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detect: refactor find_start()

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Roman Zeyde
2015-02-17 18:08:57 +02:00
parent e06cb37e2b
commit 61dc35c122
1 changed files with 4 additions and 4 deletions
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8
amodem/detect.py
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@@ -17,6 +17,7 @@ class Detector(object):
CARRIER_DURATION = sum(equalizer.prefix)
CARRIER_THRESHOLD = int(0.9 * CARRIER_DURATION)
SEARCH_WINDOW = int(0.1 * CARRIER_DURATION)
START_PATTERN_LENGTH = SEARCH_WINDOW // 4
TIMEOUT = 10.0 # [seconds]
@@ -78,7 +79,7 @@ class Detector(object):
def find_start(self, buf):
carrier = dsp.exp_iwt(self.omega, self.Nsym)
carrier = np.tile(carrier, self.SEARCH_WINDOW // 4)
carrier = np.tile(carrier, self.START_PATTERN_LENGTH)
zeroes = carrier * 0.0
signal = np.concatenate([zeroes, carrier])
signal = (2 ** 0.5) * signal / dsp.norm(signal)
@@ -86,9 +87,8 @@ class Detector(object):
coeffs = []
for i in range(len(buf) - len(signal)):
b = buf[i:i+len(signal)]
c = 0.0
if dsp.norm(b):
c = np.abs(np.dot(b, signal)) / dsp.norm(b)
norm_b = dsp.norm(b)
c = (np.abs(np.dot(b, signal)) / norm_b) if norm_b else 0.0
coeffs.append(c)
index = np.argmax(coeffs)