From aecd242b97c86d71afde033c0f91d0dc4c80da66 Mon Sep 17 00:00:00 2001
From: Kuba <132459354+KubaPro010@users.noreply.github.com>
Date: Thu, 23 Nov 2023 14:45:55 +0000
Subject: [PATCH] trying to make a option to disable preemphasis

---
 src/pifmrds/fm_mpx.c      | 36 ++++++++++++++++++++----------------
 src/pifmrds/pi_fm_rds.cpp | 26 +++++++++++++-------------
 2 files changed, 33 insertions(+), 29 deletions(-)

diff --git a/src/pifmrds/fm_mpx.c b/src/pifmrds/fm_mpx.c
index 394565b..9ae7278 100644
--- a/src/pifmrds/fm_mpx.c
+++ b/src/pifmrds/fm_mpx.c
@@ -133,21 +133,20 @@ int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int raw
 
         // Create the low-pass FIR filter, with pre-emphasis
         double window, firlowpass, firpreemph , sincpos;
-
+        double taup, deltap, bp, ap, a0, a1, b1;
+        if(preemphasis != 0) {
         // IIR pre-emphasis filter
         // Reference material:    http://jontio.zapto.org/hda1/preempiir.pdf
-        double tau=preemphasis;
-        double delta=1/(2*PI*20000);//double delta=1.96e-6;
-        double taup, deltap, bp, ap, a0, a1, b1;
-        taup=1.0/(2.0*(in_samplerate*FIR_PHASES))/tan(  1.0/(2*tau*(in_samplerate*FIR_PHASES) ));
-        deltap=1.0/(2.0*(in_samplerate*FIR_PHASES))/tan(  1.0/(2*delta*(in_samplerate*FIR_PHASES) ));
-        bp=sqrt( -taup*taup + sqrt(taup*taup*taup*taup + 8.0*taup*taup*deltap*deltap) ) / 2.0 ;
-        ap=sqrt( 2*bp*bp + taup*taup );
-        a0=( 2.0*ap + 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
-        // a1=(-2.0*ap + 1/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1/(in_samplerate*FIR_PHASES) ); //ORI
-        // b1=( 2.0*bp + 1/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1/(in_samplerate*FIR_PHASES) ); //ORI
-        a1=(-2.0*ap + 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
-        b1=( 2.0*bp - 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
+            double tau=preemphasis; //why? well im gonna listen to rule: "if it works dont touch it"
+            double delta=1/(2*PI*20000);//double delta=1.96e-6;
+            taup=1.0/(2.0*(in_samplerate*FIR_PHASES))/tan(  1.0/(2*tau*(in_samplerate*FIR_PHASES) ));
+            deltap=1.0/(2.0*(in_samplerate*FIR_PHASES))/tan(  1.0/(2*delta*(in_samplerate*FIR_PHASES) ));
+            bp=sqrt( -taup*taup + sqrt(taup*taup*taup*taup + 8.0*taup*taup*deltap*deltap) ) / 2.0 ;
+            ap=sqrt( 2*bp*bp + taup*taup );
+            a0=( 2.0*ap + 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
+            a1=(-2.0*ap + 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
+            b1=( 2.0*bp - 1.0/(in_samplerate*FIR_PHASES) )/(2.0*bp + 1.0/(in_samplerate*FIR_PHASES) );
+        }
         double x=0,y=0;
  
         for(int i=0; i<FIR_TAPS; i++) { 
@@ -156,12 +155,17 @@ int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int raw
             sincpos = (mi)-(((FIR_TAPS*FIR_PHASES)+1.0)/2.0); // offset by 0.5 so sincpos!=0 (causes NaN x/0 )
             //printf("%d=%f \n",mi ,sincpos); 
             firlowpass = sin(2 * PI * cutoff_freq * sincpos / (in_samplerate*FIR_PHASES) ) / (PI * sincpos) ; 
-
-            y=a0*firlowpass + a1*x + b1*y ; // Find the combined impulse response
+                                            // Find the combined impulse response
+            if(preemphasis != 0) {
+                y=a0*firlowpass + a1*x + b1*y; 
+            } else {
+                y=firlowpass; 
+            }
             x=firlowpass;                   // of FIR low-pass and IIR pre-emphasis
             firpreemph=y;                   // y could be replaced by firpreemph but this
                                             // matches the example in the reference material
 
+
             window = (.54 - .46 * cos(2*PI * (mi) / (double) FIR_TAPS*FIR_PHASES )) ; // Hamming window
             low_pass_fir[j][i] = firpreemph * window; 
           }
@@ -325,7 +329,7 @@ int fm_mpx_get_samples(float *mpx_buffer, int drds, float compressor_decay, floa
                 if(1) {
                     mpx_buffer[i] +=  4.05*(out_left+out_right) + // Stereo sum signal
                         4.05 * carrier_38[phase_38] * (out_left-out_right) + // Stereo difference signal
-                       pilot_volume*carrier_19[phase_19];                  // Stereo pilot tone (doing 0.1 minus to balance it out, as by default its 0.9, but to make the 1.0 the normal value of the volume)
+                       pilot_volume*carrier_19[phase_19];                  // Stereo pilot tone
 
                     phase_19++;
                     phase_38++;
diff --git a/src/pifmrds/pi_fm_rds.cpp b/src/pifmrds/pi_fm_rds.cpp
index b2d375e..aa28156 100644
--- a/src/pifmrds/pi_fm_rds.cpp
+++ b/src/pifmrds/pi_fm_rds.cpp
@@ -274,7 +274,7 @@ int main(int argc, char **argv) {
     double preemp = 50e-6; //eu
     int deviation = 75000;
     int alternative_freq[100] = {};
-    float ppm = 0;
+    // float ppm = 0; this is useless as the ppm isnt used anywhere anyway
     int bypassfreqrange = 0;
     int ct = 1;
     float cutofffreq = 15700;
@@ -300,9 +300,6 @@ int main(int argc, char **argv) {
         } else if(strcmp("-rt", arg)==0 && param != NULL) {
             i++;
             rt = param;
-        } else if(strcmp("-ppm", arg)==0 && param != NULL) {
-            i++;
-            ppm = atof(param);
         } else if(strcmp("-compressordecay", arg)==0 && param != NULL) {
             i++;
             compressor_decay = atof(param);
@@ -326,12 +323,13 @@ int main(int argc, char **argv) {
             pty = atoi(param);
         } else if(strcmp("-gpiopin", arg)==0 && param != NULL) {
             i++;
-            int pinnum = atoi(param);
-            if (!(pinnum == 4 || pinnum == 20 || pinnum == 32 || pinnum == 34 || pinnum == 6)) {
-                fatal("Invalid gpio pin, allowed: 4, 20, 32, 34, 6");
-            } else {
-                gpiopin = pinnum;
-            }
+            printf("GPIO pin setting disabled, mod librpitx and pifmsa (pifm simply advanced) for this");
+            // int pinnum = atoi(param);
+            // if (!(pinnum == 4 || pinnum == 20 || pinnum == 32 || pinnum == 34 || pinnum == 6)) {
+            //     fatal("Invalid gpio pin, allowed: 4, 20, 32, 34, 6");
+            // } else {
+            //     gpiopin = pinnum;
+            // }
         } else if(strcmp("-ta", arg)==0) {
             i++;
             ta = 1;
@@ -391,7 +389,9 @@ int main(int argc, char **argv) {
             if(strcmp("us", param)==0) {
                 preemp = 75e-6; //usa
             } else if(strcmp("22", param)==0) {
-                preemp = 22e-6; //22
+                preemp = 22e-6; //22, why is it here? ask sdr++ creator
+            } else if(strcmp("off", param)==0) {
+                preemp = 0; //disabled
             }
         } else if(strcmp("-af", arg)==0 && param != NULL) {
             i++;
@@ -402,7 +402,7 @@ int main(int argc, char **argv) {
         }
         else {
             fatal("Unrecognised argument: %s.\n"
-            "Syntax: pi_fm_rds [-freq freq] [-audio file] [-ppm ppm_error] [-pi pi_code]\n"
+            "Syntax: pi_fm_rds [-freq freq] [-audio file] [-pi pi_code]\n"
             "                  [-ps ps_text] [-rt rt_text] [-ctl control_pipe] [-pty program_type] [-raw play raw audio from stdin] [-disablerds] [-af alt freq] [-preemphasis us] [-rawchannels when using the raw option you can change this] [-rawsamplerate same business] [-deviation the deviation, default is 75000, there are 2 predefined other cases: ukf (for old radios such as the UNITRA Jowita), nfm] [-tp] [-ta]\n", arg);
         }
     }
@@ -416,6 +416,6 @@ int main(int argc, char **argv) {
     int FifoSize=DATA_SIZE*2;
     //fmmod=new ngfmdmasync(carrier_freq,228000,14,FifoSize, false, gpiopin); //you can mod
     fmmod=new ngfmdmasync(carrier_freq,228000,14,FifoSize, false);
-    int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe, pty, alternative_freq, raw, drds, preemp, power, rawSampleRate, rawChannels, deviation, ta, tp, cutofffreq, gain, compressor_decay, compressor_attack, compressor_max_gain_recip, enable_compressor, ct, rds_volume, pilot_volume);
+    int errcode = tx(carrier_freq, audio_file, pi, ps, rt, control_pipe, pty, alternative_freq, raw, drds, preemp, power, rawSampleRate, rawChannels, deviation, ta, tp, cutofffreq, gain, compressor_decay, compressor_attack, compressor_max_gain_recip, enable_compressor, ct, rds_volume, pilot_volume);
     terminate(errcode);
 }