Pythonで、モールス符号の復号（２）

$ ~/anaconda3/bin/python test4.py ~/40wpm.wav 0 -1
 
<BT> 
NOW 
40 
WPM 
<BT> 
TEXT 
IS 
FROM 
JANUARY 
2014 
QST 
PAGE 
46
<BT> 
SETTING 
THE 
VFO. 
WITH 
THE 
TRANSMITTER 
OUTPUT 
CONNECTED 
TO 
A 
DUMMY 
LOAD, 
SET 
THE 
VFO 
TO 
THE 
CORRECT 
FREQUENCY 
FOR 
THE 
BAND 
OF 
INTEREST.

import sys
import numpy as np
import matplotlib.pyplot as plt
import soundfile as sf
from scipy.signal import hilbert

morse ={
	"" : "",
	"A" : ".-",
	"B" : "-...",
	"C" : "-.-.",
	"D" : "-..",
	"E" : ".",
	"F" : "..-.",
	"G" : "--.",
	"H" : "....",
	"I" : "..",
	"J" : ".---",
	"K" : "-.-",
	"L" : ".-..",
	"M" : "--",
	"N" : "-.",
	"O" : "---",
	"P" : ".--.",
	"Q" : "--.-",
	"R" : ".-.",
	"S" : "...",
	"T" : "-",
	"U" : "..-",
	"V" : "...-",
	"W" : ".--",
	"X" : "-..-",
	"Y" : "-.--",
	"Z" : "--..",
	"1" : ".----",
	"2" : "..---",
	"3" : "...--",
	"4" : "....-",
	"5" : ".....",
	"6" : "-....",
	"7" : "--...",
	"8" : "---..",
	"9" : "----.",
	"0" : "-----",
	"." : ".-.-.-",
	"," : "--..--",
	":" : "---...",
	"?" : "..--..",
	"'" : ".----.",
	"-" : "-....-",
	"/" : "-..-.",
	"@" : ".--.-.",
	"<BT>" : "-...-"
}

morse_inv = dict((v,k) for (k,v) in morse.items())

filename = sys.argv[1]
nstart   = int(sys.argv[2])
nframes  = int(sys.argv[3])

wav, fs  = sf.read(filename,start=nstart,frames=nframes)
analytic_signal = hilbert(wav)
env = np.abs(analytic_signal)

th = 0.5*max(env)
env[env<th] = 0
env[env!=0] = 1

t_up = 0
t_down = 0
up = []
down = []
string = ''
t_ws = 5000
t_ls = 2500
t_dd = 2500

for t in range(1, len(env-1)):
	if env[t-1] == 0 and env[t] == 1:
		t_up = t
		t_down_duration = t - t_down
		down.append(t_down_duration)
		if t_down_duration > t_ls:
			print(morse_inv[string], end='')
			string = ''
		if t_down_duration > t_ws:
			print(' ')
	if env[t-1] == 1 and env[t] == 0:
		t_down = t
		t_up_duration = t - t_up
		up.append(t_up_duration)
		if t_up_duration < t_dd:
			string = string + '.'
		else:
			string = string + '-'

print('')