Scan Conditions

The ScanConditions object returned by the Vitals™ SDK through the onVideoFrameProcessed callback function comprises of the following 6 conditions:

Scan ConditionScan Condition	DescriptionDescription
Centered	Whether the user's face is centered in the camera frame.
Distance	Whether the distance between the user's face and the camera is suitable.
Lighting	Whether the lighting is sufficient.
Movement	Whether the face is stable.
Frame Rate	Whether the frame rate is high enough.
Server Ready	Whether the server is ready.

Most of these conditions will only be checked when the user's face is detected within the frame. If no face is detected, these conditions will not pass and return false.

Face Detected

In line with the Best Practices for Vitals™ Health Assessment, the user should place the camera at eye level and ensure the face is fully visible and not covered (e.g., with a mask, hoodie, or hair). These are to ensure that face could be successfully detected, and the blood flow information in the regions of interest (ROIs) could be extracted for conducting Vitals™ measurements.

TIP

When face is not detected, most of the scan conditions will not pass. You do not need to explicitly check this in your code, but you could choose to use the NormalizedFacebox object to perform any actions needed for your use cases, e.g., display a face bounding box.

Centered

As described in Best Practices for Vitals™ Health Assessment, users should place the camera at eye level, ensuring the entire face and upper chest are captured within the camera frame. Vitals™ verifies if the user is positioned centrally within the camera frame to fulfill this requirement effectively.

TIP

For optimal results, it is recommended to conduct the Vitals™ scan with the X Center of the user's face falls within 40% - 60% of the camera frame's width, while the Y Center is between 30% - 70% of the camera frame's height.

Distance

As outlined in Best Practices for Vitals™ Health Assessment, users should ensure their entire face and upper chest are captured. This could be done by maintaining a suitable distance with the camera. This ensures that the user is far enough for the camera to capture the entire face and the upper chest, and also close enough for the signals to be observed.

TIP

For optimal results, it is recommended to conduct the Vitals™ scan with a distance of 0.4 meters to 0.6 meters between the user's face and the camera. That is, the height of the user's face box should be roughly 30% - 50% of the camera frame's height.

Lighting

In line with the Best Practices for Vitals™ Health Assessment outlined, it is crucial to ensure that the user's face is clearly visible with even and consistent lighting. It is advisable to avoid uneven lighting conditions such as direct sunlight or backlighting, and opt for a well-lit environment with uniform illumination.

TIP

For optimal results, it is recommended to conduct the Vitals™ scan indoors with an illuminance of 300 lux or higher.

Movement

Described in the Best Practices for Vitals™ Health Assessment, users should avoid making significant movements during the scan, such as moving their body, shaking or significantly tilting their device. Vitals™ monitors the most recent 30 frames processed to check if the face deviates significantly within this window.

TIP

For optimal results, it is recommended to avoid any movement during the Vitals™ scan and remain the entire face and body stable. The user can and should, however, blink and breathe as usual during this process.

Frame Rate

Frame rate affects how much signals could be extracted from the 30-second Vitals™ scan. It is therefore crucial to ensure the device supports a high enough frame rate for obtaining medical-grade measurement results.

TIP

For optimal results, it is recommended to maintain an average frame rate of at least 15 frames per second (fps) during the Vitals™ scan. If the frame rate condition cannot pass, please try to use another device to conduct Vitals™ Health Assessment.

Server Ready

The Vitals™ Cloud Service, i.e. the cloud server, is hosted in Amazon Web Services (AWS) for performing data analysis and returning the vital sign results back to the Vitals™ SDK. To ensure the server is ready and avoid users requiring to wait for the server cold boot time, Vitals™ SDK monitors if server is alive.

TIP

To ensure HTTPS requests could be successfully sent to the Vitals™ Cloud Service for vital sign measurements, it is recommended to maintain a good network conditions throughout the Vitals™ scan process.