Signal Analyzer Element

Summary ¶

	Signal Analyzer
Info
Category:	Signal Processing		AddIn:	Signal Processing
Creator:	OkazoLab		Scope:	Parent event
Owns Snippets:	None		Usage:	Snippets

Properties ¶

Name	Description	Constraints	Type	On runtime change
Signal Source
Selected Signal	Defines the signal for processing by the element. The signals are provided by the data acquisition elements.	Design Time..	Int32
Sampling Rate	Defines the sampling rate of the original signal, in Hz	Design Time..	Double
Analysis Window Size	Defines the size (in samples) of the moving analysis window for signal processing.	Design Time..	Int32
Signal Normalization	Defines the normalization procedure that is automatically applied to the signal before the analysis	Normal..	enSign..
Bandpass Filter
Is Filtering	Defines whether the Butterworth bandpass filter is applied in signal plotting. This filter does not affect the signal analysis.	Normal..	Boolean
Filter Order	Defines the order of the Butterworth bandpass filter	Normal..	Int32
Low CutOff	Defines the low cutoff of the Butterworth bandpass filter, in Hz	Normal..	Double
High CutOff	Defines the high cut-off of the Butterworth bandpass filter, in Hz	Normal..	Double
Runtime Status
Is Running	Defines whether the analysis and plotting is going on in the present. You can use this property to temporally cease the signal processing for a sake of performance.	Normal..	Boolean
XAML Signal Plot	Returns a live XAML signal plot with the signal data. The plot can be used for direct binding to the Content property of the XAML ContentControl element, e.g. The ContentControl with a generated plot can be shown on the status screen or by the XAML Layout element.	Normal..	UIElem..
All Samples	Returns all samples in the analysis window as a double array. The array length is equal to the size of the analysis window. The values are updated every Control Loop cycle of the parent event. The last item in the array corresponds to the most recent signal sample.	Normal..	Double..
New Samples Count	Returns a number of new samples that were recorded during the last Control Loop cycle	Normal..	Int32
Newest Sample	Returns the most recent sample in the analysis window as a double value. The value is updated every Control Loop cycle of the parent event, given that new signal data is recorded.	Normal..	Double
Newest Samples	Returns an double array of the newest samples, which were recorded during the last Control Loop cycle. The array is a rightmost segment of the analysis window	Normal..	Double..
Add Marker Now	Assign 'true' in snippets at runtime, in order to add a synchronized marker (vertical line) at the zero-time point on the signal plot.	Runtime Command..	Boolean
Plotting
Plot Title	Defines the title of the generated signal plot	Normal..	String
Plot Theme	Defines a visual theme of the generated signal plot	Normal..	Int32
Line Thickness	Defines the thickness of the data line on the generated signal plot	Normal..	Int32
Line Color	Defines the color of the data line on the generated signal plot	Normal..	stColor
Font Size	Defines the font size for plot labels	Normal..	Double
Show Axis Bands	Defines whether the axis bands are shown on the plot area	Normal..	Boolean
Rendering Size	Defines the size of the generated plot in pixels. The plot is automatically stretched on rendering, but a larger rendering size improves the chart quality with some cost in performance. The rendering size is also used as the resulting image resolution, when the plot is exported into a file.	Design Time..	clSize
Sync Marker Color	Defines a color of the custom synchronization markers	Normal..	stColor
Sync Marker Width	Defines the width of the custom synchronization markers on the X axis	Normal..	Double
Show Threshold Slider		Normal..	Boolean
Threshold Value		Normal..	Double
Signal Statistics
Mean	Returns the means of the signal values within the analysis window	Normal..	Double
Minimum	Returns the minimum of the signal values within the analysis window	Normal..	Double
Maximum	Returns the maximum of the signal values within the analysis window	Normal..	Double
Standard Deviation	Returns the standard deviations of the signal values within the analysis window	Normal..	Double
Control
Is Enabled	If set to false the element is completely omitted when the experiment is run	Design Time..	Boolean
Title	Title of the element	Design Time..	String

¶

Description ¶

Snapshots ¶

The status screen showing the signal plot, statistics and the recent signal samples

Practical Use ¶

Preparing the element ¶

1. Make sure that your experiment contains one of the data acquisition elements, e.g. OpenViBE Signal element
2. Prepare the data acquisition element such that it is set to collect at least one signal channel.
3. Add new Signal Analyzer element to the event, where you plan to process the signal (the element operates only within the parent event).
4. Select the added element to browse its properties in the Property panel.
5. Define a signal for processing, via the Selected Signal property.
6. Adjust the Sampling Rate property such that the value matches to a real sampling rate of the selected signal.
7. Choose the size of the analysis window via the corresponding property.
8. Select the Signal Normalization procedure, if required.
9. If you want to filter the signal for plotting, turn on the bandpass filtering in the Bandpass Filter group and adjust the filter parameters.
   

Creating the signal plot ¶

1. Create a proxy variable linked to the XAML Signal Plot property
2. Check the visual plot settings in the Plot Settings group
3. Add a XAML content control with data binding to the Status Screen code:
   

   
   
   <ContentControl Content='{Binding XAMLSignalPlot}'/>
   
   

   
   

Accessing the descriptive statistics of the signal samples ¶

1. Create proxy variables linked to the Mean,Maximum,Minimum and Standard Deviation properties of the element
2. If you want to access the statistics in code, use the Control Loop snippet of the parent event to monitor all signal updates:
   

   
   
   // Merging the statistics values into a string
   
   string Statistics="Mean="+Mean+"\n Maximum="+Maximum+" \n Minimum="+Minimum+" \n SD="+StandardDeviation;
   
   

3. If you want to monitor statistics on the status screen at runtime, you can use the XAML textblocks bound to the proxy variables:
   

   
   
   <TextBlock Text='{Binding Mean,StringFormat=Signal Mean: {0:F2}}' Foreground='Orange' FontFamily='Calibri' FontSize='16'/>
   
   

   
   

Reading the signal samples in code ¶

1. Create a proxy variable linked to the Signal Samples property
2. Use the Control Loop snippet of the parent event to monitor all signal updates
3. Create a loop to read all signal samples:
   

   
   
   // estimate the sum of the signal samples within the analysis window
   
   double Sum=0;
   
   for (int i=0;i,SignalSamples.Length;i++)
   
   {
   
   Sum=Sum+SignalSamples[i];
   
   }
   
   

   
   

Notes ¶

• Although the size of the analysis window is defined in samples, the signal plot draws the signal over a time taking in the account the sampling rate.
• The bandpass filtering affects only signal plotting, not the signal analysis.
• You can measure a time of one cycle of signal processing with the Control Loop Interval property on the parent event. With plotting on and off, the expected time is ~10 and ~5 ms, correspondingly, given that there are no other processes in the parent event and in the experiment.
• If you are in time-critical section of your experiment, you can temporally cease the signal processing by setting the Is Running property to false.