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fsk: new confidence algo

This commit is contained in:
Kamal Mostafa 2011-06-22 10:06:19 -07:00
parent 2b014b50fb
commit 3a22116159
2 changed files with 22 additions and 5 deletions
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20
src/fsk.c
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@ -214,7 +214,7 @@ fsk_frame_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
fsk_bits_analyze(fskp, samples+begin_databits, samples_per_bit,
bits_outp, databit_strengths);
// computer average bit strength 'v'
// compute average bit strength 'v'
int i;
for ( i=0; i<fskp->n_data_bits; i++ )
v += databit_strengths[i];
@ -224,6 +224,10 @@ fsk_frame_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
if ( v < FSK_MIN_STRENGTH )
return 0.0;
#define CONFIDENCE_ALGO 2
#if ( CONFIDENCE_ALGO == 1 )
float confidence = 0;
confidence += 1.0 - fabs(i_str - v);
confidence += 1.0 - fabs(s_str - v);
@ -232,6 +236,20 @@ fsk_frame_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
confidence += 1.0 - fabs(databit_strengths[i] - v);
confidence /= (fskp->n_data_bits + 3);
#elif ( CONFIDENCE_ALGO == 2 )
float confidence = 0;
confidence += i_str;
confidence += s_str;
confidence += p_str;
for ( i=0; i<fskp->n_data_bits; i++ )
confidence += databit_strengths[i];
confidence /= (fskp->n_data_bits + 3);
#endif
debug_log(" frame confidence (algo #%u) = %f\n",
CONFIDENCE_ALGO, confidence);
return confidence;
}

7
src/minimodem.c
View File

@ -525,7 +525,6 @@ main( int argc, char*argv[] )
if ( samples_nvalid < frame_nsamples )
break;
// FIXME: explain
unsigned int try_max_nsamples = nsamples_per_bit;
#define FSK_ANALYZE_NSTEPS 8 /* accuracy vs. performance */
unsigned int try_step_nsamples = nsamples_per_bit / FSK_ANALYZE_NSTEPS;
@ -545,7 +544,7 @@ main( int argc, char*argv[] )
&frame_start_sample
);
#define FSK_MIN_CONFIDENCE 0.5 /* not critical */
#define FSK_MIN_CONFIDENCE 0.05
#define FSK_MAX_NOCONFIDENCE_BITS 20
if ( confidence <= FSK_MIN_CONFIDENCE ) {
@ -600,9 +599,9 @@ main( int argc, char*argv[] )
* advance = 1 prev_stop + 1 start + N data bits == n_data_bits+2
*
* but actually advance just a bit less than that to allow
* for clock skew, so ...
* for clock skew, hence FSK_SCAN_LAG.
*/
#define FSK_SCAN_LAG 0.4
#define FSK_SCAN_LAG 0.2
advance = frame_start_sample +
nsamples_per_bit * (float)(fskp->n_data_bits + 2 - FSK_SCAN_LAG);