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fsk_bits_analyze / fsk_frame_analyze rework 

- confidence calc only uses data bits metrics (for good or ill)
This commit is contained in:
Kamal Mostafa 2011-06-12 12:42:08 -07:00
parent 1bfd5ada5b
commit 775ef649e1
1 changed files with 57 additions and 39 deletions
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96
src/fsk.c
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@ -127,14 +127,58 @@ fsk_bit_analyze( fsk_plan *fskp, float *samples, unsigned int bit_nsamples,
}
/* returns confidence value [0.0 to 1.0] */
static float
fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
fsk_bits_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
unsigned int *bits_outp )
{
unsigned int bit_nsamples = (float)(samples_per_bit + 0.5);
unsigned int nbits = fskp->n_data_bits;
float v = 0;
unsigned int bits_out = 0;
int i;
float d_str[32];
for ( i=0; i<nbits; i++ ) {
unsigned int begin_databit = (float)(samples_per_bit * i + 0.5);
unsigned int bit;
debug_log("\t\tdata begin_data_bit=%u ", begin_databit);
fsk_bit_analyze(fskp, samples+begin_databit, bit_nsamples,
&bit, &d_str[i]);
v += d_str[i];
bits_out |= bit << i;
}
*bits_outp = bits_out;
/* Compute frame decode confidence as the inverse of the average
* bit-strength delta from the average bit-strength. (whew).*/
v /= nbits; /* v = average bit-strength */
/*
* Filter out noise below FSK_MIN_STRENGTH threshold
*/
#define FSK_MIN_STRENGTH 0.05
if ( v < FSK_MIN_STRENGTH )
return 0.0;
float confidence = 0;
for ( i=0; i<nbits; i++ ) {
confidence += 1.0 - fabs(d_str[i] - v);
}
confidence /= nbits;
debug_log(__func__ " confidence=%f\n", confidence );
return confidence;
}
/* returns confidence value [0.0 to 1.0] */
static float
fsk_frame_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
unsigned int *bits_outp )
{
float v = 0;
float samples_per_bit = (float)frame_nsamples / fskp->n_frame_bits;
unsigned int bit_nsamples = (float)(samples_per_bit + 0.5);
// 0123456789A
@ -146,6 +190,7 @@ fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
unsigned int begin_idlebit = 0;
unsigned int begin_startbit = (float)(samples_per_bit * 1 + 0.5);
unsigned int begin_databits = (float)(samples_per_bit * 2 + 0.5);
unsigned int begin_stopbit = (float)(samples_per_bit * (fskp->n_data_bits+2) + 0.5);
/*
@ -188,45 +233,16 @@ fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
return 0.0;
v += i_str;
unsigned int bits_out = 0;
int i;
float d_str[32];
for ( i=0; i<fskp->n_data_bits; i++ ) {
debug_log("\t\tdata ");
unsigned int begin_databit = (float)(samples_per_bit * (i+2) + 0.5);
fsk_bit_analyze(fskp, samples+begin_databit, bit_nsamples,
&bit, &d_str[i]);
v += d_str[i];
bits_out |= bit << i;
}
*bits_outp = bits_out;
// FIXME -- we're not actually even using 'v' from above
// Analyze the actual data payload bits
float confidence;
confidence = fsk_bits_analyze(fskp, samples+begin_databits,
samples_per_bit, bits_outp);
/* Compute frame decode confidence as the inverse of the average
* bit-strength delta from the average bit-strength. (whew).*/
v /= fskp->n_frame_bits; /* v = average bit-strength */
/*
* Filter out noise below FSK_MIN_STRENGTH threshold
*/
#define FSK_MIN_STRENGTH 0.05
if ( v < FSK_MIN_STRENGTH )
return 0.0;
float confidence = 0;
confidence += 1.0 - fabs(i_str - v);
confidence += 1.0 - fabs(s_str - v);
confidence += 1.0 - fabs(p_str - v);
for ( i=0; i<fskp->n_data_bits; i++ ) {
confidence += 1.0 - fabs(d_str[i] - v);
}
confidence /= fskp->n_frame_bits;
debug_log( "frame decode confidence=%f\n", confidence );
return confidence;
}
/* returns confidence value [0.0 to 1.0] */
float
fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
@ -236,6 +252,8 @@ fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
unsigned int *frame_start_outp
)
{
float samples_per_bit = (float)frame_nsamples / fskp->n_frame_bits;
unsigned int t;
unsigned int best_t = 0;
float best_c = 0.0;
@ -244,8 +262,8 @@ fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
{
float c;
unsigned int bits_out = 0;
debug_log("try fsk_frame_decode(skip=%+d)\n", t);
c = fsk_frame_decode(fskp, samples+t, frame_nsamples, &bits_out);
debug_log("try fsk_frame_analyze(skip=%+d)\n", t);
c = fsk_frame_analyze(fskp, samples+t, samples_per_bit, &bits_out);
if ( best_c < c ) {
best_t = t;
best_c = c;