+            fft_in = (complex_t*)fftwf_malloc(sizeof(complex_t)*_tapCount);
+            fft_window = (float*)fftwf_malloc(sizeof(float)*_tapCount);
+            amp_buf = (float*)fftwf_malloc(sizeof(float)*_tapCount);
+            fft_cout = (complex_t*)fftwf_malloc(sizeof(complex_t)*_tapCount);
+            fft_fcout = (complex_t*)fftwf_malloc(sizeof(complex_t)*_tapCount);
+            delay_start = &delay[_tapCount];
+
+            memset(delay, 0, sizeof(complex_t)*STREAM_BUFFER_SIZE);
+            memset(fft_in, 0, sizeof(complex_t)*_tapCount);
+            memset(amp_buf, 0, sizeof(float)*_tapCount);
+            memset(fft_cout, 0, sizeof(complex_t)*_tapCount);
+            memset(fft_fcout, 0, sizeof(complex_t)*_tapCount);
+            
+            for (int i = 0; i < _tapCount; i++) {
+                fft_window[i] = window_function::blackman(i, _tapCount - 1);
+            }
+
+            forwardPlan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_in, (fftwf_complex*)fft_cout, FFTW_FORWARD, FFTW_ESTIMATE);
+            backwardPlan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_cout, (fftwf_complex*)fft_fcout, FFTW_BACKWARD, FFTW_ESTIMATE);
+
+            spdlog::info("FM IF Noise reduction set to {0} taps", _tapCount);
+
+            generic_block<FMIFNoiseReduction>::registerInput(_in);
+            generic_block<FMIFNoiseReduction>::tempStart();
+        }
+
         void setLevel(float level) {
             _level = powf(10.0f, level / 10.0f);
         }

decoder_modules/radio/src/radio_module.h

@@ -384,6 +384,9 @@ private:
             vfo->setSampleRate(selectedDemod->getIFSampleRate(), bandwidth);
         }
 
+        // Configure bandwidth
+        setBandwidth(bandwidth);
+
         // Configure FM IF Noise Reduction
         setFMIFNREnabled(FMIFNRAllowed ? FMIFNREnabled : false);
 
@@ -395,6 +398,7 @@ private:
         setSquelchEnabled(squelchEnabled);
 
         // Configure noise blanker
+        fmnr.block.setTapCount((selectedDemod->getIFSampleRate() < 100000.0f) ? 8 : 32);
         nb.block.setLevel(nbLevel);
         setNoiseBlankerEnabled(nbEnabled);