diff options
Diffstat (limited to 'util')
| -rw-r--r-- | util/spkmodem_decode/spkmodem-decode.c | 27 |
1 files changed, 16 insertions, 11 deletions
diff --git a/util/spkmodem_decode/spkmodem-decode.c b/util/spkmodem_decode/spkmodem-decode.c index 08e7b17a..ff94e90e 100644 --- a/util/spkmodem_decode/spkmodem-decode.c +++ b/util/spkmodem_decode/spkmodem-decode.c @@ -460,25 +460,30 @@ auto_detect_tone(struct decoder_state *st) { int f; + if (st->learn_samples >= LEARN_SAMPLES) + return; + /* - * Don't also run auto-detect during decode, - * otherwise it would run for every sample. + * Ignore silence / near silence. + * Both FIR windows will be near zero when no signal exists. */ - if (st->learn_samples >= LEARN_SAMPLES) + if (st->freq_data <= 2 && st->freq_separator <= 2) { + st->learn_samples++; return; + } /* - * Check both FIR windows. - * Inside separator frames, the separator window contains tone, - * during data frames the data window does; a minimum of - * the two captures the lowest active tone cluster more reliably. + * Choose the lowest active tone. + * Separator frames carry tone in the separator window, + * data frames carry tone in the data window. */ f = st->freq_data; - if (st->freq_separator > 0 && st->freq_separator < f) + + if (f <= 0 || (st->freq_separator > 0 && + st->freq_separator < f)) f = st->freq_separator; - if (f > 0 || /* prevent noise from corrupting tone-learning */ - st->freq_data > 2 || /* <--- stop from */ - st->freq_separator > 2) { /* learning silence if no signal */ + + if (f > 0) { if (f < st->freq_min) st->freq_min = f; |