#!/usr/bin/env python3
#
# SPDX-License-Identifier: GPL-3.0
#
# GNU Radio Python Flow Graph
# Title: FM Radio Receiver

import gnuradio.analog
import gnuradio.audio
import gnuradio.fft
import gnuradio.filter
import gnuradio.gr
import osmosdr


class fm_radio(gnuradio.gr.top_block):
    def __init__(self):
        gnuradio.gr.top_block.__init__(self, "FM Radio Receiver", catch_exceptions=True)

        samp_rate = 2560000
        channel_width_hertz = 250000
        audio_sample_rate_hertz = 48000

        rtlsdr_source = osmosdr.source()
        rtlsdr_source.set_sample_rate(samp_rate)
        rtlsdr_source.set_center_freq((98.3 * 1e6), 0)
        resampler = gnuradio.filter.rational_resampler_fff(
            interpolation=audio_sample_rate_hertz, decimation=channel_width_hertz
        )
        low_pass_filter = gnuradio.filter.fir_filter_ccf(
            samp_rate // channel_width_hertz,
            gnuradio.filter.firdes.low_pass(
                2, samp_rate, 100000, 10000, gnuradio.fft.window.WIN_KAISER, 6.76
            ),
        )
        audio_sink = gnuradio.audio.sink(audio_sample_rate_hertz)
        wbfm_demodulator = gnuradio.analog.wfm_rcv(
            quad_rate=channel_width_hertz, audio_decimation=1
        )

        self.connect((wbfm_demodulator, 0), (resampler, 0))
        self.connect((low_pass_filter, 0), (wbfm_demodulator, 0))
        self.connect((resampler, 0), (audio_sink, 0))
        self.connect((rtlsdr_source, 0), (low_pass_filter, 0))


def _main():
    top_block = fm_radio()
    top_block.start()
    input("Press Enter to quit: ")
    top_block.stop()
    top_block.wait()


if __name__ == "__main__":
    _main()