sdrplay-fm-radio/radio.py

from threading import Thread
import SoapySDR as soapy
import prefixed
from formats import *
import sys
import subprocess
import struct
from soapyhelpers import *
from samplerates import *


class Radio:
    FORMAT = 'CS16'
    SAMPLES = 8192
    PORT = 8554

    def __init__(self, name, device_info):
        self.name = name
        self.device_info = device_info
        self.run = False
        self.thread = None

        self.device = soapy.Device(device_info)
        if self.device is None:
            raise RuntimeError("Failed to connect to radio device")

        self.capabilities = self._get_capabilities()

    def configure(self, frequency):
        if self.is_streaming():
            raise RuntimeError("Cannot configure radio while a stream is active")

        frequency = int(prefixed.Float(frequency))
        bandwidth = 200000

        sample_rates = preferred_sample_rates(self.capabilities['rx']['sample-rates'])
        if len(sample_rates) == 0:
            raise RuntimeError("No suitable sample rates are available")
        self.sample_rate, self.output_rate = sample_rates[0]

        self.device.setFrequency(soapy.SOAPY_SDR_RX, 0, frequency)
        self.device.setSampleRate(soapy.SOAPY_SDR_RX, 0, self.sample_rate)
        self.device.setBandwidth(soapy.SOAPY_SDR_RX, 0, bandwidth)

        # Set automatic gain
        self.device.setGainMode(soapy.SOAPY_SDR_RX, 0, True)

        return {
            'frequency': self.device.getFrequency(soapy.SOAPY_SDR_RX, 0),
            'sample-rate': self.device.getSampleRate(soapy.SOAPY_SDR_RX, 0),
            'bandwidth': self.device.getBandwidth(soapy.SOAPY_SDR_RX, 0),
            'gain-mode': 'auto' if self.device.getGainMode(soapy.SOAPY_SDR_RX, 0) else 'manual',
        }

    def get_info(self):
        return {
            'name': self.name,
            'device': self.device_info,
            'capabilities': self.capabilities,
            'stream-path': self._stream_path(),
            'streaming': self.is_streaming(),
        }

    def _get_capabilities(self):
        def get_direction_capabilities(direction):
            return {
                'antennas': self.device.listAntennas(direction, 0),
                'gains': self.device.listGains(direction, 0),
                'frequencies': self.device.listFrequencies(direction, 0),
                'sample-rates': self.device.listSampleRates(direction, 0),
                'bandwidths': self.device.listBandwidths(direction, 0),
                'sensors': self.device.listSensors(direction, 0),
                'formats': self.device.getStreamFormats(direction, 0),
            }

        return {
            'rx': get_direction_capabilities(soapy.SOAPY_SDR_RX),
            'tx': get_direction_capabilities(soapy.SOAPY_SDR_TX),
            'clock-sources': self.device.listClockSources(),
            'time-sources': self.device.listTimeSources(),
            'register-interfaces': self.device.listRegisterInterfaces(),
            'gpios': self.device.listGPIOBanks(),
            'uarts': self.device.listUARTs(),
        }

    def is_streaming(self):
        return True if (self.thread and self.thread.is_alive()) else False

    def start_stream(self):
        if self.is_streaming():
            raise RuntimeError('Stream thread is already running')

        self.run = True
        self.thread = Thread(target=self._stream_thread, daemon=True, args=())
        self.thread.start()

    def end_stream(self):
        if self.thread is None:
            raise RuntimeError('No stream thread to terminate')

        self.run = False
        self.thread.join()
        self.thread = None

    def _stream_thread(self):
        self._init_stream()

        def is_alive(subprocess):
            return (subprocess.poll() is None)

        while self.run:
            # Check that the child processes are still running
            if (not is_alive(self.demod)) or (not is_alive(self.playback)):
                print('DSP chain failed, aborting stream.', file=sys.stderr)
                break

            result = self.device.readStream(self.stream, [self.buffer], Radio.SAMPLES)

            if result == 0:
                continue
            elif result.ret < 0:
                error = SoapyError(result.ret)
                if error is not SoapyError.Timeout:
                    print("Stream read failed, aborting stream:", error, file=sys.stderr)
                    break
                continue
            else:
                read_size = int(result.ret * 2)
                self.demod.stdin.write(
                    struct.pack(FORMATS[Radio.FORMAT].packing % read_size,
                    *self.buffer[:read_size])
                )

        self._cleanup_stream()

    def _init_stream(self):
        self.playback = subprocess.Popen(
            [
                '/usr/bin/ffmpeg', '-f', 's16le', '-ar', str(self.output_rate), '-ac', '2', '-i', '-',
                '-f', 'rtsp', f"rtsp://localhost{self._stream_path()}"
            ],
            stdin=subprocess.PIPE,
            stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL
        )

        self.demod = subprocess.Popen(
            ['/usr/bin/python3', 'fm_demod.py', '-f', 'CS16', '-s', str(self.sample_rate), '-d', str(self.output_rate)],
            stdin=subprocess.PIPE,
            stdout=self.playback.stdin,
            stderr=subprocess.DEVNULL
        )

        self.buffer = np.array([0] * Radio.SAMPLES * 2, FORMATS[Radio.FORMAT].numpy)
        self.stream = self.device.setupStream(soapy.SOAPY_SDR_RX, FORMATS[Radio.FORMAT].soapy)
        result = self.device.activateStream(self.stream)

        if result != 0:
            raise RuntimeError(f"Error activating stream: {result}")

    def _cleanup_stream(self):
        self.run = False

        # Cleanup the streaming objects in the reverse order to the _init method.
        self.device.deactivateStream(self.stream)
        self.device.closeStream(self.stream)
        self.buffer = None

        # .terminate()/.kill() followed by .wait() is required to properly clear
        # killed zombie processes from the process table.
        # https://stackoverflow.com/a/41961462
        self.demod.kill()
        self.demod.wait()
        self.demod = None
        self.playback.kill()
        self.playback.wait()
        self.playback = None

    def _stream_path(self):
        return f":{Radio.PORT}/radio/{self.name}"


"""
Quick and dirty test of the Radio class.
"""
if __name__ == '__main__':
    import time

    sdr = Radio('demo', {'driver': 'sdrplay'})

    print('Configuring...')
    sdr.configure('105.5M')
    print('Configured.')

    print('Starting stream...')
    sdr.start_stream()
    print('Stream started.')

    # Let the stream play for a while
    time.sleep(15)

    print('Ending stream...')
    sdr.end_stream()
    print('Stream ended.')