This is an old revision of the document!
Table of Contents
Moving RMS
The Moving_RMS command computes the linear envelope of a signal (typically an EMG signal) by calculating the RMS value within a moving window. The RMS is described here
The number of frames in the window must be an odd number. The output value at each frame is the RMS of the window centered on that frame.
Pipeline Command
The GCVSPL command can be found in the Pipeline Workshop within the Signal Filter folder as so:
Moving_RMS ! /Signal_Types= ! /Signal_Folder=ORIGINAL ! /Signal_Names= ! /RESULT_TYPES= ! /RESULT_FOLDERS=PROCESSED ! /RESULT_NAME= ! /APPLY_AS_SUFFIX_TO_SIGNAL_NAME= ! /NUM_WINDOW_FRAMES=3 ! /IF_EVEN_FRAMES_INCREMENT_1=FALSE ;
Command Parameters
The parameters that can be modified for this command are as follows:
| Signal Types | The type of signal to be processed |
| Signal Folder | The name of the origin signal folder |
| Signal Names | The names of the signals to be processed |
| Signal Components | Which components of the signal to be filtered |
| Result Types | The signal type of the resulting signals |
| Result Folder | The data tree folder in which the resulting signal is placed |
| Result Name | The name of the resulting signal that is produced |
| Apply As Suffix To Signal Name | True or False: Apply Result Name as a suffix to the original signal name |
| Num Window Frames | Number of frames included in moving window |
| If Even Frames Increment 1 | True or False: If frame window is an even number add 1 to make it odd and centered around middle frame |
Dialog
The command can be defined by editing as text using the parameter definitions above, or using the dialog box:
Frame Window
The command Moving_RMS computes the RMS of a signal by calculating the RMS value for short successive time periods (the time period is described as a moving window). In Visual3D the windows overlap. The output value at each frame is the RMS of the window centered on that frame (e.g. the RMS value for each window is plotted at the time corresponding to its center) so the number of frames in the window must be an odd number.
So, if the window was 11 frames.
- The first output frame is frame 6 computed from frames 1-11.
- The second output frame is frame 7 computed from frames 2-12 Etc.
Typically, this window is reported as a time. Since the number of frames is dependent on the sampling rate, you must convert the time (in seconds) to frames. The sampling rate is specified in the C3D file under PARAMETER::ANALOG::RATE.
To convert time to frames, you must multiply the time by the sampling rate and add 1 (time 0.0 is equal to frame 1). This as an expression is:
( time * PARAMETER::ANALOG::RATE ) + 1
To specify a frame window of 100 ms (0.1 seconds), would be specified as:
/NUM_WINDOW_FRAMES=( 0.1 * PARAMETER::ANALOG::RATE ) + 1
Example: Pipeline commands for specifying a window of 100 ms
A more typical window for the RMS filter is 100 ms, which can be achieved as follows:
! -------------------------------------------- ! compute a moving rms with a window of 100 ms ! -------------------------------------------- Moving_RMS /SIGNAL_TYPES=ANALOG /SIGNAL_FOLDER=ORIGINAL /SIGNAL_NAMES=EMG1+EMG2 /RESULT_TYPES=ANALOG /RESULT_FOLDERS=RMS /RESULT_NAME= /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=TRUE /NUM_WINDOW_FRAMES=(0.1*PARAMETER::ANALOG::RATE)+1 ! /IF_EVEN_FRAMES_INCREMENT_1=FALSE ;
Example: Pipeline commands for specifying a window of 150 ms
To specify a 150 ms (0.15 seconds) window for the RMS, the commands are as follows:
! -------------------------------------------- ! compute a moving rms with a window of 150 ms ! -------------------------------------------- Moving_RMS /SIGNAL_TYPES=ANALOG /SIGNAL_FOLDER=ORIGINAL /SIGNAL_NAMES=EMG1+EMG2 /RESULT_TYPES=ANALOG /RESULT_FOLDERS=RMS /RESULT_NAME= /APPLY_AS_SUFFIX_TO_SIGNAL_NAME=TRUE /NUM_WINDOW_FRAMES=(0.15*PARAMETER::ANALOG::RATE)+1 ! /IF_EVEN_FRAMES_INCREMENT_1=FALSE ;