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minimodem: fsk confidence thresholds: thresh=1.5, limit=2.3 

Note: fsk_confidence_thresh can now be reduced to 1.5 due to track_amplitude.
This commit is contained in:
Kamal Mostafa 2012-08-26 15:16:49 -07:00
parent 3447a994b7
commit becf16761e
2 changed files with 18 additions and 13 deletions
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18
src/minimodem.1.in
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@ -48,19 +48,23 @@ receive mode: decode audio tones
.B \-a, \-\-auto-carrier
automatically detect mark and space frequences from carrier
.TP
.B \-c, \-\-confidence min-snr-threshold
Set receive confidence minimum SNR threshold (default 2.0).
.B \-c, \-\-confidence min-confidence-threshold
Set receive confidence minimum threshold (default 1.5).
The "confidence" value is a metric based primarily on
the SNR (signal-to-noise ratio) of the received signal.
This value acts as an FSK decoder "squelch" control.
Increase to accept only very clean signals (up to INFINITY, but
a value around 5.0 is more practical). Decrease to accept partial
decoding of noisy signals (down to 1.0).
.TP
.B \-l, \-\-limit max-snr-search-limit
Set receive confidence maximum SNR search limit (default 2.3).
decoding of noisy signals (down to a minimum value of 1.0).
(This option applies to \-\-rx mode only).
.B \-l, \-\-limit max-confidence-search-limit
Set receive confidence maximum search limit (default 2.3).
The "confidence" value is as described above.
This value acts as a performance vs. analysis quality control.
Increase (up to INFINITY) for a more pedantic analysis
and higher CPU usage. Decrease (down to the min-snr-threshold)
and higher CPU usage. Decrease (down to the min-confidence-threshold)
for a sloppier analysis, with lower CPU usage.
(This option applies to \-\-rx mode only).
.TP
.B \-8, \-\-ascii
ASCII 8\-N\-1

13
src/minimodem.c
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@ -325,8 +325,8 @@ usage()
" -r, --rx, --receive, --read (default)\n"
" [options]\n"
" -a, --auto-carrier\n"
" -c, --confidence {min-snr-threshold}\n"
" -l, --limit {max-snr-search-limit}\n"
" -c, --confidence {min-confidence-threshold}\n"
" -l, --limit {max-confidence-search-limit}\n"
" -8, --ascii ASCII 8-N-1\n"
" -5, --baudot Baudot 5-N-1\n"
" -f, --file {filename.flac}\n"
@ -370,15 +370,16 @@ main( int argc, char*argv[] )
// fsk_confidence_threshold : signal-to-noise squelch control
//
// The minimum SNR confidence level seen as "a signal".
float fsk_confidence_threshold = 2.0;
// The minimum SNR-ish confidence level seen as "a signal".
float fsk_confidence_threshold = 1.5;
// fsk_confidence_search_limit : performance vs. quality
//
// If we find a frame with SNR confidence > confidence_search_limit,
// If we find a frame with confidence > confidence_search_limit,
// quit searching for a better frame. confidence_search_limit has a
// dramatic effect on peformance (high value yields low performance, but
// higher decode quality, for noisy or hard-to-discern signals (Bell 103).
// higher decode quality, for noisy or hard-to-discern signals (Bell 103,
// or skewed rates).
float fsk_confidence_search_limit = 2.3f;
// float fsk_confidence_search_limit = INFINITY; /* for test */