Knowledge Base

Manual Synchronization

Aim

To synchronize the external dataset manually with the event log and the videos.

Prerequisites

• Your license for The Observer XT includes the External Data Module.
• You did not use automatic synchronization with a synchronization signal to acquire your external data. See Set Up Your Experiment with Synchronization Signal.

Procedure

There are three methods for manual synchronization:

• Numerical offset – If you know how many seconds the observational and external data are out of sync.
• Manual offset – For visual synchronization. Use this method when you score from a media file and the start of the observation or external data acquisition is signaled by a visual or auditory cue. For example, you counted down until you pressed the Start button in the DAQ system and you can hear this on the recorded video. See also Set Up Your Experiment with Stand-Alone External Data Acquisition.
• Change the start or stop time with manual import.

Numerical Offset

1. Open the observation in which you imported the external data.
2. On the component toolbar, click the Offset button.
3. Select Numerical Offset to open the File Synchronization window.
4. Synchronize the files by entering the offset values. For example, if you started your observation 3 seconds before you started acquisition of external heart rate data, enter 3.00 for the heart rate. The external data stream now starts 3 seconds after the event log.

Manual Offset

1. Open the observation in which you imported the external data. The current position in the event log is highlighted in blue and a red vertical line in the External Data window indicates the current position.
2. Click the Offset button on the toolbar and choose Manual offset. A window appears with instructions on how to set the offset in a video, audio file, or external data window.
3. Click Start Synchronization.
4. Click the External Data window; the border of this window turns red and the cursor becomes an offset icon.
5. Keep the left mouse button pressed to drag the graph window to the left or the right to the point where the external data match the event or the video frame.
6. Click the Offset button on the toolbar once more to finish synchronization.

Change the Start or Stop Time with Manual Import

When you import external data and choose Manual import (see To Import a Specific Data Set), a window with data sets appears together with the Independent Variables list. In the window with data sets, edit the Start time or Stop time cell. By changing the start time you set the offset of a file. By changing the end time and/or start time you set the gain by stretching or shrinking your file.

Import External Data, Special Cases

What do you want to do?

• Create an Import Profile
• Import External Data Files with Missing Samples
• Import Heartbeat Intervals

Create an Import Profile

Aim

To import external data as text files when The Observer XT does not have a predefined import profile (see step 2 in Import External Data as Text Files). With an import profile you create a template based on the structure of the external data file.

Prerequisites

• Your license for The Observer XT includes the External Data Module.
• You exported your external data as text files.

Procedure

1. Choose File > Import > External Data.
2. Click the Custom Import Profiles button and then the New button.
3. Browse to the external data file.
4. Build the import profile by specifying the structure of the data file. This is done by dragging and dropping cells. To undo a selection, select the cell to which content was dropped and press Delete. Follow the procedure in these sections:
   1. Header
   2. Delimiters
   3. Time Information
   4. Data
5. Import a text file with the new import profile.

1 - Header

The Observer XT usually automatically detects header and data information in the file. If not, specify which part of the data file contains the header. Choose an option from the Header detection list:

• Automatic (default) – The Observer XT is set to automatically detect the header and data sections in the data file. Choose one of the other options if automatic header detection does not work.
• Specify tag – Select this option if the data file has a variable number of header lines and the header always ends with the same word. Specify the phrase (with either nominal or numerical information) that indicates the end of the header part of the file. If necessary, also specify the number of rows between the header line that contains this phrase and the data. For example, if the header always ends with a line containing the text [Data] and after that line there is always an empty line before the data starts, enter [Data] in the End tag field and 1 in the Extra rows field.
• Specify row number – If the data file always has the same number of rows in the header, select this option and specify the number of header rows.

2 - Delimiters

The Observer XT uses the comma as the default delimiter to separate text in the header and data sets. However, the data file may have other delimiters. If this is the case, select the correct ones from the Select header delimiters and Select data delimiters lists. You can also select multiple delimiters. Some DAQ software enables you to select the type of delimiter when saving the DAQ data to an ASCII export file. In that case, select the same delimiter in the File content section of the Profile Definition window. A comma or semicolon are advised as delimiters.

3 - Time Information

Specify which cell or column contains the time information. This can be a column with time stamps, a cell with the sample rate, or a cell with the sample interval, which is the time between samples. Drag and drop the cell or column with time information to the appropriate field in the Profile definition section.

1. Sample rate – If the header contains a cell with the sample rate, select the Sample rate button under Timing based on in the Profile definition section.