Data Subscription

After you opened a session with a headset, you can subscribe to one or more data streams.

Each data steam gives you real time access to data from the headset (EEG, motion...) or data calculated by Cortex (band powers, mental command...)

After you successfully subscribe to a data stream, Cortex will keep sending you data sample objects.

A subscription is linked to a session. All the subscriptions of a session are automatically cancelled when the session is closed. You can call unsubscribe to cancel a subscription.

The available data streams depend on the license of the user, and the model and settings of the headset. For an EPOC Flex, it also depends on the EEG sensor mapping.

Data streams

Each data stream is identified by its name: "eeg", "mot", "dev", "eq", "pow", "met", "com", "fac", "sys".

Stream	Description
eeg	The raw EEG data from the headset.
mot	The motion data from the headset.
dev	The device data from the headset. It includes the battery level, the wireless signal strength, and the contact quality of each EEG sensor.
eq	The EEG quality of each EEG sensor. Please read this page to understand the difference between the contact quality and the EEG quality.
pow	The band power of each EEG sensor. It includes the alpha, low beta, high beta, gamma, and theta bands.
met	The results of the performance metrics detection.
com	The results of the mental commands detection. You must load a profile to get meaningful results.
fac	The results of the facial expressions detection.
sys	The system events. These events are related to the training of the mental commands and facial expressions. See BCI for details.

Data streams availability

Depending on the license and the model of the headset, some streams may be available or not, and may send data samples objects at a different rate.

Stream	Supported headsets	Sample rate in hertz
eeg	All, but requires a license	128 or 256, depends on the headset and its settings. The license must contain the scope "eeg". You must activate the session before you subscribe. Please check the documentation of your headset.
mot	All	Disabled, 32, 64, 128, depends on the headset and its settings. 6.4 hertz for MN8. Please check the documentation of your headset.
dev	All	2
eq	All	2
pow	All	8
met	All EPOC Flex requires a special EEG sensor mapping	2 if the license contains the scope "pm" and you activate the session before you subscribe. 0.1 otherwise (1 sample every 10 seconds)
com	All EPOC Flex requires a special EEG sensor mapping	8
fac	All but MN8 EPOC Flex requires a special EEG sensor mapping	32
sys	All	No fixed rate, see BCI for details.

Special EEG sensor mapping for EPOC Flex

By default, the streams "met", "com" and "fac" are not available for EPOC Flex. It is because Cortex doesn't implement the detections (performance metrics, mental command, facial expression) for EPOC Flex.

However, you can configure your EPOC Flex to simulate an EPOC X headset. In that case, Cortex runs the detections that are designed for EPOC X.

All you have to do is to use a sensor mapping that includes all the 14 EEG sensors of an EPOC X headset: AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6, F4, F8, AF4. In addition, you should use P3 and P4 as references CMS and DRL. Please see the EPOC X user manual for the complete EPOC X configuration.

Your mapping can also include sensors that are not present on an EPOC X. Cortex will not use these additional sensors to run the detections, but you can use them to collect more EEG data.

You must configure the EEG sensor mapping of your EPOC Flex when you call the method controlDevice.

This feature was added in Cortex 2.7.1