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PiFmRds
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The lowpass cutoff frequency is now configurable via CLI 

with -cutoff [compliant/quality/{cutoff freq}] you can now select the cutoff frequency
This commit is contained in:
Florian Schöck 2016-03-12 19:34:02 +01:00
parent d81db0e798
commit 43d9431d30
3 changed files with 19 additions and 7 deletions
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4
src/fm_mpx.c
View File

@ -84,7 +84,7 @@ float *alloc_empty_buffer(size_t length) {
}
int fm_mpx_open(char *filename, size_t len, float preemphasis_corner_freq) {
int fm_mpx_open(char *filename, size_t len, float cutoff_freq, float preemphasis_corner_freq) {
length = len;
if(filename != NULL) {
@ -130,11 +130,9 @@ int fm_mpx_open(char *filename, size_t len, float preemphasis_corner_freq) {
// Create the low-pass FIR filter
float cutoff_freq = 22050;
if(in_samplerate/2 < cutoff_freq) cutoff_freq = in_samplerate/2;
low_pass_fir[FIR_HALF_SIZE-1] = 2 * cutoff_freq / 228000 /2;
// Here we divide this coefficient by two because it will be counted twice
// when applying the filter

2
src/fm_mpx.h
View File

@ -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, float preemphasis_corner_freq);
extern int fm_mpx_open(char *filename, size_t len, float cutoff_freq, float preemphasis_corner_freq);
extern int fm_mpx_get_samples(float *mpx_buffer);
extern int fm_mpx_close();

20
src/pi_fm_rds.c
View File

@ -310,7 +310,7 @@ map_peripheral(uint32_t base, uint32_t len)
#define DATA_SIZE 5000
int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt, float ppm, char *control_pipe, float preemphasis_cutoff) {
int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt, float ppm, char *control_pipe, float cutoff, float preemphasis_cutoff) {
// Catch all signals possible - it is vital we kill the DMA engine
// on process exit!
for (int i = 0; i < 64; i++) {
@ -445,7 +445,7 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
int data_index = 0;
// Initialize the baseband generator
if(fm_mpx_open(audio_file, DATA_SIZE, preemphasis_cutoff) < 0) return 1;
if(fm_mpx_open(audio_file, DATA_SIZE, cutoff, preemphasis_cutoff) < 0) return 1;
// Initialize the RDS modulator
char myps[9] = {0};
@ -539,6 +539,9 @@ int tx(uint32_t carrier_freq, char *audio_file, uint16_t pi, char *ps, char *rt,
#define PREEMPHASIS_EU 3185
#define PREEMPHASIS_US 2120
#define CUTOFF_COMPLIANT 15000
#define CUTOFF_QUALITY 22050
int main(int argc, char **argv) {
char *audio_file = NULL;
char *control_pipe = NULL;
@ -547,6 +550,7 @@ int main(int argc, char **argv) {
char *rt = "PiFmRds: live FM-RDS transmission from the RaspberryPi";
uint16_t pi = 0x1234;
float ppm = 0;
float cutoff = CUTOFF_COMPLIANT;
float preemphasis_cutoff = PREEMPHASIS_US;
@ -590,6 +594,16 @@ int main(int argc, char **argv) {
else {
preemphasis_cutoff = atof(param);
}
} else if(strcmp("-cutoff", arg)==0 && param != NULL) {
i++;
if(strcmp("compliant", param)==0) {
cutoff = CUTOFF_COMPLIANT;
} else if(strcmp("quality", param)==0) {
cutoff = CUTOFF_QUALITY;
}
else {
cutoff = atof(param);
}
} else {
fatal("Unrecognised argument: %s.\n"
"Syntax: pi_fm_rds [-freq freq] [-audio file] [-ppm ppm_error] [-pi pi_code]\n"
@ -597,7 +611,7 @@ int main(int argc, char **argv) {
}
}
int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe, preemphasis_cutoff);
int errcode = tx(carrier_freq, audio_file, pi, ps, rt, ppm, control_pipe, cutoff, preemphasis_cutoff);
terminate(errcode);
}