radio-monitoring/barker/barker.py

#!/usr/bin/python3
'''
This script finds the barker code position in a WAV file
'''

from itertools import count
import argparse
from logging import getLogger, basicConfig

import numpy as np
import scipy.io.wavfile

BARKERS = {
    2: [1, -1],
    3: [1, 1, -1],
    4: [1, 1, -1, 1],
    5: [1, 1, 1, -1, 1],
    7: [1, 1, 1, -1, -1, 1, -1],
    11: [1, 1, 1, -1, -1, -1, 1, -1, -1, 1, -1],
    13: [1, 1, 1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1],
}


def get_parser():
    p = argparse.ArgumentParser()
    p.add_argument("fname")
    p.add_argument(
        "--barker-sequence-length", type=int, default=5, choices=BARKERS.keys()
    )
    p.add_argument(
        "--barker-freq-1", default=1000, type=int, help='Known as "+1" in barker code'
    )
    p.add_argument(
        "--barker-freq-2", default=500, type=int, help='Known as "-1" in barker code'
    )
    p.add_argument(
        "--log-level",
        default="WARNING",
        choices=["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"],
    )
    return p


def all_contigous_series(seq) -> list:
    """
    Put every element of seq into a list of all elements to which it is contigous.

    >>> all_contigous_series([1,2,10,11,12])
    [[1, 2], [10, 11, 12]]
    """

    out = [[]]
    for elem in seq:
        if not out[-1] or elem == out[-1][-1] + 1:
            out[-1].append(elem)
        else:
            assert len(out[-1]) > 0
            out.append([elem])
    if not out[-1]:
        out.pop()
    return out


def largest_contigous_series(seq) -> list:
    """
    Like all_contigous_series, but pick the biggest.

    >>> largest_contigous_series([1,2,10,11,12])
    [10, 11, 12]
    """

    return max(all_contigous_series(seq), key=len)


class SequenceOutOfBoundsException(IndexError):
    pass


class Barker:
    def __init__(
        self,
        barker_sequence,
        barker_freqs,
        framerate: int,
        wave,
        threshold=0,
        symbol_ms=100,
        chunks_per_symbol=10,
    ):
        self.barker = barker_sequence
        self.freqs = barker_freqs
        self.threshold = threshold
        self.framerate = framerate
        self.wave = wave
        self.log = getLogger(self.__class__.__name__)

        self.symbol_ms = symbol_ms
        self.chunks_per_symbol = chunks_per_symbol
        # how many millisecond is a chunk long
        self.chunk_ms = int(self.symbol_ms / self.chunks_per_symbol)

    def decode_symbol(self, data) -> int:
        """
        given some data, it will try to understand if that's a 1 or a -1
        """
        r = np.fft.fft(data, self.framerate)

        def to_int(val):
            return int(np.absolute(val))

        values = [to_int(r[freq]) for freq in self.freqs]
        if max(values) < self.threshold:
            return 0
        is_symbol_1 = values[0] > values[1]
        return 1 if is_symbol_1 else -1

    def analyze_sequence(self, start_chunk: int) -> float:
        frames_per_chunk = int(self.framerate * self.chunk_ms // 1000)
        frames_per_symbol = frames_per_chunk * self.chunks_per_symbol
        total_frames = frames_per_symbol * len(self.barker)
        symbol_start = start_chunk * frames_per_chunk
        sequence_end = symbol_start + total_frames
        if sequence_end > len(self.wave):
            raise SequenceOutOfBoundsException("Invalid start_chunk")
        fitness = 0

        # print()
        for symbol in self.barker:
            symbol_end = symbol_start + frames_per_symbol
            # print(symbol_start, symbol_end)
            to_analyze = self.wave[symbol_start:symbol_end]
            symbol_is = self.decode_symbol(to_analyze)

            # print('is', symbol_is, 'should', symbol)
            fitness += symbol_is * symbol

            symbol_start += frames_per_symbol
        return fitness

    def analyze(self):
        total = len(self.wave)
        self.log.debug("tot frames = %s", total)
        self.log.debug("framerate = %s", self.framerate)
        self.log.debug("duration = %.2fs", (total / self.framerate))

        bestvalue = None
        bestshifts = []
        for shift in count():
            try:
                val = self.analyze_sequence(shift)
            except SequenceOutOfBoundsException:
                break
            if (bestvalue is None) or (val > bestvalue):
                bestvalue = val
                bestshifts = [shift]
            elif val == bestvalue:
                bestshifts.append(shift)

        if bestvalue < int(len(self.barker) * 2 / 3):
            raise ValueError("Could not find the barker code")

        bestshifts = largest_contigous_series(bestshifts)
        self.log.debug(
            "largest contigous series of besthifts picked among %d", len(bestshifts)
        )
        bestshift = bestshifts[len(bestshifts) // 2]
        shift_ms = self.chunk_ms * bestshift
        shift_s = shift_ms / 1000.0
        self.log.info(
            "bestshift at chunk %d (%.2fs): %d", bestshift, shift_s, bestvalue
        )
        return (bestshift, shift_ms, bestvalue)


def main():
    args = get_parser().parse_args()
    basicConfig(level=args.log_level)
    framerate, data = scipy.io.wavfile.read(args.fname)
    if len(data.shape) > 1:
        raise ValueError("audio not mono maybe?")
        data = data[:, 0]

    barker_sequence = BARKERS[args.barker_sequence_length]
    barker = Barker(
        barker_sequence, [args.barker_freq_1, args.barker_freq_2], framerate, data
    )
    chunk, shift, fitness = barker.analyze()  # in milliseconds
    print(shift)


if __name__ == "__main__":
    main()