Add normalisation for file output

2 files changed, 22 insertions, 5 deletions

diff --git a/doc/example.ini b/doc/example.ini
index 0659813..f8cec36 100644
--- a/doc/example.ini
+++ b/doc/example.ini
@@ -141,13 +141,16 @@ output=uhd
 
 [fileoutput]
 ; Two output formats are supported: In the default mode,
-; the file output writes I/Q float values (i.e. complex float)
-; to the file. The I and Q samples can take values up to
-; 100000 in absolute magnitude with gainmode FIX.
-; With gainmode VAR, they should never exceed 50000.
-; With gainmode MAX, thet are limited to 32767.
+; the file output writes I/Q float values (i.e. complex
+; float) to the file. The I and Q samples can take values up
+; to 810000 in absolute magnitude with gainmode FIX. With
+; gainmode VAR and FIX, they should never exceed 50000.
 ;format=complexf
 ;
+; When the format is set to complexf_normalised the maximal
+; amplitude written to a file, is the digital gain +-10%.
+;format=complexf_normalised
+;
 ; When the format is set to s8, the output writes I/Q 8-bit
 ; signed integers, where the magnitude is multiplied by 128/50000
 ; effectively mapping the gainmode VAR range of -50000 -- 50000
diff --git a/src/DabMod.cpp b/src/DabMod.cpp
index 301b078..4e4cdab 100644
--- a/src/DabMod.cpp
+++ b/src/DabMod.cpp
@@ -81,6 +81,11 @@
  */
 static const float normalise_factor = 50000.0f;
 
+//Empirical normalisation factors used to normalise the samples to amplitude 1.
+static const float normalise_factor_file_fix = 81000.0f;
+static const float normalise_factor_file_var = 46000.0f;
+static const float normalise_factor_file_max = 46000.0f;
+
 typedef std::complex<float> complexf;
 
 using namespace std;
@@ -183,6 +188,15 @@ static shared_ptr<ModOutput> prepare_output(
         if (s.fileOutputFormat == "complexf") {
             output = make_shared<OutputFile>(s.outputName);
         }
+        if (s.fileOutputFormat == "complexf_normalised") {
+            if (s.gainMode == GainMode::GAIN_FIX)
+                s.normalise = 1.0 / normalise_factor_file_fix;
+            else if (s.gainMode == GainMode::GAIN_MAX)
+                s.normalise = 1.0 / normalise_factor_file_max;
+            else if (s.gainMode == GainMode::GAIN_VAR)
+                s.normalise = 1.0 / normalise_factor_file_var;
+            output = make_shared<OutputFile>(s.outputName);
+        }
         else if (s.fileOutputFormat == "s8") {
             // We must normalise the samples to the interval [-127.0; 127.0]
             s.normalise = 127.0f / normalise_factor;