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precalculate additive noise

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This commit is contained in:
András Veres-Szentkirályi 2013-07-01 20:36:28 +02:00
parent ee803f0294
commit 30ec459a22
1 changed files with 4 additions and 3 deletions
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7
pysstv/sstv.py
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@ -4,7 +4,7 @@ from __future__ import division, with_statement
from math import sin, pi, floor
from random import random
from contextlib import closing
from itertools import imap
from itertools import imap, izip, cycle
from array import array
import wave
@ -58,8 +58,9 @@ class SSTV(object):
lowest = -amp
highest = amp - 1
chans = range(self.nchannels)
for value in self.gen_values():
sample = int(round(value * amp + alias * (random() - 0.5)))
alias_cycle = cycle((alias * (random() - 0.5) for _ in xrange(1024)))
for value, alias_item in izip(self.gen_values(), alias_cycle):
sample = int(round(value * amp + alias_item))
for chan in chans:
yield (lowest if sample <= lowest else
sample if sample <= highest else highest)