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rtl_fm: dc block from TonberryKing 

Signed-off-by: Steve Markgraf <steve@steve-m.de>
This commit is contained in:
Kyle Keen 2013-01-30 00:33:11 -05:00 committed by Steve Markgraf
parent e8e735caf4
commit 8d358b44d4
1 changed files with 30 additions and 15 deletions
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45
src/rtl_fm.c
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@ -78,18 +78,13 @@ static int atan_lut_coef = 8;
struct fm_state
{
int now_r;
int now_j;
int pre_r;
int pre_j;
int now_r, now_j;
int pre_r, pre_j;
int prev_index;
int downsample; /* min 1, max 256 */
int post_downsample;
int output_scale;
int squelch_level;
int conseq_squelch;
int squelch_hits;
int terminate_on_squelch;
int squelch_level, conseq_squelch, squelch_hits, terminate_on_squelch;
int exit_flag;
uint8_t buf[MAXIMUM_BUF_LENGTH];
uint32_t buf_len;
@ -108,10 +103,10 @@ struct fm_state
int fir[256]; /* fir_len == downsample */
int fir_sum;
int custom_atan;
int deemph;
int deemph_a;
int deemph, deemph_a;
int now_lpr;
int prev_lpr_index;
int dc_block, dc_avg;
void (*mode_demod)(struct fm_state*);
};
@ -146,6 +141,7 @@ void usage(void)
"\t[-R enables raw mode (default: off, 2x16 bit output)]\n"
"\t[-F enables high quality FIR (default: off/square)]\n"
"\t[-D enables de-emphasis (default: off)]\n"
"\t[-C enables DC blocking of output (default: off)]\n"
"\t[-A std/fast/lut choose atan math (default: std)]\n\n"
"Produces signed 16 bit ints, use Sox or aplay to hear them.\n"
"\trtl_fm ... - | play -t raw -r 24k -e signed-integer -b 16 -c 1 -V1 -\n"
@ -488,6 +484,21 @@ void deemph_filter(struct fm_state *fm)
}
}
void dc_block_filter(struct fm_state *fm)
{
int i, avg;
int64_t sum = 0;
for (i=0; i < fm->signal2_len; i++) {
sum += fm->signal2[i];
}
avg = sum / fm->signal2_len;
avg = (avg + fm->dc_avg * 9) / 10;
for (i=0; i < fm->signal2_len; i++) {
fm->signal2[i] -= avg;
}
fm->dc_avg = avg;
}
int mad(int *samples, int len, int step)
/* mean average deviation */
{
@ -591,6 +602,8 @@ void full_demod(struct fm_state *fm)
}
if (fm->deemph) {
deemph_filter(fm);}
if (fm->dc_block) {
dc_block_filter(fm);}
/* ignore under runs for now */
fwrite(fm->signal2, 2, fm->signal2_len, fm->file);
if (hop) {
@ -689,13 +702,12 @@ void fm_init(struct fm_state *fm)
fm->deemph = 0;
fm->output_rate = -1; // flag for disabled
fm->mode_demod = &fm_demod;
fm->pre_j = 0;
fm->pre_r = 0;
fm->now_r = 0;
fm->now_j = 0;
fm->pre_j = fm->pre_r = fm->now_r = fm->now_j = 0;
fm->prev_lpr_index = 0;
fm->deemph_a = 0;
fm->now_lpr = 0;
fm->dc_block = 0;
fm->dc_avg = 0;
}
int main(int argc, char **argv)
@ -715,7 +727,7 @@ int main(int argc, char **argv)
fm_init(&fm);
sem_init(&data_ready, 0, 0);
while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRD")) != -1) {
while ((opt = getopt(argc, argv, "d:f:g:s:b:l:o:t:r:p:EFA:NWMULRDC")) != -1) {
switch (opt) {
case 'd':
dev_index = atoi(optarg);
@ -774,6 +786,9 @@ int main(int argc, char **argv)
case 'D':
fm.deemph = 1;
break;
case 'C':
fm.dc_block = 1;
break;
case 'N':
fm.mode_demod = &fm_demod;
break;