RECORDA is an Android application to record LabStreamingLayer (LSL) streams directly on a smartphone. Much like the LabRecorder, RECORDA detects LSL streams on the network and records them in the standard file format for LSL streams (XDF, "Extensible Data Format").
In our lab, RECORDA is mainly used in combination with SENDA, an Android app which streams data from all available sensors on the phone. Typically, the built-in sensors include:
- Accelerometer
- Light
- Proximity
- Gravity
- Linear Acceleration
- Rotation Vector
- Step Count
For a complete list and full specifications on the sensor data, please check out the official Android Sensor Documentary.
However, since RECORDA is using the LSL framework, it can record any kind of LSL stream, they can stem from separate devices on the same network.
Download the latest release and install the apk on your smartphone or tablet running Android 8.0 or higher.
After the start of the application, the user is presented with the home screen, containing all main UI elements. The user can refresh the list of available network streams by clicking the refresh button at the top right. All available streams are then listed in the list view below in the format Stream Name (Sampling Rate). The desired streams should be selected from this list before starting the recording. Recording is initiated by pressing the Start button. Once the experiment is complete, the user should press the Stop button and wait while the file is finalized. The application will display a notification when the file is ready, including the file’s location on the device. The gear button on the top left opens a settings dialog. An optional recording name can be configured in the settings; if no name is provided, a unique name will be automatically generated for each new file.
During a recording, RECORDA monitors the quality of the selected streams. The quality can have three different states: good, laggy, or bad. Good streams are not highlighted in the UI with a specific color, whereas laggy streams will have a yellow background and bad streams will have a red background. If a good stream changes to laggy or bad, a heads-up notification is shown to the user, even if RECORDA runs in the background.
There are several checks that can lead to a change in quality:
- If the LSL method
pull_samplesreturns an error, the quality of the respective stream is set to bad. RECORDA will continue to callpull_samples, and if new samples are successfully received, the quality will switch back to good. This behaviour is implemented for regular, as well as irregular streams.
Additionally, for streams with a nominal regular sampling rate, two checks are being performed:
- The duration in which we did not receive any samples (timeout value for laggy: 1.5 seconds, timeout value for bad: 7 seconds)
- A comparison of the nominal sampling rate with the actual detected sampling rate in a recent time window (of 10s by default). If a lower sampling rate is being detected, the stream is considered laggy (threshold default value 90%). This metric never causes the bad state.
The worse result of these two metrics will be displayed in the UI.
Importantly, streams being declared as having an irregular nominal sampling rate by the sending side, are not checked with the timeout or deviating sampling rate checks.
Once data has been recorded, transfer the file to your computer and then open the file with a program of your choice. For Matlab, there are multiple XDF readers available, for example this one.
We suggest to download and install the latest release of the app as described above. However, if you want to build the app yourself, you can also clone this repository and then open the project with Android Studio.
- Android Studio Giraffe | 2022.3.1 Patch 2
- Android API 34 SDK platform
- Android NDK 25.2.9519653
- CMake 3.22.1
RECORDA is developed using the versions listed above. Other versions may or may not work and are not tested.
Please feel free to contribute to this project by creating an issue first and then sending a pull request against the issue.
The app is actively developed by the neuropsychology group of Stefan Debener in Oldenburg, Germany.
Ali Ayub Khan - AliAyub007
This project is licensed under GNU General Public License - see the LICENSE.md file for details
liblsl, used under MIT license liblsl-Java, used under MIT license libxdf adapted from App-LabRecorder code, used under MIT license
- Blum S, Hölle D, Bleichner MG, Debener S. Pocketable Labs for Everyone: Synchronized Multi-Sensor Data Streaming and Recording on Smartphones with the Lab Streaming Layer. Sensors. 2021; 21(23):8135. https://doi.org/10.3390/s21238135