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added command line option parsing 

git-svn-id: http://op25.osmocom.org/svn/trunk@17 65a5c917-d112-43f1-993d-58c26a4786be
This commit is contained in:
mossmann 2008-04-05 17:25:47 +00:00
parent 747d4a7d88
commit 398cc0ee2f
1 changed files with 15 additions and 10 deletions
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25
python/c4fm-decode.py
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@ -1,19 +1,24 @@
#!/usr/bin/python
import struct, sys
from gnuradio.eng_option import eng_option
from optparse import OptionParser
"""
prototype P25 frame decoder
input: short 48 ksps frequency demodulated signal capture including at least one frame
(output of c4fm_demod.py)
input: short frequency demodulated signal capture including at least one frame (output of c4fm_demod.py)
output: symbols of a single frame (plus some excess)
"""
samples_per_symbol = 10
parser = OptionParser(option_class=eng_option)
parser.add_option("-i", "--input-file", type="string", default="demod.dat", help="specify the input file")
parser.add_option("-s", "--samples-per-symbol", type="int", default=10, help="samples per symbol of the input file")
(options, args) = parser.parse_args()
# frame synchronization header (in form most useful for correlation)
frame_sync = [1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, -1, -1, -1, 1, -1, 1, -1, -1, -1, -1, -1]
minimum_span = 5 # minimum number of adjacent correlations required to convince us
data = open('demod').read()
data = open(options.input_file).read()
input_samples = struct.unpack('f1'*(len(data)/4), data)
sync_samples = [] # subset of input samples synchronized with respect to frame sync
symbols = [] # recovered symbols (including frame sync)
@ -39,10 +44,10 @@ first = 0
last = 0
interesting = 0
correlation_threshold = len(frame_sync) * mean_deviation
for i in range(len(input_samples) - len(frame_sync) * samples_per_symbol):
for i in range(len(input_samples) - len(frame_sync) * options.samples_per_symbol):
correlation = 0
for j in range(len(frame_sync)):
correlation += frame_sync[j] * (input_samples[i + j * samples_per_symbol] - mean_value)
correlation += frame_sync[j] * (input_samples[i + j * options.samples_per_symbol] - mean_value)
#print i, correlation
if interesting:
if correlation < correlation_threshold:
@ -61,13 +66,13 @@ if last:
# use center point of several adjacent correlations
center = first + ((last - first) // 2)
# grab samples for symbol thereafter
for i in range(center, len(input_samples), samples_per_symbol):
for i in range(center, len(input_samples), options.samples_per_symbol):
# "integrate and dump"
# Add up several (samples_per_symbol) adjacent samples to create a single
# (downsampled) sample as specified by the P25 CAI standard.
total = 0.0
start = i - (samples_per_symbol/2)
end = i + 1 + (samples_per_symbol/2)
start = i - (options.samples_per_symbol/2)
end = i + 1 + (options.samples_per_symbol/2)
for sample in input_samples[start:end]: total += sample
sync_samples.append(total)
#print i, sync_samples[-1]