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minimodem: track_amplitude signal amplitude drop

This commit is contained in:
Kamal Mostafa 2012-08-30 00:07:15 -07:00
parent 1ed3b8465a
commit 3447a994b7
1 changed files with 13 additions and 0 deletions
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13
src/minimodem.c
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@ -783,6 +783,8 @@ main( int argc, char*argv[] )
debug_log("fsk_frame_overscan=%f nsamples_overscan=%u\n",
fsk_frame_overscan, nsamples_overscan);
float track_amplitude = 0.0;
while ( 1 ) {
debug_log("advance=%u\n", advance);
@ -948,6 +950,16 @@ main( int argc, char*argv[] )
&frame_start_sample
);
// no-confidence if amplitude drops abruptly to < 25% of the
// track_amplitude, which follows amplitude with hysteresis
if ( amplitude < track_amplitude * 0.25 ) {
confidence = 0;
} else {
track_amplitude = ( track_amplitude + amplitude ) / 2;
debug_log("@ confidence=%.3f amplitude=%.3f track_amplitude=%.3f\n",
confidence, amplitude, track_amplitude );
}
// chop off framing bits
bits = ( bits >> frame_bits_shift ) & frame_bits_mask;
@ -970,6 +982,7 @@ main( int argc, char*argv[] )
amplitude_total = 0;
nframes_decoded = 0;
nbits_decoded = 0;
track_amplitude = 0.0;
}
if ( rx_one )