└── main.py


/main.py:
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  1 | import audioop
  2 | import ossaudiodev
  3 | from collections import deque
  4 | 
  5 | THRESHOLD_FACTOR = 3.5
  6 | FIRST_PEAK_FACTOR = 0.8
  7 | SECOND_PEAK_FACTOR = 0.5
  8 | 
  9 | def get_chunk(src, bias):
 10 |     data = audioop.bias(src.read(10000), 2, bias)
 11 |     return data, audioop.maxpp(data, 2)
 12 |     
 13 | def get_swipe(dev='/dev/audio'):
 14 |     audio = ossaudiodev.open(dev, 'r')
 15 |     audio.setparameters(ossaudiodev.AFMT_S16_LE, 1, 44100)
 16 |     
 17 |     baselines = deque([2**15] * 4)
 18 |     bias = 0
 19 |     while 1:
 20 |         data, power = get_chunk(audio, bias)
 21 |         
 22 |         baseline = sum(baselines) / len(baselines) * THRESHOLD_FACTOR
 23 |         print power, baseline, power / (baseline or 1)
 24 |         
 25 |         chunks = []
 26 |         while power > baseline:
 27 |             print power, baseline, power / (baseline or 1), '*'
 28 |             chunks.append(data)
 29 |             data, power = get_chunk(audio, bias)
 30 | 
 31 |         if len(chunks) > 1:
 32 |             data = old_data + ''.join(chunks) + data
 33 |             while audioop.maxpp(data[:3000], 2) < baseline / 2:
 34 |                 data = data[1000:]
 35 |             while audioop.maxpp(data[-3000:], 2) < baseline / 2:
 36 |                 data = data[:-1000]
 37 |             
 38 |             return audioop.bias(data, 2, -audioop.avg(data, 2))
 39 | 
 40 |         old_data = data
 41 |         
 42 |         bias = -audioop.avg(data, 2)
 43 |         
 44 |         baselines.popleft()
 45 |         baselines.append(power)
 46 | 
 47 | def get_samples(data, width=2):
 48 |     return list(audioop.getsample(data, width, i) for i in xrange(len(data) / width))
 49 | 
 50 | def get_peaks(data):
 51 |     peak_threshold = audioop.maxpp(data[:1000], 2) * FIRST_PEAK_FACTOR
 52 |     
 53 |     samples = get_samples(data)
 54 |     
 55 |     i = 0
 56 |     old_i = 0
 57 |     sign = 1
 58 |     while i < len(samples):
 59 |         peak = 0
 60 |         while samples[i] * sign > peak_threshold:
 61 |             peak = max(samples[i] * sign, peak)
 62 |             i += 1
 63 | 
 64 |         if peak:
 65 |             if old_i:
 66 |                 yield i - old_i
 67 |             old_i = i
 68 |             sign *= -1
 69 |             peak_threshold = peak * SECOND_PEAK_FACTOR
 70 |         
 71 |         i += 1
 72 | 
 73 | def get_bits(peaks):
 74 |     peaks = list(peaks)
 75 |     
 76 |     # Discard first 5 peaks
 77 |     peaks = peaks[5:]
 78 |     
 79 |     # Clock next 4 peaks (should be zeros)
 80 |     clocks = deque([p / 2.0 for p in peaks[:4]])
 81 |     
 82 |     i = 0
 83 |     while i < len(peaks)-2:
 84 |         peak = peaks[i]
 85 |         
 86 |         if peak > 1.5 * sum(clocks, 0.0) / len(clocks):
 87 |             yield 0
 88 |             i +=  1
 89 |             clocks.append(peak / 2)
 90 |         else:
 91 |             yield 1
 92 |             i += 2
 93 |             clocks.append(peak)
 94 |         clocks.popleft()
 95 |         
 96 | def get_bytes(bits, width=5):
 97 |     bits = list(bits)
 98 |     
 99 |     # Discard leading 0s
100 |     while bits[0] == 0:
101 |         bits = bits[1:]
102 |         
103 |     while 1:
104 |         byte, bits = bits[:width], bits[width:]
105 |         if len(byte) < width or sum(byte) % 2 != 1:
106 |             return 
107 |         yield byte
108 | 
109 | def bcd_chr(byte):
110 |     return chr(int(''.join(map(str, byte[-2::-1])), 2) + 48)
111 | 
112 | def get_bcd_chars(bytes):
113 |     bytes = list(bytes)
114 |     
115 |     
116 |     if bcd_chr(bytes[0]) != ';':
117 |         # Try reversed
118 |         bytes = [byte[::-1] for byte in reversed(bytes)]
119 |     
120 |     ibytes = iter(bytes)
121 |         
122 |     start = ibytes.next()
123 |     if bcd_chr(start) != ';':
124 |         raise DecodeError('No start sentinal')
125 |     
126 |     lrc = start
127 |     try:
128 |         while 1:
129 |             byte = ibytes.next()
130 |             char = bcd_chr(byte)
131 | 
132 |             for i in range(len(lrc) - 1):
133 |                 lrc[i] = (lrc[i] + byte[i]) % 2
134 | 
135 |             if char == '?':
136 |                 lrc[-1] = sum(lrc[:-1], 1) % 2
137 |                 real_lrc = ibytes.next()
138 |                 if real_lrc != lrc:
139 |                     raise DecodeError('Bad LRC')
140 |                 return
141 |                 
142 |             yield char
143 |                 
144 |     except StopIteration:
145 |         raise DecodeError('No end sentinal')
146 |                               
147 | 
148 | class DecodeError(Exception):
149 |     pass
150 | 
151 | if __name__ == '__main__':
152 |     print 'READY'
153 |     data = get_swipe()
154 |     peaks = list(get_peaks(data))
155 |     bits = list(get_bits(peaks))
156 |     bytes = list(get_bytes(bits))
157 |     try:
158 |         print ''.join(get_bcd_chars(bytes))
159 |     except DecodeError, e:
160 |         print e
161 | 


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