Commit 482d033f authored by Marios Fanourakis's avatar Marios Fanourakis

initial base version to work on

parent 2b8605d2
# LSL streams visualization
This python script visualizes all channels of selected LSL inlets in separate plots for quick verification of signal integrity.
## Requirements
Python 3.x:
* pylsl
* pyqtgraph
* QT5
\ No newline at end of file
#!/usr/bin/env python
ReceiveAndPlot example for LSL
This example shows data from all found outlets in realtime.
It illustrates the following use cases:
- efficiently pulling data, re-using buffers
- automatically discarding older samples
- online postprocessing
import numpy as np
import math
import pylsl
import pyqtgraph as pg
from pyqtgraph.Qt import QtCore, QtGui
from typing import List
# Basic parameters for the plotting window
plot_duration = 10 # how many seconds of data to show
update_interval = 30 # ms between screen updates
pull_interval = 50 # ms between each pull operation
class Inlet:
"""Base class to represent a plottable inlet"""
def __init__(self, info: pylsl.StreamInfo):
# create an inlet and connect it to the outlet we found earlier.
# max_buflen is set so data older the plot_duration is discarded
# automatically and we only pull data new enough to show it
# Also, perform online clock synchronization so all streams are in the
# same time domain as the local lsl_clock()
# (see
# and dejitter timestamps
self.inlet = pylsl.StreamInlet(info, max_buflen=plot_duration,
processing_flags=pylsl.proc_clocksync | pylsl.proc_dejitter)
# store the name and channel count =
self.channel_count = info.channel_count()
def pull_and_plot(self, plot_time: float, plt: pg.PlotItem):
"""Pull data from the inlet and add it to the plot.
:param plot_time: lowest timestamp that's still visible in the plot
:param plt: the plot the data should be shown on
# We don't know what to do with a generic inlet, so we skip it.
class DataInlet(Inlet):
"""A DataInlet represents an inlet with continuous, multi-channel data that
should be plotted as multiple lines."""
dtypes = [[], np.float32, np.float64, None, np.int32, np.int16, np.int8, np.int64]
def __init__(self, info: pylsl.StreamInfo, gl: pg.GraphicsLayout, plts: [pg.PlotItem]):
# calculate the size for our buffer, i.e. two times the displayed data
bufsize = (2 * math.ceil(info.nominal_srate() * plot_duration), info.channel_count())
self.buffer = np.empty(bufsize, dtype=self.dtypes[info.channel_format()])
empty = np.array([])
# create one curve object for each channel/line that will handle displaying the data
self.curves = [pg.PlotCurveItem(x=empty, y=empty, autoDownsample=True) for _ in range(self.channel_count)]
ch_ix = 0
for curve in self.curves:
plts[-1].setLabel('top', + ' channel ' + str(ch_ix))
ch_ix = ch_ix + 1
def pull_and_plot(self, plot_time):
# pull the data
_, ts = self.inlet.pull_chunk(timeout=0.0,
# ts will be empty if no samples were pulled, a list of timestamps otherwise
if ts:
ts = np.asarray(ts)
y = self.buffer[0:ts.size, :]
this_x = None
old_offset = 0
new_offset = 0
for ch_ix in range(self.channel_count):
# we don't pull an entire screen's worth of data, so we have to
# trim the old data and append the new data to it
old_x, old_y = self.curves[ch_ix].getData()
# the timestamps are identical for all channels, so we need to do
# this calculation only once
if ch_ix == 0:
# find the index of the first sample that's still visible,
# i.e. newer than the left border of the plot
old_offset = old_x.searchsorted(plot_time)
# same for the new data, in case we pulled more data than
# can be shown at once
new_offset = ts.searchsorted(plot_time)
# append new timestamps to the trimmed old timestamps
this_x = np.hstack((old_x[old_offset:], ts[new_offset:]))
# append new data to the trimmed old data
this_y = np.hstack((old_y[old_offset:], y[new_offset:, ch_ix] - ch_ix))
# replace the old data
self.curves[ch_ix].setData(this_x, this_y)
class MarkerInlet(Inlet):
"""A MarkerInlet shows events that happen sporadically as vertical lines"""
def __init__(self, info: pylsl.StreamInfo):
def pull_and_plot(self, plot_time, plts):
# TODO: purge old markers
strings, timestamps = self.inlet.pull_chunk(0)
if timestamps:
for string, ts in zip(strings, timestamps):
plts[0].addItem(pg.InfiniteLine(ts, angle=90, movable=False, label=string[0]))
def main():
# Create the pyqtgraph window
app = QtGui.QApplication([])
view = pg.GraphicsView()
gl = pg.GraphicsLayout()
plts: List[pg.PlotItem] = []
plts[-1].setLabel('top', text='All Inlets Marker Data')
# firstly resolve all streams that could be shown
inlets: List[Inlet] = []
print("looking for streams")
streams = pylsl.resolve_streams()
# iterate over found streams, creating specialized inlet objects that will
# handle plotting the data
for info in streams:
if info.type() == 'Markers':
if info.nominal_srate() != pylsl.IRREGULAR_RATE \
or info.channel_format() != pylsl.cf_string:
print('Invalid marker stream ' +
print('Adding marker inlet: ' +
elif info.nominal_srate() != pylsl.IRREGULAR_RATE \
and info.channel_format() != pylsl.cf_string:
print('Adding data inlet: ' +
inlets.append(DataInlet(info, gl, plts))
print('Don\'t know what to do with stream ' +
def scroll():
"""Move the view so the data appears to scroll"""
# We show data only up to a timepoint shortly before the current time
# so new data doesn't suddenly appear in the middle of the plot
fudge_factor = pull_interval * .002
plot_time = pylsl.local_clock()
plts[0].setXRange(plot_time - plot_duration + fudge_factor, plot_time - fudge_factor)
def update():
# Read data from the inlet. Use a timeout of 0.0 so we don't block GUI interaction.
mintime = pylsl.local_clock() - plot_duration
# call pull_and_plot for each inlet.
# Special handling of inlet types (markers, continuous data) is done in
# the different inlet classes.
for inlet in inlets:
# create a timer that will move the view every update_interval ms
update_timer = QtCore.QTimer()
# create a timer that will pull and add new data occasionally
pull_timer = QtCore.QTimer()
import sys
# Start Qt event loop unless running in interactive mode or using pyside.
if (sys.flags.interactive != 1) or not hasattr(QtCore, 'PYQT_VERSION'):
if __name__ == '__main__':
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