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-rw-r--r--doc/example.ini11
-rw-r--r--src/ConfigParser.cpp7
-rw-r--r--src/ConfigParser.h6
-rw-r--r--src/DabModulator.cpp9
-rw-r--r--src/OfdmGenerator.cpp73
-rw-r--r--src/OfdmGenerator.h12
6 files changed, 87 insertions, 31 deletions
diff --git a/doc/example.ini b/doc/example.ini
index 425dfa4..512e196 100644
--- a/doc/example.ini
+++ b/doc/example.ini
@@ -127,6 +127,17 @@ dac_clk_rate=0
; and
;dac_clk_rate=128000000
+; Settings for crest factor reduction
+[cfr]
+enable=0
+
+; At what amplitude the signal should be clipped
+clip=1.0
+
+; How much to clip the error signal used to compensate the effect
+; of clipping
+error_clip=1.0
+
[firfilter]
; The FIR Filter can be used to create a better spectral quality.
enabled=1
diff --git a/src/ConfigParser.cpp b/src/ConfigParser.cpp
index 9ac1280..1cc94c0 100644
--- a/src/ConfigParser.cpp
+++ b/src/ConfigParser.cpp
@@ -177,6 +177,13 @@ static void parse_configfile(
pt.get<int>("poly.num_threads", 0);
}
+ // Crest factor reduction
+ if (pt.get("cfr.enabled", 0) == 1) {
+ mod_settings.enableCfr = true;
+ mod_settings.cfrClip = pt.get<float>("cfr.clip");
+ mod_settings.cfrErrorClip = pt.get<float>("cfr.error_clip");
+ }
+
// Output options
std::string output_selected;
try {
diff --git a/src/ConfigParser.h b/src/ConfigParser.h
index 89f0fb7..a8d7837 100644
--- a/src/ConfigParser.h
+++ b/src/ConfigParser.h
@@ -77,6 +77,12 @@ struct mod_settings_t {
std::string polyCoefFilename = "";
unsigned polyNumThreads = 0;
+ // Settings for crest factor reduction
+ bool enableCfr = false;
+ float cfrClip = 1.0f;
+ float cfrErrorClip = 1.0f;
+
+
#if defined(HAVE_OUTPUT_UHD)
OutputUHDConfig outputuhd_conf;
#endif
diff --git a/src/DabModulator.cpp b/src/DabModulator.cpp
index cc2642a..0914469 100644
--- a/src/DabModulator.cpp
+++ b/src/DabModulator.cpp
@@ -183,7 +183,14 @@ int DabModulator::process(Buffer* dataOut)
}
auto cifOfdm = make_shared<OfdmGenerator>(
- (1 + myNbSymbols), myNbCarriers, mySpacing);
+ (1 + myNbSymbols),
+ myNbCarriers,
+ mySpacing,
+ m_settings.enableCfr,
+ m_settings.cfrClip,
+ m_settings.cfrErrorClip);
+
+ rcs.enrol(cifOfdm.get());
auto cifGain = make_shared<GainControl>(
mySpacing,
diff --git a/src/OfdmGenerator.cpp b/src/OfdmGenerator.cpp
index 3d3dfd7..41c1c85 100644
--- a/src/OfdmGenerator.cpp
+++ b/src/OfdmGenerator.cpp
@@ -26,6 +26,8 @@
#include "OfdmGenerator.h"
#include "PcDebug.h"
+
+#include <complex>
#include "fftw3.h"
#define FFT_TYPE fftwf_complex
@@ -33,23 +35,25 @@
#include <string.h>
#include <stdexcept>
#include <assert.h>
-#include <complex>
#include <string>
OfdmGenerator::OfdmGenerator(size_t nbSymbols,
- size_t nbCarriers,
- size_t spacing,
- bool inverse) :
+ size_t nbCarriers,
+ size_t spacing,
+ bool enableCfr,
+ float cfrClip,
+ float cfrErrorClip,
+ bool inverse) :
ModCodec(), RemoteControllable("ofdm"),
myFftPlan(nullptr),
myFftIn(nullptr), myFftOut(nullptr),
myNbSymbols(nbSymbols),
myNbCarriers(nbCarriers),
mySpacing(spacing),
- myCfr(false),
- myCfrClip(1.0f),
- myCfrErrorClip(1.0f),
+ myCfr(enableCfr),
+ myCfrClip(cfrClip),
+ myCfrErrorClip(cfrErrorClip),
myCfrFft(nullptr)
{
PDEBUG("OfdmGenerator::OfdmGenerator(%zu, %zu, %zu, %s) @ %p\n",
@@ -62,8 +66,8 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols,
/* register the parameters that can be remote controlled */
RC_ADD_PARAMETER(cfr, "Enable crest factor reduction");
- RC_ADD_PARAMETER(cfrclip, "CFR: Clip to amplitude");
- RC_ADD_PARAMETER(cfrerrorclip, "CFR: Limit error");
+ RC_ADD_PARAMETER(clip, "CFR: Clip to amplitude");
+ RC_ADD_PARAMETER(errorclip, "CFR: Limit error");
if (inverse) {
myPosDst = (nbCarriers & 1 ? 0 : 1);
@@ -100,11 +104,10 @@ OfdmGenerator::OfdmGenerator(size_t nbSymbols,
myFftIn, myFftOut,
FFTW_BACKWARD, FFTW_MEASURE);
- myCfrPostClip.resize(N);
- myCfrPostFft.resize(N);
+ myCfrPostClip = (FFT_TYPE*)fftwf_malloc(sizeof(FFT_TYPE) * N);
+ myCfrPostFft = (FFT_TYPE*)fftwf_malloc(sizeof(FFT_TYPE) * N);
myCfrFft = fftwf_plan_dft_1d(N,
- reinterpret_cast<FFT_TYPE*>(myCfrPostClip.data()),
- reinterpret_cast<FFT_TYPE*>(myCfrPostFft.data()),
+ myCfrPostClip, myCfrPostFft,
FFTW_FORWARD, FFTW_MEASURE);
if (sizeof(complexf) != sizeof(FFT_TYPE)) {
@@ -167,6 +170,9 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
"OfdmGenerator::process output size not valid!");
}
+ myNumClip = 0;
+ myNumErrorClip = 0;
+
for (size_t i = 0; i < myNbSymbols; ++i) {
myFftIn[0][0] = 0;
myFftIn[0][1] = 0;
@@ -177,10 +183,17 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
memcpy(&myFftIn[myNegDst], &in[myNegSrc],
myNegSize * sizeof(FFT_TYPE));
+ std::vector<complexf> reference;
+ if (myCfr) {
+ reference.resize(mySpacing);
+ memcpy(reference.data(), myFftIn, mySpacing * sizeof(FFT_TYPE));
+ }
+
fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut
if (myCfr) {
- cfr_one_iteration(dataOut, i);
+ complexf *symbol = reinterpret_cast<complexf*>(myFftOut);
+ cfr_one_iteration(symbol, reference.data());
}
memcpy(out, myFftOut, mySpacing * sizeof(FFT_TYPE));
@@ -188,33 +201,36 @@ int OfdmGenerator::process(Buffer* const dataIn, Buffer* dataOut)
in += myNbCarriers;
out += mySpacing;
}
+
+ if (myCfr) {
+ etiLog.level(debug) << "CFR: " << myNumClip << " clipped, " <<
+ myNumErrorClip << " err clipped";
+ }
+
return sizeOut;
}
-void OfdmGenerator::cfr_one_iteration(Buffer *symbols, size_t symbol_ix)
+void OfdmGenerator::cfr_one_iteration(complexf *symbol, const complexf *reference)
{
- complexf* out = reinterpret_cast<complexf*>(symbols->getData());
-
- out += (symbol_ix * mySpacing);
-
// use std::norm instead of std::abs to avoid calculating the
// square roots
const float clip_squared = myCfrClip * myCfrClip;
// Clip
for (size_t i = 0; i < mySpacing; i++) {
- const float mag_squared = std::norm(out[i]);
+ const float mag_squared = std::norm(symbol[i]);
if (mag_squared > clip_squared) {
// normalise absolute value to myCfrClip:
// x_clipped = x * clip / |x|
// = x * sqrt(clip_squared) / sqrt(mag_squared)
// = x * sqrt(clip_squared / mag_squared)
- out[i] *= std::sqrt(clip_squared / mag_squared);
+ symbol[i] *= std::sqrt(clip_squared / mag_squared);
+ myNumClip++;
}
}
// Take FFT of our clipped signal
- std::copy(out, out + mySpacing, myCfrPostClip.begin());
+ memcpy(myCfrPostClip, symbol, mySpacing * sizeof(FFT_TYPE));
fftwf_execute(myCfrFft); // FFT from myCfrPostClip to myCfrPostFft
// Calculate the error in frequency domain by subtracting our reference
@@ -223,23 +239,26 @@ void OfdmGenerator::cfr_one_iteration(Buffer *symbols, size_t symbol_ix)
// extent.
const float err_clip_squared = myCfrErrorClip * myCfrErrorClip;
- complexf *reference = reinterpret_cast<complexf*>(myFftIn);
for (size_t i = 0; i < mySpacing; i++) {
- complexf error = myCfrPostFft[i] - reference[i];
+ const complexf constellation_point =
+ reinterpret_cast<complexf*>(myCfrPostFft)[i];
+
+ complexf error = reference[i] - constellation_point;
const float mag_squared = std::norm(error);
if (mag_squared > err_clip_squared) {
error *= std::sqrt(err_clip_squared / mag_squared);
+ myNumErrorClip++;
}
- // Update the reference in-place to avoid another copy for the
+ // Update the input to the FFT directl to avoid another copy for the
// subsequence IFFT
- reference[i] += error;
+ complexf *fft_in = reinterpret_cast<complexf*>(myFftIn);
+ fft_in[i] = constellation_point + error;
}
// Run our error-compensated symbol through the IFFT again
fftwf_execute(myFftPlan); // IFFT from myFftIn to myFftOut
-
}
diff --git a/src/OfdmGenerator.h b/src/OfdmGenerator.h
index 9a6fa01..a41d583 100644
--- a/src/OfdmGenerator.h
+++ b/src/OfdmGenerator.h
@@ -46,6 +46,9 @@ class OfdmGenerator : public ModCodec, public RemoteControllable
OfdmGenerator(size_t nbSymbols,
size_t nbCarriers,
size_t spacing,
+ bool enableCfr,
+ float cfrClip,
+ float cfrErrorClip,
bool inverse = true);
virtual ~OfdmGenerator();
OfdmGenerator(const OfdmGenerator&) = delete;
@@ -65,7 +68,7 @@ class OfdmGenerator : public ModCodec, public RemoteControllable
const std::string& parameter) const override;
protected:
- void cfr_one_iteration(Buffer *symbols, size_t symbol_ix);
+ void cfr_one_iteration(complexf *symbol, const complexf *reference);
fftwf_plan myFftPlan;
fftwf_complex *myFftIn, *myFftOut;
@@ -85,8 +88,11 @@ class OfdmGenerator : public ModCodec, public RemoteControllable
float myCfrClip;
float myCfrErrorClip;
fftwf_plan myCfrFft;
- std::vector<complexf> myCfrPostClip;
- std::vector<complexf> myCfrPostFft;
+ fftwf_complex *myCfrPostClip;
+ fftwf_complex *myCfrPostFft;
+
+ size_t myNumClip;
+ size_t myNumErrorClip;
};
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-25 07:03:00 +0000