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fsk: fix noise <= EPSILON handling 

Handle noise <= EPSILON better; fixes (im)perfect test cases on i386.
This commit is contained in:
Kamal Mostafa 2012-08-19 15:58:08 -07:00
parent 96ec6450bb
commit e9263c9c9d
1 changed files with 10 additions and 10 deletions
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20
src/fsk.c
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@ -21,6 +21,7 @@
#include <malloc.h> #include <malloc.h>
#include <string.h> #include <string.h>
#include <math.h> // fabs, hypotf #include <math.h> // fabs, hypotf
#include <float.h> // FLT_EPSILON
#include <errno.h> #include <errno.h>
#include <stdio.h> #include <stdio.h>
#include <ctype.h> #include <ctype.h>
@ -274,25 +275,24 @@ fsk_frame_analyze( fsk_plan *fskp, float *samples, float samples_per_bit,
float total_bit_sig = 0.0, total_bit_noise = 0.0; float total_bit_sig = 0.0, total_bit_noise = 0.0;
for ( bitnum=0; bitnum<(n_bits-1); bitnum++ ) { for ( bitnum=0; bitnum<(n_bits-1); bitnum++ ) {
// Deal with floating point data type quantization noise...
// If total_bit_noise <= FLT_EPSILON, then assume it to be 0.0,
// so that we end up with snr==inf.
total_bit_sig += bit_sig_mags[bitnum]; total_bit_sig += bit_sig_mags[bitnum];
total_bit_noise += bit_noise_mags[bitnum]; if ( bit_noise_mags[bitnum] > FLT_EPSILON )
total_bit_noise += bit_noise_mags[bitnum];
} }
// Deal with floating point data type quantization noise...
// If total_bit_noise is so small that (sig-noise) appears to == sig,
// then force noise=0.0, so that we end up with snr==inf.
float d = total_bit_sig - total_bit_noise;
if ( d == total_bit_sig)
total_bit_noise = 0.0f;
// Compute the "frame SNR" // Compute the "frame SNR"
float snr = total_bit_sig / total_bit_noise; float snr = total_bit_sig / total_bit_noise;
float avg_bit_sig = total_bit_sig / (n_bits-1); float avg_bit_sig = total_bit_sig / (n_bits-1);
#ifdef FSK_DEBUG #ifdef FSK_DEBUG
float avg_bit_noise = total_bit_noise / (n_bits-1); float avg_bit_noise = total_bit_noise / (n_bits-1);
debug_log(" snr=%.6f avg{ bit_sig=%.6f bit_noise=%.6f }\n", debug_log(" snr=%.6f avg{ bit_sig=%.6f bit_noise=%.6f (%s) }\n",
snr, avg_bit_sig, avg_bit_noise); snr, avg_bit_sig, avg_bit_noise,
avg_bit_noise == 0.0 ? "zero" : "non-zero"
);
#endif #endif
# ifdef FSK_MIN_MAGNITUDE # ifdef FSK_MIN_MAGNITUDE