kopia lustrzana https://github.com/projecthorus/radiosonde_auto_rx
109 wiersze
3.3 KiB
Python
109 wiersze
3.3 KiB
Python
#!/usr/bin/env python
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#
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# Demodulator Performance Testing
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# Really simple testing of how the demodulators cope with added white noise.
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#
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# Copy in the relevant demod binaries to this directory.
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# Run with: python snr_test.py -f test_file.bin -d RS92
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#
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# The input test file should be the FM demodulated signal, with the sox post-processing.
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# For example:
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# RS92: rtl_fm -p 0 -M fm -F9 -s 12k -f 400500000 | sox -t raw -r 12k -e s -b 16 -c 1 - -r 48000 -b 8 -t wav - highpass 20 lowpass 2500 2>/dev/null > test_file.bin
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# RS41: rtl_fm -p 0 -M fm -F9 -s 15k -f 405500000 | sox -t raw -r 15k -e s -b 16 -c 1 - -r 48000 -b 8 -t wav - lowpass 2600 2>/dev/null > test_file.bin
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#
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# I'm unsure how comparable the RS92 and RS41 results are. Take the results with a healthy lump of salt.
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# At the very least, this should be useful to compare performance of different demod revisions.
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#
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import sys
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import os
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import numpy as np
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import argparse
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import subprocess
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# Demodulator calls. Replace as appropriate.
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RS92_DEMOD = "./rs92ecc --crc --ecc --vel"
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RS41_DEMOD = "./rs41ecc --crc --ecc --ptu"
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# Noise level range (gaussian distribution, standard deviation referred to full scale), in dB.
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# Both demods seem to fall over by -15 dB of added noise.
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NOISE_LEVELS = np.arange(-30.0, -15, 1.0)
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TEMP_FILENAME = 'temp.bin'
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def read_file(filename):
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''' Read in file and convert to floating point '''
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data = np.fromfile(filename,dtype='u1')
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header = data[:44] # This is a bit of a hack. The RS demods want a wave header, so we store this for later writeout.
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data = (data[44:].astype('float') - 128.0) / 128.0
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return (data,header)
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def write_file(filename, data, header):
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''' Convert an array of floats to uint8 and write to a file '''
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data = (data*128.0)+128.0
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data = data.astype('u1')
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f = open(filename,'wb')
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f.write(header.tobytes())
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f.write(data.tobytes())
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f.close()
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def add_noise(data, noise_level):
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''' Add white noise to a file '''
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noise_level_linear = 10**(noise_level/20.0)
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noise = np.random.normal(scale=noise_level_linear, size=data.shape)
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return data + noise
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def run_demod(filename, demod='RS92'):
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if demod == 'RS92':
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demod_bin = RS92_DEMOD
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else:
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demod_bin = RS41_DEMOD
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demod_command = "cat %s | %s" % (filename, demod_bin)
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# Run demod.
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with open(os.devnull, 'w') as devnull:
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output = subprocess.check_output(demod_command, shell=True, stderr=devnull)
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if demod == 'RS92':
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# RS92 demod just gives us one line per frame.
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return len(output.split('\n'))
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else:
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# RS41 demod gives us a lot more...
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frames = 0
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for _line in output.split('\n'):
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if _line != '':
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if _line[0] == '[':
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frames += 1
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return frames
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if __name__ == '__main__':
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# Command line arguments.
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parser = argparse.ArgumentParser()
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parser.add_argument("-f", "--filename", type=str, help="Input file. Assumed to be unsigned 8-bit, 48 kHz file.")
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parser.add_argument("-d", "--demod", type=str, help="Demodulator to test, either RS92 or RS41.")
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args = parser.parse_args()
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print("Reading: %s" % args.filename)
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# Read in input file.
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(data,header) = read_file(args.filename)
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print("Samples: %d" % len(data))
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for noise_lvl in NOISE_LEVELS:
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temp_data = add_noise(data, noise_lvl)
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write_file(TEMP_FILENAME, temp_data, header)
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frame_count = run_demod(TEMP_FILENAME, args.demod)
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print("%f dB: Frames Recovered: %d" % (noise_lvl,frame_count))
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