To allow for a qualitative measurement of the biometric parameters from a video, we ask to meet the guidelines below. Parameters marked with 'required' must be met. Parameters marked with 'optional' are recommended, but not obligated.
The camera sensor is the part of the imaging system that is sensitive to light. The size of this sensor plays an important role in the final quality of the image or video. The larger the sensor, the more sensitive it is to light. Larger image sensors have larger pixels, which means less noise, better dynamic range and the ability to obtain more (subtle) information. The size of the sensor should be at least 5.0 mm in diagonal. The size of a pixel (unit cell) should be at least 1.0 μm.
Lens quality is becoming more important with the increasing pixel count on modern cameras. The resolution of digital photos is often limited by the camera lens rather than the resolution of the camera itself. In order to perform a qualitative measurement, the lens should have an aperture of at least f2.8 and be made from glass or an (optically) higher quality material.
The recording length of the video should be at least 20 seconds and should not exceed a length of one minute. A video length of 30 seconds is recommended.
A video length of 30 seconds provides a nice trade-off between accuracy, processing time and user experience.
Video's with a duration less then 20 seconds will not be processed. More info can be found here: API docs > Get results > video too short.
The video frame rate should at least be 30 fps and should not exceed 60 fps. The recommended value is a recording frame rate of 30 fps.
Higher frame rates may lead to a marginal increase in accuracy, but highly increases upload and processing time.
In case you are not sure the video is recorded correctly, we recommend using a tool like https://www.metadata2go.com to verify the video's metadata. The r_frame_rate field should contain a value between 30 and 60 fps.
The video resolution, codec, and bitrate are critical properties to consider when capturing and processing video data for measuring the biomarkers using our algorithm. These factors play a vital role in preserving the necessary information about the blood volume pulse, which is essential for accurate measurements.
More info on why these parameters are important
Below you find a reference table with the minimal bitrate values (expressed in kbps) to which the videos must comply. Mind that the minimal bitrate is both depending on the resolution and video codec.