def report_carrier(bufs, begin):
x = np.concatenate(tuple(bufs)[-CARRIER_THRESHOLD:-1])
Hc = sigproc.exp_iwt(-config.Fc, len(x))
Zc = np.dot(Hc, x) / (0.5*len(x))
amp = abs(Zc)
log.info('Carrier detected at ~%.1f ms @ %.1f kHz:'
' coherence=%.3f%%, amplitude=%.3f',
begin * config.Tsym * 1e3 / config.Nsym, config.Fc / 1e3,
np.abs(sigproc.coherence(x, config.Fc)) * 100, amp)
return amp
def detect(samples, freq):
counter = 0
bufs = collections.deque([], maxlen=config.baud) # 1 second of symbols
for offset, buf in common.iterate(samples, config.Nsym):
bufs.append(buf)
coeff = sigproc.coherence(buf, config.Fc)
if abs(coeff) > COHERENCE_THRESHOLD:
counter += 1
else:
counter = 0
if counter == CARRIER_THRESHOLD:
length = (CARRIER_THRESHOLD - 1) * config.Nsym
begin = offset - length
amplitude = report_carrier(bufs, begin=begin)
break
else:
raise ValueError('No carrier detected')
log.debug('Buffered %d ms of audio', len(bufs))
to_append = SEARCH_WINDOW + (CARRIER_DURATION - CARRIER_THRESHOLD)
bufs_iterator = common.iterate(samples, config.Nsym)
for _, buf in itertools.islice(bufs_iterator, to_append):
bufs.append(buf)
bufs = tuple(bufs)[-CARRIER_DURATION-2*SEARCH_WINDOW:]
buf = np.concatenate(bufs)
offset = find_start(buf, length=config.Nsym*CARRIER_DURATION)
start = begin - config.Nsym * SEARCH_WINDOW + offset
log.info('Carrier starts at %.3f ms',
start * config.Tsym * 1e3 / config.Nsym)
return itertools.chain(buf[offset:], samples), amplitude
