added output level scaling

psrdada_cpp/effelsberg/edd/FftSpectrometer.cuh

@@ -29,6 +29,7 @@ public:
         std::size_t naccumulate,
         std::size_t nbits,
         float input_level,
+        float output_level,
         HandlerType& handler);
     ~FftSpectrometer();
 
@@ -62,7 +63,6 @@ private:
     std::size_t _fft_length;
     std::size_t _naccumulate;
     std::size_t _nbits;
-    float _input_level;
     HandlerType& _handler;
     cufftHandle _fft_plan;
     int _nchans;

psrdada_cpp/effelsberg/edd/detail/FftSpectrometer.cu

@@ -15,12 +15,12 @@ FftSpectrometer<HandlerType>::FftSpectrometer(
     std::size_t naccumulate,
     std::size_t nbits,
     float input_level,
+    float output_level,
     HandlerType& handler)
     : _buffer_bytes(buffer_bytes)
     , _fft_length(fft_length)
     , _naccumulate(naccumulate)
     , _nbits(nbits)
-    , _input_level(input_level)
     , _handler(handler)
     , _fft_plan(0)
     , _call_count(0)
@@ -38,9 +38,9 @@ FftSpectrometer<HandlerType>::FftSpectrometer(
     int batch = nsamps_per_buffer/_fft_length;
     BOOST_LOG_TRIVIAL(debug) << "Calculating scales and offsets";
     float dof = 2 * _naccumulate;
-    float scale = std::pow(_input_level * std::sqrt(static_cast<float>(_nchans)), 2);
+    float scale = std::pow(input_level * std::sqrt(static_cast<float>(_nchans)), 2);
     float offset = scale * dof;
-    float scaling = scale * std::sqrt(2 * dof);
+    float scaling = scale * std::sqrt(2 * dof) / output_level;
     BOOST_LOG_TRIVIAL(debug) << "Correction factors for 8-bit conversion: offset = " << offset << ", scaling = " << scaling;
     BOOST_LOG_TRIVIAL(debug) << "Generating FFT plan";
     int n[] = {static_cast<int>(_fft_length)};

psrdada_cpp/effelsberg/edd/src/fft_spectrometer_cli.cu

@@ -30,6 +30,7 @@ int main(int argc, char** argv)
         int naccumulate;
         int nbits;
         float input_level;
+        float output_level;
         std::time_t now = std::time(NULL);
         std::tm * ptm = std::localtime(&now);
         char buffer[32];
@@ -63,6 +64,9 @@ int main(int argc, char** argv)
         ("input_level", po::value<float>(&input_level)->required(),
             "The input power level (standard deviation, used for 8-bit conversion)")
 
+        ("output_level", po::value<float>(&output_level)->required(),
+            "The output power level (standard deviation, used for 8-bit conversion)")
+
         ("outfile,o", po::value<std::string>(&filename)
             ->default_value(filename),
             "The output file to write spectra to")
@@ -101,7 +105,7 @@ int main(int argc, char** argv)
         std::size_t buffer_bytes = client.data_buffer_size();
         SimpleFileWriter sink(filename);
         //NullSink sink;
-        effelsberg::edd::FftSpectrometer<decltype(sink)> spectrometer(buffer_bytes, fft_length, naccumulate, nbits, input_level, sink);
+        effelsberg::edd::FftSpectrometer<decltype(sink)> spectrometer(buffer_bytes, fft_length, naccumulate, nbits, input_level, output_level, sink);
         DadaInputStream<decltype(spectrometer)> istream(input_key, log, spectrometer);
         istream.start();
         /**

psrdada_cpp/effelsberg/edd/test/src/FftSpectrometerTester.cu

@@ -42,7 +42,7 @@ void FftSpectrometerTester::performance_test(
     std::vector<char> header_block(4096);
     RawBytes header_raw_bytes(header_block.data(), 4096, 4096);
     NullSink null_sink;
-    FftSpectrometer<NullSink> spectrometer(input_block_bytes, fft_length, tscrunch, nbits, 16.0f, null_sink);
+    FftSpectrometer<NullSink> spectrometer(input_block_bytes, fft_length, tscrunch, nbits, 16.0f, 16.0f, null_sink);
     spectrometer.init(header_raw_bytes);
     for (int ii = 0; ii < 100; ++ii)
     {