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minimodem: rate analysis fixes ("rate perfect") 

adjust MIN_CONFIDENCE
This commit is contained in:
Kamal Mostafa 2011-07-08 13:03:00 -07:00
parent bca34371e1
commit 7a5aea88df
1 changed files with 33 additions and 11 deletions
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44
src/minimodem.c
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@ -138,21 +138,33 @@ static void
report_no_carrier( fsk_plan *fskp,
unsigned int sample_rate,
float bfsk_data_rate,
float nsamples_per_bit,
unsigned int nframes_decoded,
size_t carrier_nsamples,
float confidence_total )
{
unsigned long long nbits_total = nframes_decoded * (fskp->n_data_bits+2);
#if 0
fprintf(stderr, "nframes_decoded=%u\n", nframes_decoded);
fprintf(stderr, "nbits_total=%llu\n", nbits_total);
fprintf(stderr, "carrier_nsamples=%lu\n", carrier_nsamples);
fprintf(stderr, "nsamples_per_bit=%f\n", nsamples_per_bit);
#endif
float throughput_rate = nbits_total * sample_rate / (float)carrier_nsamples;
float throughput_skew = (throughput_rate - bfsk_data_rate)
/ bfsk_data_rate;
fprintf(stderr, "### NOCARRIER ndata=%u confidence=%.2f throughput=%.2f (%.1f%% %s) ###\n",
fprintf(stderr, "### NOCARRIER ndata=%u confidence=%.2f throughput=%.2f",
nframes_decoded,
confidence_total / nframes_decoded,
throughput_rate,
fabs(throughput_skew) * 100.0,
signbit(throughput_skew) ? "slow" : "fast"
);
throughput_rate);
if ( (size_t)(nbits_total * nsamples_per_bit + 0.5) == carrier_nsamples ) {
fprintf(stderr, " (rate perfect) ###\n");
} else {
float throughput_skew = (throughput_rate - bfsk_data_rate)
/ bfsk_data_rate;
fprintf(stderr, " (%.1f%% %s) ###\n",
fabs(throughput_skew) * 100.0,
signbit(throughput_skew) ? "slow" : "fast"
);
}
}
void
@ -577,7 +589,9 @@ main( int argc, char*argv[] )
break;
unsigned int try_max_nsamples = nsamples_per_bit;
#define FSK_ANALYZE_NSTEPS 8 /* accuracy vs. performance */
#define FSK_ANALYZE_NSTEPS 10 /* accuracy vs. performance */
// Note: FSK_ANALYZE_NSTEPS has subtle effects on the
// "rate perfect" calculation. oh well.
unsigned int try_step_nsamples = nsamples_per_bit / FSK_ANALYZE_NSTEPS;
if ( try_step_nsamples == 0 )
try_step_nsamples = 1;
@ -601,9 +615,11 @@ main( int argc, char*argv[] )
else
bits = ( bits >> 2 ) & 0xFF;
#define FSK_MIN_CONFIDENCE 0.50
#define FSK_MIN_CONFIDENCE 0.60
#define FSK_MAX_NOCONFIDENCE_BITS 20
#define FSK_SCAN_LAG 0.2
if ( confidence <= FSK_MIN_CONFIDENCE ) {
// FIXME: explain
if ( ++noconfidence > FSK_MAX_NOCONFIDENCE_BITS )
@ -613,7 +629,10 @@ main( int argc, char*argv[] )
#endif
if ( carrier ) {
carrier_nsamples -= noconfidence_nsamples;
if ( nframes_decoded > 0 )
carrier_nsamples += nsamples_per_bit * FSK_SCAN_LAG;
report_no_carrier(fskp, sample_rate, bfsk_data_rate,
nsamples_per_bit,
nframes_decoded, carrier_nsamples, confidence_total);
carrier = 0;
carrier_nsamples = 0;
@ -640,6 +659,8 @@ main( int argc, char*argv[] )
bfsk_data_rate,
fskp->b_mark * fskp->band_width);
carrier = 1;
/* back up carrier_nsamples to account for the imminent advance */
noconfidence_nsamples = frame_start_sample;
bfsk_framebits_decode(0, 0, 0); /* reset the frame processor */
}
@ -647,7 +668,6 @@ main( int argc, char*argv[] )
confidence_total += confidence;
nframes_decoded++;
noconfidence = 0;
noconfidence_nsamples = 0;
/* Advance the sample stream forward past the decoded frame
* but not past the stop bit, since we want it to appear as
@ -658,7 +678,6 @@ main( int argc, char*argv[] )
* but actually advance just a bit less than that to allow
* for clock skew, hence FSK_SCAN_LAG.
*/
#define FSK_SCAN_LAG 0.2
advance = frame_start_sample +
nsamples_per_bit * (float)(fskp->n_data_bits + 2 - FSK_SCAN_LAG);
@ -697,7 +716,10 @@ main( int argc, char*argv[] )
if ( carrier ) {
carrier_nsamples -= noconfidence_nsamples;
if ( nframes_decoded > 0 )
carrier_nsamples += nsamples_per_bit * FSK_SCAN_LAG;
report_no_carrier(fskp, sample_rate, bfsk_data_rate,
nsamples_per_bit,
nframes_decoded, carrier_nsamples, confidence_total);
}