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.

Data streams

Each data stream is identified by its name: "eeg", "mot", "dev", "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.

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.

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 contains the scope "eeg". You must activate the session before you subscribe.

mot

All

Disabled, 32, 64, 128, depends on the headset and its settings.

dev

All

Same as the "eeg" stream.

pow

All

8

met

All but EPOC Flex

2 if the license contains the scope "pm" and you activate the session before you subscribe. 0.1 otherwise.

com

All but EPOC Flex

8

fac

All but EPOC Flex

32

sys

All

No fixed rate, see BCI for details.