Add OFDM windowing to config file

4 files changed, 16 insertions, 2 deletions

diff --git a/doc/example.ini b/doc/example.ini
index cf56720..d356ee1 100644
--- a/doc/example.ini
+++ b/doc/example.ini
@@ -128,6 +128,13 @@ rate=2048000
 ; and
 ;dac_clk_rate=128000000
 
+; When nonzero, overlap ofdmwindowing samples from each OFDM symbol
+; onto the previous and next symbol, using a raised cosine window function.
+; This has the effect of smoothing the transition from one symbol to the next,
+; which improves spectrum shape.
+; In Transmission Mode I, every data symbol is composed of 2552 samples.
+;ofdmwindowing=10
+
 ; Settings for crest factor reduction. Statistics for ratio of
 ; samples that were clipped are available through the RC.
 [cfr]
diff --git a/src/ConfigParser.cpp b/src/ConfigParser.cpp
index 1cc94c0..2c93a57 100644
--- a/src/ConfigParser.cpp
+++ b/src/ConfigParser.cpp
@@ -159,8 +159,12 @@ static void parse_configfile(
 
     mod_settings.dabMode = pt.get("modulator.mode", mod_settings.dabMode);
     mod_settings.clockRate = pt.get("modulator.dac_clk_rate", (size_t)0);
-    mod_settings.digitalgain = pt.get("modulator.digital_gain", mod_settings.digitalgain);
+    mod_settings.digitalgain = pt.get("modulator.digital_gain",
+            mod_settings.digitalgain);
+
     mod_settings.outputRate = pt.get("modulator.rate", mod_settings.outputRate);
+    mod_settings.ofdmWindowOverlap = pt.get("modulator.ofdmwindowing",
+            mod_settings.ofdmWindowOverlap);
 
     // FIR Filter parameters:
     if (pt.get("firfilter.enabled", 0) == 1) {
diff --git a/src/ConfigParser.h b/src/ConfigParser.h
index a8d7837..0be3558 100644
--- a/src/ConfigParser.h
+++ b/src/ConfigParser.h
@@ -82,6 +82,8 @@ struct mod_settings_t {
     float cfrClip = 1.0f;
     float cfrErrorClip = 1.0f;
 
+    // Settings for the OFDM windowing
+    unsigned ofdmWindowOverlap = 0;
 
 #if defined(HAVE_OUTPUT_UHD)
     OutputUHDConfig outputuhd_conf;
diff --git a/src/DabModulator.cpp b/src/DabModulator.cpp
index cded280..0818f4f 100644
--- a/src/DabModulator.cpp
+++ b/src/DabModulator.cpp
@@ -201,7 +201,8 @@ int DabModulator::process(Buffer* dataOut)
         rcs.enrol(cifGain.get());
 
         auto cifGuard = make_shared<GuardIntervalInserter>(
-                myNbSymbols, mySpacing, myNullSize, mySymSize);
+                myNbSymbols, mySpacing, myNullSize, mySymSize,
+                m_settings.ofdmWindowOverlap);
         rcs.enrol(cifGuard.get());
 
         shared_ptr<FIRFilter> cifFilter;