diff --git a/src/pifmrds/fm_mpx.c b/src/pifmrds/fm_mpx.c
index 85a39d8..f6d7fc1 100644
--- a/src/pifmrds/fm_mpx.c
+++ b/src/pifmrds/fm_mpx.c
@@ -65,6 +65,7 @@ float fir_buffer_left[FIR_TAPS] = {0};
 float fir_buffer_right[FIR_TAPS] = {0};
 int fir_index = 0;
 int channels;
+int in_samplerate;
 float left_max=1, right_max=1;  // start compressor with low gain 
 
 SNDFILE *inf;
@@ -81,7 +82,7 @@ float *alloc_empty_buffer(size_t length) {
 }
 
 
-int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int rawSampleRate, int rawChannels, float cutoff_freq) {
+int fm_mpx_open(char *filename, size_t len, int raw, int rawSampleRate, int rawChannels) {
     length = len;
     raw_ = raw;
 
@@ -112,7 +113,7 @@ int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int raw
             }
         }
             
-        int in_samplerate = sfinfo.samplerate;
+        in_samplerate = sfinfo.samplerate;
         downsample_factor = 228000. / in_samplerate;
     
         printf("Input: %d Hz, upsampling factor: %.2f\n", in_samplerate, downsample_factor);
@@ -124,48 +125,6 @@ int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int raw
             printf("1 channel, monophonic operation.\n");
         }
     
-        // Choose a cutoff frequency for the low-pass FIR filter
-        if(in_samplerate/2 < cutoff_freq) cutoff_freq = in_samplerate/2 * .8;
-   
-
-        // Create the low-pass FIR filter, with pre-emphasis
-        double window, firlowpass, firpreemph , sincpos;
-
-        // 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 x=0,y=0;
- 
-        for(int i=0; i<FIR_TAPS; i++) { 
-         for(int j=0; j<FIR_PHASES; j++) {
-            int mi=i*FIR_PHASES + j+1;// match indexing of Matlab script
-            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
-            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; 
-          }
-        }
-    
-        printf("Created low-pass FIR filter for audio channels, with cutoff at %.1f Hz\n", cutoff_freq);
-    
         if( 0 )
         {
           printf("f = [ ");
@@ -193,7 +152,43 @@ int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int raw
 
 // samples provided by this function are in 0..10: they need to be divided by
 // 10 after.
-int fm_mpx_get_samples(float *mpx_buffer, int drds, float compressor_decay, float compressor_attack, float compressor_max_gain_recip, int disablestereo, float gain, int enablecompressor, int rds_ct_enabled, float rds_volume, int paused) {
+int fm_mpx_get_samples(float *mpx_buffer, int drds, float compressor_decay, float compressor_attack, float compressor_max_gain_recip, int disablestereo, float gain, int enablecompressor, int rds_ct_enabled, float rds_volume, int paused, double preemphasis, float cutoff_freq) {
+    // Choose a cutoff frequency for the low-pass FIR filter
+    if(in_samplerate/2 < cutoff_freq) cutoff_freq = in_samplerate/2 * .8;
+    // Create the low-pass FIR filter, with pre-emphasis
+    double window, firlowpass, firpreemph , sincpos;
+    // 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 x=0,y=0;
+    for(int i=0; i<FIR_TAPS; i++) { 
+         for(int j=0; j<FIR_PHASES; j++) {
+            int mi=i*FIR_PHASES + j+1;// match indexing of Matlab script
+            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
+            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; 
+          }
+        }
+    
     int stereo_capable = (channels > 1) && (!disablestereo); //chatgpt
     if(!drds) get_rds_samples(mpx_buffer, length, stereo_capable, rds_ct_enabled, rds_volume);
 
diff --git a/src/pifmrds/fm_mpx.h b/src/pifmrds/fm_mpx.h
index 8407eb8..c337ebf 100644
--- a/src/pifmrds/fm_mpx.h
+++ b/src/pifmrds/fm_mpx.h
@@ -21,6 +21,6 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-extern int fm_mpx_open(char *filename, size_t len, int raw, double preemphasis, int rawSampleRate, int rawChannels, float cutoff_freq);
-extern int fm_mpx_get_samples(float *mpx_buffer, int drds, float compressor_decay, float compressor_attack, float compressor_max_gain_recip, int disablestereo, float gain, int enablecompressor, int rds_ct_enabled, float rds_volume, int paused);
+extern int fm_mpx_open(char *filename, size_t len, int raw, int rawSampleRate, int rawChannels);
+extern int fm_mpx_get_samples(float *mpx_buffer, int drds, float compressor_decay, float compressor_attack, float compressor_max_gain_recip, int disablestereo, float gain, int enablecompressor, int rds_ct_enabled, float rds_volume, int paused, double preemphasis, float cutoff_freq);
 extern int fm_mpx_close();
diff --git a/src/pifmrds/pi_fm_rds.cpp b/src/pifmrds/pi_fm_rds.cpp
index 645d846..6e5f1f8 100644
--- a/src/pifmrds/pi_fm_rds.cpp
+++ b/src/pifmrds/pi_fm_rds.cpp
@@ -117,7 +117,7 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
     int disablestereo = 0;
 
     // Initialize the baseband generator
-    if(fm_mpx_open(audio_file, DATA_SIZE, raw, preemp, rawSampleRate, rawChannels, cutoff_freq) < 0) return 1;
+    if(fm_mpx_open(audio_file, DATA_SIZE, raw, rawSampleRate, rawChannels) < 0) return 1;
 
     // Initialize the RDS modulator
     char myps[9] = {0};
@@ -223,7 +223,7 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
             }
         }
 
-			if( fm_mpx_get_samples(data, drds, compressor_decay, compressor_attack, compressor_max_gain_recip, disablestereo, gaim, enablecompressor, rds_ct_enabled, rds_volume, 0) < 0 ) {
+			if( fm_mpx_get_samples(data, drds, compressor_decay, compressor_attack, compressor_max_gain_recip, disablestereo, gaim, enablecompressor, rds_ct_enabled, rds_volume, 0, cutoff_freq, preemp) < 0 ) {
                     terminate(0);
                 }
                 data_len = DATA_SIZE;