add a sample non-OL dynamic random experiment

flyvr.exe --config rig.yml -p playlists\audio_daq_paused.yml -e experiments\paired_random_audio_daq.py

this starts a python experiment which randomly chooses
corresponding pairs (in the order they were written in the
playlist) from the audio and daq backend, and plays them
simultaenously.

note: the rig.yml configuration file should have
 * the audio_in and audio_out channels defined
 * you should disable the next signaling with
   remote_2P_next_disable

experiments/paired_random_audio_daq.py

@@ -0,0 +1,50 @@
+import time
+import random
+
+from flyvr.control.experiment import Experiment
+
+# this experiment randomly chooses only corresponding playlist items across
+# the audio and daq backend. for example, if the daq playlist as items with
+# identifiers 'd1', 'd2', 'd3', and 'd4', and the audio playlist has items
+# with identifiers 'a1', 'a2', and 'a3', then every SWITCH_SECONDS we random
+# choose to play simultaneously only (`d1' and 'a1'), ('d2' and 'a2'), or
+# ('d3' and 'a3')
+
+SWITCH_SECONDS = 5
+
+
+class _MyExperiment(Experiment):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._exp_started = False
+        self._last_switch = None
+        self._n_common_playlist_items = 0
+
+    def process_state(self, state):
+        if self._exp_started:
+            t = time.time()
+            if (t - self._last_switch) > SWITCH_SECONDS:
+                idx = random.randint(0, self._n_common_playlist_items - 1)
+
+                item_daq = self.configured_playlist_items[Experiment.BACKEND_DAQ][idx]
+                self.play_playlist_item(Experiment.BACKEND_DAQ, item_daq)
+                item_audio = self.configured_playlist_items[Experiment.BACKEND_AUDIO][idx]
+                self.play_playlist_item(Experiment.BACKEND_AUDIO, item_audio)
+
+                self.log.info('switched to daq:%s and audio:%s' % (item_daq, item_audio))
+
+                self._last_switch = t
+        else:
+            if self.is_started() and \
+                    self.is_backend_ready(Experiment.BACKEND_AUDIO) and \
+                    self.is_backend_ready(Experiment.BACKEND_DAQ):
+                self._exp_started = True
+                self._last_switch = time.time() - SWITCH_SECONDS  # switch next loop
+
+            self._n_common_playlist_items = min(len(self.configured_playlist_items[Experiment.BACKEND_DAQ]),
+                                                len(self.configured_playlist_items[Experiment.BACKEND_AUDIO]))
+            assert self._n_common_playlist_items > 0
+
+
+experiment = _MyExperiment()

playlists/audio_daq_paused.yml

@@ -0,0 +1,13 @@
+playlist:
+  daq:
+    - _options: {random_mode: 'none', paused: true}
+    - sq20hz: {name: 'square', sample_rate: 10000, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 20, max_value: 10.0, min_value: -10.0, amplitude: 2.0, phase: 0.0}
+    - sq40hz: {name: 'square', sample_rate: 10000, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 40, max_value: 10.0, min_value: -10.0, amplitude: 4.0, phase: 0.0}
+    - sq60hz: {name: 'square', sample_rate: 10000, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 60, max_value: 10.0, min_value: -10.0, amplitude: 6.0, phase: 0.0}
+    - sq80hz: {name: 'square', sample_rate: 10000, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 80, max_value: 10.0, min_value: -10.0, amplitude: 8.0, phase: 0.0}
+  audio:
+    - _options: {random_mode: 'none', paused: true}
+    - sin200hz: {name: 'sin', sample_rate: 44100, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 200, max_value: 10.0, min_value: -10.0, amplitude: 1.0, phase: 0.0}
+    - sin400hz: {name: 'sin', sample_rate': 44100, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 400, max_value: 10.0, min_value: -10.0, amplitude: 1.0, phase: 0.0}
+    - sin600hz: {name: 'sin', sample_rate: 44100, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 600, max_value: 10.0, min_value: -10.0, amplitude: 1.0, phase: 0.0}
+    - sin800hz: {name: 'sin', sample_rate: 44100, duration: 1000, pre_silence: 0, post_silence: 500, attenuator: null, frequency: 800, max_value: 10.0, min_value: -10.0, amplitude: 1.0, phase: 0.0}