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trying to make a option to disable preemphasis

This commit is contained in:
Kuba 2023-11-23 14:45:55 +00:00
parent 66974f2c7e
commit aecd242b97
2 changed files with 33 additions and 29 deletions
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20
src/pifmrds/fm_mpx.c
View File

@ -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 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;
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++) {
@ -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++;

26
src/pifmrds/pi_fm_rds.cpp
View File

@ -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);
}