radio95/fm95
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implement bs412 mpx deviation and implement a peak limiter

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KubaPro010
2025-04-04 14:23:08 +02:00
parent b23db0d109
commit a82ea1af6e
2 changed files with 21 additions and 8 deletions
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2
.vscode/.server-controller-port.log vendored
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@@ -1,5 +1,5 @@
{
"port": 13452,
"time": 1743357198315,
"time": 1743768242698,
"version": "0.0.3"
}

27
src/fm95.c
View File

@@ -14,6 +14,7 @@
#define DEFAULT_SCA_CLIPPER_THRESHOLD 1.0f
#define DEFAULT_PREEMPHASIS_TAU 50e-6 // Europe, the freedomers use 75µs
#define DEFAULT_MPX_POWER 3.0f // dbr, this is for BS412, simplest bs412
#define DEFAULT_MPX_DEVIATION 75000 // for BS412
#include "../lib/constants.h"
#include "../lib/oscillator.h"
@@ -95,6 +96,7 @@ void show_help(char *name) {
" -R,--preemp Override preemphasis [default: %.2f µs]\n"
" -V,--calibrate Enable Calibration mode [default: off]\n"
" -p,--power Set the MPX power [default: %.1f]\n"
" -d,--mpx_dev Set the MPX deviation [default: %.1f]\n"
" -A,--master_vol Set master volume [default: %.3f]\n"
" -v,--audio_vol Set audio volume [default: %.3f]\n"
,name
@@ -123,6 +125,7 @@ void show_help(char *name) {
,(DEFAULT_STEREO_POLAR == 1) ? ", default" : ""
,DEFAULT_PREEMPHASIS_TAU/0.000001
,DEFAULT_MPX_POWER
,DEFAULT_MPX_DEVIATION
,DEFAULT_MASTER_VOLUME
,DEFAULT_AUDIO_VOLUME
);
@@ -167,6 +170,7 @@ int main(int argc, char **argv) {
int calibration_mode = 0;
float mpx_power = DEFAULT_MPX_POWER;
float mpx_deviation = DEFAULT_MPX_DEVIATION;
float master_volume = DEFAULT_MASTER_VOLUME;
float audio_volume = DEFAULT_AUDIO_VOLUME;
@@ -174,7 +178,7 @@ int main(int argc, char **argv) {
// #region Parse Arguments
int opt;
const char *short_opt = "s::i:o:M:r:C:f:F:L:c:P::R:Vp:A:v:h";
const char *short_opt = "s::i:o:M:r:C:f:F:L:c:P::R:Vp:d:A:v:h";
struct option long_opt[] =
{
{"stereo", optional_argument, NULL, 's'},
@@ -191,6 +195,7 @@ int main(int argc, char **argv) {
{"preemp", required_argument, NULL, 'R'},
{"calibrate", no_argument, NULL, 'V'},
{"power", required_argument, NULL, 'p'},
{"mpx_dev", required_argument, NULL, 'd'},
{"master_vol", required_argument, NULL, 'A'},
{"audio_vol", required_argument, NULL, 'v'},
@@ -250,6 +255,13 @@ int main(int argc, char **argv) {
case 'p': // Power
mpx_power = strtof(optarg, NULL);
break;
case 'd': // MPX deviation
mpx_deviation = strtof(optarg, NULL);
if (mpx_deviation < 38000) {
fprintf(stderr, "Warning: MPX deviation cannot be lower than 38000. Setting to 38000.\n");
mpx_deviation = 38000;
}
break;
case 'A': // Master vol
master_volume = strtof(optarg, NULL);
break;
@@ -528,14 +540,15 @@ int main(int argc, char **argv) {
if(mpx_on) mpx += hard_clip(current_mpx_in, MPX_CLIPPER_THRESHOLD)*MPX_VOLUME;
if(sca_on) mpx += modulate_fm(&sca_mod, hard_clip(current_sca_in, sca_clipper_threshold))*SCA_VOLUME;
float mpower = measure_mpx(&power, (audio+mpx) * 75000);
float mpower = measure_mpx(&power, (audio+mpx) * mpx_deviation);
if (mpower > mpx_power) {
float excess_power = mpower - mpx_power;
float reduction_factor_db = excess_power;
float reduction_factor_linear = powf(10.0f, -reduction_factor_db / 20.0f);
audio *= reduction_factor_linear;
audio *= powf(10.0f, -excess_power / 20.0f);
}
float mpower_peak = deviation_to_dbr((audio+mpx) * mpx_deviation);
if (mpower_peak > (mpx_power+0.1f)) { // According to the FM22 standard (https://cept.org/documents/fm-22/16691/fm22-14-14_fm-broadcast-deviation-and-mpx-measurements) the peak power should never be more than 0.1 dB above the designated power
float excess_power = mpower_peak - (mpx_power+0.1f);
audio *= powf(10.0f, -excess_power / 20.0f);
}
output[i] = (audio+mpx)*master_volume;