EDFbrowser reads and shows trigger inputs.

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Teuniz
Posts: 37
Joined: Wed Feb 06, 2008 9:42 am
Location: Neverland

EDFbrowser reads and shows trigger inputs.

Post by Teuniz »

EDFbrowser now has support for Biosemi's "Status" signal in two ways:

When opening a "genuine" Biosemi data file in EDFbrowser, it will
show the Trigger Inputs in the annotationwindow.
Like normal annotations, it will also draw a vertical dashed white line
on the screen for every trigger. This behaviour can be switched off in
the settings menu. When you click on a trigger in the annotationwindow,
EDFbrowser will jump to that fileposition.


It is also possible to convert the Status signal into BDF+/EDF+ annotations
using the "Biosemi to BDF+ converter" in the Tools menu of EDFbrowser.
The advantage of this converter is that you can change the names of the different
Trigger Inputs to something like "Flash 20Hz", "Stimulus 2", etc.
You can also select rising or falling edge.
Another advantage of this converter is that the new file can be converted
to EDF+ while preserving your annotations (Trigger Inputs) using the
"BDF to EDF converter" in the Tools menu of EDFbrowser.

Some properties of the converter:

- It makes a copy of the original file. The original file will not be altered.

- It inserts a "BDF Annotations" signal into the new file which contains the
Biosemi trigger inputs and the "new epoch" bit extracted from the "Status" signal.

- The "Status" signal will be preserved in the new file.

The Biosemi to BDF+ converter can be found in the Tools menu.

The description of the annotations can be changed before starting the conversion.
By selecting "rising edge" or "falling edge", you instruct the converter to create
an annotation/event when detecting a transition from 0 to 1 or 1 to 0.
Bit 16 (new epoch) will always use rising edge.
Checking the "measure event duration" checkbox, instructs the converter to measure the
duration of an event, i.e. the time between the rising and falling edge (or the falling and
the rising edge, depending to the selection).
(An EDF+/BDF+ annotation can store three items: onset, duration and a description of the event.
Onset and description are obligatory, duration is optional.)

After opening the new/converted file in EDFbrowser, you will see all the trigger inputs
in the annotationwindow. You can jump to a specific trigger by clicking on the respective annotation.
Annotations can be exported, check the Tools menu in EDFbrowser.
Annotations can be added, edited or removed by using the annotation-editor,
check the Windows menu in EDFbrowser.

The new file can be converted to EDF+ while preserving your annotations.
Use the BDF to EDF converter in the Tools menu.

BDF+ is backwards compatibel with BDF and can be read and processed by older BDF software
(apart from the annotations ofcourse).


Limitations of the converter:

- The maximum number of annotations (Trigger Input events) in the new file
is: duration of file in seconds multiplied by 32 (but the total can never be
more than 100000).
If the original file contains more trigger input events, they will be ignored.
If, for example, the duration of a file is 5 minutes, the first 9600 trigger input
events will be converted to BDF+ annotations.

- The precision of the annotations is limited to 100 microSeconds (0.0001 sec.).

- Only the 17 lowest bits of the Status signal will be evaluated and converted
(the 16 trigger input bits plus the "new epoch" bit).


Let me know if you have any comments, found a bug or omission (or if you like this converter).

http://www.teuniz.net/edfbrowser/

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