Example #1
0
class TestAudioManager(unittest.TestCase):
    def setUp(self):
        self.tb = gr.top_block()
        self.p = AudioManager(
            graph=self.tb,
            audio_config=None,
            stereo=False)

    def test_smoke(self):
        rs = self.p.reconnecting()
        rs.input(ConnectionCanarySource(self.tb), 10000, 'client')
        rs.finish_bus_connections()
        self.tb.start()
        self.tb.stop()
        self.tb.wait()

    def test_wrong_dest_name(self):
        """
        Shouldn't fail to construct a valid flow graph, despite the bad name.
        """
        rs = self.p.reconnecting()
        rs.input(ConnectionCanarySource(self.tb), 10000, 'bogusname')
        rs.finish_bus_connections()
        self.tb.start()
        self.tb.stop()
        self.tb.wait()
Example #2
0
    def __init__(self, devices={}, audio_config=None, features=_stub_features):
        if len(devices) <= 0:
            raise ValueError('Must have at least one RF device')
        
        gr.top_block.__init__(self, "SDR top block")
        self.__running = False  # duplicate of GR state we can't reach, see __start_or_stop
        self.__has_a_useful_receiver = False

        # Configuration
        # TODO: device refactoring: Remove vestigial 'accessories'
        self._sources = {k: d for k, d in devices.iteritems() if d.can_receive()}
        self._accessories = accessories = {k: d for k, d in devices.iteritems() if not d.can_receive()}
        self.source_name = self._sources.keys()[0]  # arbitrary valid initial value
        self.__rx_device_type = Enum({k: v.get_name() or k for (k, v) in self._sources.iteritems()})
        
        # Audio early setup
        self.__audio_manager = AudioManager(  # must be before contexts
            graph=self,
            audio_config=audio_config,
            stereo=features['stereo'])

        # Blocks etc.
        # TODO: device refactoring: remove 'source' concept (which is currently a device)
        # TODO: remove legacy no-underscore names, maybe get rid of self.source
        self.source = None
        self.__monitor_rx_driver = None
        self.monitor = MonitorSink(
            signal_type=SignalType(sample_rate=10000, kind='IQ'),  # dummy value will be updated in _do_connect
            context=Context(self))
        self.monitor.get_interested_cell().subscribe(self.__start_or_stop_later)
        self.__clip_probe = MaxProbe()
        
        # Receiver blocks (multiple, eventually)
        self._receivers = {}
        self._receiver_valid = {}
        
        # collections
        # TODO: No longer necessary to have these non-underscore names
        self.sources = CollectionState(self._sources)
        self.receivers = ReceiverCollection(self._receivers, self)
        self.accessories = CollectionState(accessories)
        self.__telemetry_store = TelemetryStore()
        
        # Flags, other state
        self.__needs_reconnect = [u'initialization']
        self.__in_reconnect = False
        self.receiver_key_counter = 0
        self.receiver_default_state = {}
        self.__cpu_calculator = LazyRateCalculator(lambda: time.clock())
        
        # Initialization
        
        def hookup_vfo_callback(k, d):  # function so as to not close over loop variable
            d.get_vfo_cell().subscribe(lambda: self.__device_vfo_callback(k))
        
        for k, d in devices.iteritems():
            hookup_vfo_callback(k, d)
        
        self._do_connect()
Example #3
0
File: top.py Project: nunb/shinysdr
    def __init__(self, devices={}, audio_config=None, stereo=True):
        if not len(devices) > 0:
            raise ValueError('Must have at least one RF device')
        
        gr.top_block.__init__(self, "SDR top block")
        self.__running = False  # duplicate of GR state we can't reach, see __start_or_stop
        self.__has_a_useful_receiver = False

        # Configuration
        # TODO: device refactoring: Remove vestigial 'accessories'
        self._sources = {k: d for k, d in devices.iteritems() if d.can_receive()}
        self._accessories = accessories = {k: d for k, d in devices.iteritems() if not d.can_receive()}
        self.source_name = self._sources.keys()[0]  # arbitrary valid initial value
        self.__rx_device_type = Enum({k: v.get_name() or k for (k, v) in self._sources.iteritems()})
        
        # Audio early setup
        self.__audio_manager = AudioManager(  # must be before contexts
            graph=self,
            audio_config=audio_config,
            stereo=stereo)

        # Blocks etc.
        # TODO: device refactoring: remove 'source' concept (which is currently a device)
        self.source = None
        self.__monitor_rx_driver = None
        self.monitor = MonitorSink(
            signal_type=SignalType(sample_rate=10000, kind='IQ'),  # dummy value will be updated in _do_connect
            context=Context(self))
        self.monitor.get_interested_cell().subscribe(self.__start_or_stop_later)
        self.__clip_probe = MaxProbe()
        
        # Receiver blocks (multiple, eventually)
        self._receivers = {}
        self._receiver_valid = {}
        
        self.__shared_objects = {}
        
        # kludge for using collection like block - TODO: better architecture
        self.sources = CollectionState(self._sources)
        self.receivers = ReceiverCollection(self._receivers, self)
        self.accessories = CollectionState(accessories)
        # TODO: better name than "shared objects"
        self.shared_objects = CollectionState(self.__shared_objects, dynamic=True)
        
        # Flags, other state
        self.__needs_reconnect = [u'initialization']
        self.__in_reconnect = False
        self.receiver_key_counter = 0
        self.receiver_default_state = {}
        self.__cpu_calculator = LazyRateCalculator(lambda: time.clock())
        
        # Initialization
        
        def hookup_vfo_callback(k, d):  # function so as to not close over loop variable
            d.get_vfo_cell().subscribe(lambda: self.__device_vfo_callback(k))
        
        for k, d in devices.iteritems():
            hookup_vfo_callback(k, d)
        
        self._do_connect()
Example #4
0
class TestAudioManager(unittest.TestCase):
    def setUp(self):
        self.tb = gr.top_block()
        self.p = AudioManager(graph=self.tb, audio_config=None, stereo=False)

    def test_smoke(self):
        rs = self.p.reconnecting()
        rs.input(ConnectionCanarySource(self.tb), 10000, 'client')
        rs.finish_bus_connections()
        self.tb.start()
        self.tb.stop()
        self.tb.wait()

    def test_wrong_dest_name(self):
        """
        Shouldn't fail to construct a valid flow graph, despite the bad name.
        """
        rs = self.p.reconnecting()
        rs.input(ConnectionCanarySource(self.tb), 10000, 'bogusname')
        rs.finish_bus_connections()
        self.tb.start()
        self.tb.stop()
        self.tb.wait()
Example #5
0
 def setUp(self):
     self.tb = gr.top_block()
     self.p = AudioManager(graph=self.tb, audio_config=None, stereo=False)
Example #6
0
File: top.py Project: nunb/shinysdr
class Top(gr.top_block, ExportedState, RecursiveLockBlockMixin):

    def __init__(self, devices={}, audio_config=None, stereo=True):
        if not len(devices) > 0:
            raise ValueError('Must have at least one RF device')
        
        gr.top_block.__init__(self, "SDR top block")
        self.__running = False  # duplicate of GR state we can't reach, see __start_or_stop
        self.__has_a_useful_receiver = False

        # Configuration
        # TODO: device refactoring: Remove vestigial 'accessories'
        self._sources = {k: d for k, d in devices.iteritems() if d.can_receive()}
        self._accessories = accessories = {k: d for k, d in devices.iteritems() if not d.can_receive()}
        self.source_name = self._sources.keys()[0]  # arbitrary valid initial value
        self.__rx_device_type = Enum({k: v.get_name() or k for (k, v) in self._sources.iteritems()})
        
        # Audio early setup
        self.__audio_manager = AudioManager(  # must be before contexts
            graph=self,
            audio_config=audio_config,
            stereo=stereo)

        # Blocks etc.
        # TODO: device refactoring: remove 'source' concept (which is currently a device)
        self.source = None
        self.__monitor_rx_driver = None
        self.monitor = MonitorSink(
            signal_type=SignalType(sample_rate=10000, kind='IQ'),  # dummy value will be updated in _do_connect
            context=Context(self))
        self.monitor.get_interested_cell().subscribe(self.__start_or_stop_later)
        self.__clip_probe = MaxProbe()
        
        # Receiver blocks (multiple, eventually)
        self._receivers = {}
        self._receiver_valid = {}
        
        self.__shared_objects = {}
        
        # kludge for using collection like block - TODO: better architecture
        self.sources = CollectionState(self._sources)
        self.receivers = ReceiverCollection(self._receivers, self)
        self.accessories = CollectionState(accessories)
        # TODO: better name than "shared objects"
        self.shared_objects = CollectionState(self.__shared_objects, dynamic=True)
        
        # Flags, other state
        self.__needs_reconnect = [u'initialization']
        self.__in_reconnect = False
        self.receiver_key_counter = 0
        self.receiver_default_state = {}
        self.__cpu_calculator = LazyRateCalculator(lambda: time.clock())
        
        # Initialization
        
        def hookup_vfo_callback(k, d):  # function so as to not close over loop variable
            d.get_vfo_cell().subscribe(lambda: self.__device_vfo_callback(k))
        
        for k, d in devices.iteritems():
            hookup_vfo_callback(k, d)
        
        self._do_connect()

    def add_receiver(self, mode, key=None, state=None):
        if len(self._receivers) >= 100:
            # Prevent storage-usage DoS attack
            raise Exception('Refusing to create more than 100 receivers')
        
        if key is not None:
            assert key not in self._receivers
        else:
            while True:
                key = base26(self.receiver_key_counter)
                self.receiver_key_counter += 1
                if key not in self._receivers:
                    break
        
        if len(self._receivers) > 0:
            arbitrary = self._receivers.itervalues().next()
            defaults = arbitrary.state_to_json()
        else:
            defaults = self.receiver_default_state
            
        combined_state = defaults.copy()
        if 'device_name' in combined_state: del combined_state['device_name']  # should not be overridden
        if state is not None: combined_state.update(state)
        
        facet = ContextForReceiver(self, key)
        receiver = Receiver(
            mode=mode,
            audio_channels=self.__audio_manager.get_channels(),
            device_name=self.source_name,
            audio_destination=self.__audio_manager.get_default_destination(),  # TODO match others
            context=facet,
        )
        receiver.state_from_json(combined_state)  # TODO: Use unserialize_exported_state
        facet._receiver = receiver
        self._receivers[key] = receiver
        self._receiver_valid[key] = False
        
        self.__needs_reconnect.append(u'added receiver ' + key)
        self._do_connect()

        # until _enabled, the facet ignores any reconnect/rebuild-triggering callbacks
        facet._enabled = True
        
        return (key, receiver)

    def delete_receiver(self, key):
        assert key in self._receivers
        receiver = self._receivers[key]
        
        # save defaults for use if about to become empty
        if len(self._receivers) == 1:
            self.receiver_default_state = receiver.state_to_json()
        
        del self._receivers[key]
        del self._receiver_valid[key]
        self.__needs_reconnect.append(u'removed receiver ' + key)
        self._do_connect()

    # TODO move these methods to a facet of AudioManager
    def add_audio_queue(self, queue, queue_rate):
        self.__audio_manager.add_audio_queue(queue, queue_rate)
        self.__needs_reconnect.append(u'added audio queue')
        self._do_connect()
        self.__start_or_stop()
    
    def remove_audio_queue(self, queue):
        self.__audio_manager.remove_audio_queue(queue)
        self.__start_or_stop()
        self.__needs_reconnect.append(u'removed audio queue')
        self._do_connect()
    
    def get_audio_queue_channels(self):
        '''
        Return the number of channels (which will be 1 or 2) in audio queue outputs.
        '''
        return self.__audio_manager.get_channels()

    def _do_connect(self):
        """Do all reconfiguration operations in the proper order."""

        if self.__in_reconnect:
            raise Exception('reentrant reconnect or _do_connect crashed')
        self.__in_reconnect = True
        
        t0 = time.time()
        if self.source is not self._sources[self.source_name]:
            log.msg('Flow graph: Switching RF device to %s' % (self.source_name))
            self.__needs_reconnect.append(u'switched device')

            this_source = self._sources[self.source_name]
            
            self.source = this_source
            self.__monitor_rx_driver = this_source.get_rx_driver()
            monitor_signal_type = self.__monitor_rx_driver.get_output_type()
            self.monitor.set_signal_type(monitor_signal_type)
            self.monitor.set_input_center_freq(this_source.get_freq())
            self.__clip_probe.set_window_and_reconnect(0.5 * monitor_signal_type.get_sample_rate())
        
        if self.__needs_reconnect:
            log.msg(u'Flow graph: Rebuilding connections because: %s' % (', '.join(self.__needs_reconnect),))
            self.__needs_reconnect = []
            
            self._recursive_lock()
            self.disconnect_all()
            
            self.connect(
                self.__monitor_rx_driver,
                self.monitor)
            self.connect(
                self.__monitor_rx_driver,
                self.__clip_probe)

            # Filter receivers
            audio_rs = self.__audio_manager.reconnecting()
            n_valid_receivers = 0
            for key, receiver in self._receivers.iteritems():
                self._receiver_valid[key] = receiver.get_is_valid()
                if not self._receiver_valid[key]:
                    continue
                if not self.__audio_manager.validate_destination(receiver.get_audio_destination()):
                    log.err('Flow graph: receiver audio destination %r is not available' % (receiver.get_audio_destination(),))
                    continue
                n_valid_receivers += 1
                if n_valid_receivers > 6:
                    # Sanity-check to avoid burning arbitrary resources
                    # TODO: less arbitrary constant; communicate this restriction to client
                    log.err('Flow graph: Refusing to connect more than 6 receivers')
                    break
                self.connect(self._sources[receiver.get_device_name()].get_rx_driver(), receiver)
                audio_rs.input(receiver, receiver.get_output_type().get_sample_rate(), receiver.get_audio_destination())
            
            self.__has_a_useful_receiver = audio_rs.finish_bus_connections()
            
            self._recursive_unlock()
            # (this is in an if block but it can't not execute if anything else did)
            log.msg('Flow graph: ...done reconnecting (%i ms).' % ((time.time() - t0) * 1000,))
            
            self.__start_or_stop_later()
        
        self.__in_reconnect = False

    def __device_vfo_callback(self, device_key):
        # Note that in addition to the flow graph delay, the callLater is also needed in order to ensure we don't do our reconfiguration in the middle of the source's own workings.
        reactor.callLater(
            self._sources[device_key].get_rx_driver().get_tune_delay(),
            self.__device_vfo_changed,
            device_key)

    def __device_vfo_changed(self, device_key):
        device = self._sources[device_key]
        freq = device.get_freq()
        if self.source is device:
            self.monitor.set_input_center_freq(freq)
        for rec_key, receiver in self._receivers.iteritems():
            if receiver.get_device_name() == device_key:
                receiver.changed_device_freq()
                self._update_receiver_validity(rec_key)
            # TODO: If multiple receivers change validity we'll do redundant reconnects in this loop; avoid that.

    def _update_receiver_validity(self, key):
        receiver = self._receivers[key]
        if receiver.get_is_valid() != self._receiver_valid[key]:
            self.__needs_reconnect.append(u'receiver %s validity changed' % (key,))
            self._do_connect()

    def state_def(self, callback):
        super(Top, self).state_def(callback)
        # TODO make this possible to be decorator style
        callback(BlockCell(self, 'monitor'))
        callback(BlockCell(self, 'sources'))
        callback(BlockCell(self, 'source', persists=False))
        callback(BlockCell(self, 'receivers'))
        callback(BlockCell(self, 'accessories', persists=False))
        callback(BlockCell(self, 'shared_objects'))

    def start(self, **kwargs):
        # trigger reconnect/restart notification
        self._recursive_lock()
        self._recursive_unlock()
        
        super(Top, self).start(**kwargs)
        self.__running = True

    def stop(self):
        super(Top, self).stop()
        self.__running = False

    def __start_or_stop(self):
        # TODO: We should also run if any of:
        #   there are any data-logging receivers (e.g. APRS, ADS-B)
        #       (requires becoming aware of no-audio receivers)
        #   a client is watching a receiver's cell-based outputs (e.g. VOR)
        #       (requires becoming aware of cell subscriptions)
        should_run = (
            self.__has_a_useful_receiver
            or self.monitor.get_interested_cell().get())
        if should_run != self.__running:
            if should_run:
                self.start()
            else:
                self.stop()
                self.wait()

    def __start_or_stop_later(self):
        reactor.callLater(0, self.__start_or_stop)

    def close_all_devices(self):
        '''Close all devices in preparation for a clean shutdown.
        
        Makes this top block unusable'''
        for device in self._sources.itervalues():
            device.close()
        for device in self._accessories.itervalues():
            device.close()
        self.stop()
        self.wait()

    @exported_value(type_fn=lambda self: self.__rx_device_type)
    def get_source_name(self):
        return self.source_name
    
    @setter
    def set_source_name(self, value):
        if value == self.source_name:
            return
        if value not in self._sources:
            raise ValueError('Source %r does not exist' % (value,))
        self.source_name = value
        self._do_connect()
    
    @exported_value(type=Notice(always_visible=False))
    def get_clip_warning(self):
        level = self.__clip_probe.level()
        # We assume that our sample source's absolute limits on I and Q values are the range -1.0 to 1.0. This is a square region; therefore the magnitude observed can be up to sqrt(2) = 1.414 above this, allowing us some opportunity to measure the amount of excess, and also to detect clipping even if the device doesn't produce exactly +-1.0 valus.
        if level >= 1.0:
            return u'Input amplitude too high (%.2f \u2265 1.0). Reduce gain.' % math.sqrt(level)
        else:
            return u''
    
    # TODO: This becomes useless w/ Session fix
    @exported_value(type=float)
    def get_cpu_use(self):
        return round(self.__cpu_calculator.get(), 2)
    
    def get_shared_object(self, ctor):
        # TODO: Make shared objects able to persist. This will probably require some kind of up-front registry.
        # TODO: __name__ is a lousy strategy
        key = ctor.__name__
        if key not in self.__shared_objects:
            self.__shared_objects[key] = ctor()
        return self.__shared_objects[key]
    
    def _get_rx_device_type(self):
        '''for ContextForReceiver only'''
        return self.__rx_device_type
    
    def _get_audio_destination_type(self):
        '''for ContextForReceiver only'''
        return self.__audio_manager.get_destination_type()
    
    def _trigger_reconnect(self, reason):
        self.__needs_reconnect.append(reason)
        self._do_connect()
    
    def _recursive_lock_hook(self):
        for source in self._sources.itervalues():
            source.notify_reconnecting_or_restarting()
Example #7
0
 def setUp(self):
     self.tb = gr.top_block()
     self.p = AudioManager(
         graph=self.tb,
         audio_config=None,
         stereo=False)
Example #8
0
class Top(gr.top_block, ExportedState, RecursiveLockBlockMixin):

    def __init__(self, devices={}, audio_config=None, features=_stub_features):
        if len(devices) <= 0:
            raise ValueError('Must have at least one RF device')
        
        gr.top_block.__init__(self, "SDR top block")
        self.__running = False  # duplicate of GR state we can't reach, see __start_or_stop
        self.__has_a_useful_receiver = False

        # Configuration
        # TODO: device refactoring: Remove vestigial 'accessories'
        self._sources = {k: d for k, d in devices.iteritems() if d.can_receive()}
        self._accessories = accessories = {k: d for k, d in devices.iteritems() if not d.can_receive()}
        self.source_name = self._sources.keys()[0]  # arbitrary valid initial value
        self.__rx_device_type = Enum({k: v.get_name() or k for (k, v) in self._sources.iteritems()})
        
        # Audio early setup
        self.__audio_manager = AudioManager(  # must be before contexts
            graph=self,
            audio_config=audio_config,
            stereo=features['stereo'])

        # Blocks etc.
        # TODO: device refactoring: remove 'source' concept (which is currently a device)
        # TODO: remove legacy no-underscore names, maybe get rid of self.source
        self.source = None
        self.__monitor_rx_driver = None
        self.monitor = MonitorSink(
            signal_type=SignalType(sample_rate=10000, kind='IQ'),  # dummy value will be updated in _do_connect
            context=Context(self))
        self.monitor.get_interested_cell().subscribe(self.__start_or_stop_later)
        self.__clip_probe = MaxProbe()
        
        # Receiver blocks (multiple, eventually)
        self._receivers = {}
        self._receiver_valid = {}
        
        # collections
        # TODO: No longer necessary to have these non-underscore names
        self.sources = CollectionState(self._sources)
        self.receivers = ReceiverCollection(self._receivers, self)
        self.accessories = CollectionState(accessories)
        self.__telemetry_store = TelemetryStore()
        
        # Flags, other state
        self.__needs_reconnect = [u'initialization']
        self.__in_reconnect = False
        self.receiver_key_counter = 0
        self.receiver_default_state = {}
        self.__cpu_calculator = LazyRateCalculator(lambda: time.clock())
        
        # Initialization
        
        def hookup_vfo_callback(k, d):  # function so as to not close over loop variable
            d.get_vfo_cell().subscribe(lambda: self.__device_vfo_callback(k))
        
        for k, d in devices.iteritems():
            hookup_vfo_callback(k, d)
        
        self._do_connect()

    def add_receiver(self, mode, key=None, state=None):
        if len(self._receivers) >= 100:
            # Prevent storage-usage DoS attack
            raise Exception('Refusing to create more than 100 receivers')
        
        if key is not None:
            assert key not in self._receivers
        else:
            while True:
                key = base26(self.receiver_key_counter)
                self.receiver_key_counter += 1
                if key not in self._receivers:
                    break
        
        if len(self._receivers) > 0:
            arbitrary = self._receivers.itervalues().next()
            defaults = arbitrary.state_to_json()
        else:
            defaults = self.receiver_default_state
            
        combined_state = defaults.copy()
        for do_not_use_default in ['device_name', 'freq_linked_to_device']:
            if do_not_use_default in combined_state:
                del combined_state[do_not_use_default]
        if state is not None:
            combined_state.update(state)
        
        facet = ContextForReceiver(self, key)
        receiver = unserialize_exported_state(Receiver, kwargs=dict(
            mode=mode,
            audio_channels=self.__audio_manager.get_channels(),
            device_name=self.source_name,
            audio_destination=self.__audio_manager.get_default_destination(),  # TODO match others
            context=facet,
        ), state=combined_state)
        facet._receiver = receiver
        self._receivers[key] = receiver
        self._receiver_valid[key] = False
        
        self.__needs_reconnect.append(u'added receiver ' + key)
        self._do_connect()

        # until _enabled, the facet ignores any reconnect/rebuild-triggering callbacks
        facet._enabled = True
        
        return (key, receiver)

    def delete_receiver(self, key):
        assert key in self._receivers
        receiver = self._receivers[key]
        
        # save defaults for use if about to become empty
        if len(self._receivers) == 1:
            self.receiver_default_state = receiver.state_to_json()
        
        del self._receivers[key]
        del self._receiver_valid[key]
        self.__needs_reconnect.append(u'removed receiver ' + key)
        self._do_connect()

    # TODO move these methods to a facet of AudioManager
    def add_audio_queue(self, queue, queue_rate):
        self.__audio_manager.add_audio_queue(queue, queue_rate)
        self.__needs_reconnect.append(u'added audio queue')
        self._do_connect()
        self.__start_or_stop()
    
    def remove_audio_queue(self, queue):
        self.__audio_manager.remove_audio_queue(queue)
        self.__start_or_stop()
        self.__needs_reconnect.append(u'removed audio queue')
        self._do_connect()
    
    def get_audio_queue_channels(self):
        """
        Return the number of channels (which will be 1 or 2) in audio queue outputs.
        """
        return self.__audio_manager.get_channels()

    def _do_connect(self):
        """Do all reconfiguration operations in the proper order."""

        if self.__in_reconnect:
            raise Exception('reentrant reconnect or _do_connect crashed')
        self.__in_reconnect = True
        
        t0 = time.time()
        if self.source is not self._sources[self.source_name]:
            log.msg('Flow graph: Switching RF device to %s' % (self.source_name))
            self.__needs_reconnect.append(u'switched device')

            this_source = self._sources[self.source_name]
            
            self.source = this_source
            self.__monitor_rx_driver = this_source.get_rx_driver()
            monitor_signal_type = self.__monitor_rx_driver.get_output_type()
            self.monitor.set_signal_type(monitor_signal_type)
            self.monitor.set_input_center_freq(this_source.get_freq())
            self.__clip_probe.set_window_and_reconnect(0.5 * monitor_signal_type.get_sample_rate())
        
        if self.__needs_reconnect:
            log.msg(u'Flow graph: Rebuilding connections because: %s' % (', '.join(self.__needs_reconnect),))
            self.__needs_reconnect = []
            
            self._recursive_lock()
            self.disconnect_all()
            
            self.connect(
                self.__monitor_rx_driver,
                self.monitor)
            self.connect(
                self.__monitor_rx_driver,
                self.__clip_probe)

            # Filter receivers
            audio_rs = self.__audio_manager.reconnecting()
            n_valid_receivers = 0
            has_non_audio_receiver = False
            for key, receiver in self._receivers.iteritems():
                self._receiver_valid[key] = receiver.get_is_valid()
                if not self._receiver_valid[key]:
                    continue
                if not self.__audio_manager.validate_destination(receiver.get_audio_destination()):
                    log.err('Flow graph: receiver audio destination %r is not available' % (receiver.get_audio_destination(),))
                    continue
                n_valid_receivers += 1
                if n_valid_receivers > 6:
                    # Sanity-check to avoid burning arbitrary resources
                    # TODO: less arbitrary constant; communicate this restriction to client
                    log.err('Flow graph: Refusing to connect more than 6 receivers')
                    break
                self.connect(self._sources[receiver.get_device_name()].get_rx_driver(), receiver)
                receiver_output_type = receiver.get_output_type()
                if receiver_output_type.get_sample_rate() <= 0:
                    # Demodulator has no output, but receiver has a dummy output, so connect it to something to satisfy flow graph structure.
                    for ch in xrange(0, self.__audio_manager.get_channels()):
                        self.connect((receiver, ch), blocks.null_sink(gr.sizeof_float))
                    # Note that we have a non-audio receiver which may be useful even if there is no audio output
                    has_non_audio_receiver = True
                else:
                    assert receiver_output_type.get_kind() == 'STEREO'
                    audio_rs.input(receiver, receiver_output_type.get_sample_rate(), receiver.get_audio_destination())
            
            self.__has_a_useful_receiver = audio_rs.finish_bus_connections() or \
                has_non_audio_receiver
            
            self._recursive_unlock()
            # (this is in an if block but it can't not execute if anything else did)
            log.msg('Flow graph: ...done reconnecting (%i ms).' % ((time.time() - t0) * 1000,))
            
            self.__start_or_stop_later()
        
        self.__in_reconnect = False

    def __device_vfo_callback(self, device_key):
        # Note that in addition to the flow graph delay, the callLater is also needed in order to ensure we don't do our reconfiguration in the middle of the source's own workings.
        reactor.callLater(
            self._sources[device_key].get_rx_driver().get_tune_delay(),
            self.__device_vfo_changed,
            device_key)

    def __device_vfo_changed(self, device_key):
        device = self._sources[device_key]
        freq = device.get_freq()
        if self.source is device:
            self.monitor.set_input_center_freq(freq)
        for rec_key, receiver in self._receivers.iteritems():
            if receiver.get_device_name() == device_key:
                receiver.changed_device_freq()
                self._update_receiver_validity(rec_key)
            # TODO: If multiple receivers change validity we'll do redundant reconnects in this loop; avoid that.

    def _update_receiver_validity(self, key):
        receiver = self._receivers[key]
        if receiver.get_is_valid() != self._receiver_valid[key]:
            self.__needs_reconnect.append(u'receiver %s validity changed' % (key,))
            self._do_connect()
    
    @exported_block()
    def get_monitor(self):
        return self.monitor
    
    @exported_block(persists=False)
    def get_sources(self):
        return self.sources
    
    @exported_block(persists=False)
    def get_source(self):
        return self.source  # TODO no need for this now...?
    
    @exported_block()
    def get_receivers(self):
        return self.receivers
    
    @exported_block(persists=False)
    def get_accessories(self):
        return self.accessories
    
    @exported_block()
    def get_telemetry_store(self):
        return self.__telemetry_store
    
    def start(self, **kwargs):
        # trigger reconnect/restart notification
        self._recursive_lock()
        self._recursive_unlock()
        
        super(Top, self).start(**kwargs)
        self.__running = True

    def stop(self):
        super(Top, self).stop()
        self.__running = False

    def __start_or_stop(self):
        # TODO: Improve start/stop conditions:
        #
        # * run if a client is watching an audio-having receiver's cell-based outputs (e.g. VOR) but not listening to audio
        #
        # * don't run if no client is watching a pure telemetry receiver
        #   (maybe a user preference since having a history when you connect is useful)
        #
        # Both of these refinements require becoming aware of cell subscriptions.
        should_run = (
            self.__has_a_useful_receiver
            or self.monitor.get_interested_cell().get())
        if should_run != self.__running:
            if should_run:
                self.start()
            else:
                self.stop()
                self.wait()

    def __start_or_stop_later(self):
        reactor.callLater(0, self.__start_or_stop)

    def close_all_devices(self):
        """Close all devices in preparation for a clean shutdown.
        
        Makes this top block unusable"""
        for device in self._sources.itervalues():
            device.close()
        for device in self._accessories.itervalues():
            device.close()
        self.stop()
        self.wait()

    @exported_value(type_fn=lambda self: self.__rx_device_type)
    def get_source_name(self):
        return self.source_name
    
    @setter
    def set_source_name(self, value):
        if value == self.source_name:
            return
        if value not in self._sources:
            raise ValueError('Source %r does not exist' % (value,))
        self.source_name = value
        self._do_connect()
    
    @exported_value(type=Notice(always_visible=False))
    def get_clip_warning(self):
        level = self.__clip_probe.level()
        # We assume that our sample source's absolute limits on I and Q values are the range -1.0 to 1.0. This is a square region; therefore the magnitude observed can be up to sqrt(2) = 1.414 above this, allowing us some opportunity to measure the amount of excess, and also to detect clipping even if the device doesn't produce exactly +-1.0 valus.
        if level >= 1.0:
            return u'Input amplitude too high (%.2f \u2265 1.0). Reduce gain.' % math.sqrt(level)
        else:
            return u''
    
    # TODO: This becomes useless w/ Session fix
    @exported_value(type=float)
    def get_cpu_use(self):
        return round(self.__cpu_calculator.get(), 2)
    
    def _get_rx_device_type(self):
        """for ContextForReceiver only"""
        return self.__rx_device_type
    
    def _get_audio_destination_type(self):
        """for ContextForReceiver only"""
        return self.__audio_manager.get_destination_type()
    
    def _trigger_reconnect(self, reason):
        self.__needs_reconnect.append(reason)
        self._do_connect()
    
    def _recursive_lock_hook(self):
        for source in self._sources.itervalues():
            source.notify_reconnecting_or_restarting()