Video Input Requirements

to ensure a reliable assessment of health parameters from video, the recording must meet specific input requirements as a commitment to maintaining a quality first approach, we refrain from delivering results when accuracy cannot be guaranteed due to unmet input requirements in such cases, the face scan plug in provides clear guidance on how to improve conditions or perform the measurement correctly if requirements still cannot be met due to factors outside the user’s control – such as slow internet or poor lighting – the plug in will notify your platform, allowing you to handle the situation gracefully subject and environment subject stillness and position it is important for the subject to remain still during the recording and center the face within the recording frame the goal is to keep looking at the camera and minimize head movement the setup is similar to when taking a portrait photo lighting it is important to perform the recording in a well lit room a lighting of at least 200 lux is recommended our face scan plug in automatically guides the user to a correct position and lighting prior to starting the scan for comprehensive guidelines on how to correctly sit in front of the camera during the measurement, refer to our usage instructions docid\ jud0qrczbbcutskbyezu0 recording frame rate the video frame rate should at least be 20 fps and should not exceed 60 fps the recommended value is a recording frame rate of 30 fps the face scan plug in automatically checks whether the framerate is sufficient and prompts the user if it's not resolution, codec and bitrate our face scan plug in automatically ensure these requirements are met 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 resolution between 320p and 1080p codec h264 or h265 if supported; vp8 when recording in most browsers bitrate depending on resolution and codec, see table below more info on why these parameters are important firstly, video resolution refers to the number of pixels contained in each frame of the video higher resolutions provide more detailed images, allowing for better visualization and analysis of subtle color variations in the skin when measuring the blood volume pulse, these color differences are crucial for accurately detecting changes in blood flow and accurately determining values like heart rate and heart rate variability therefore, we recommend a resolution between 320p and 1080p secondly, the choice of codec, which determines how the video is compressed and encoded, can have an impact on the fidelity of the captured data some video codecs employ heavy compression techniques that can introduce artifacts or loss of detail in the video it is important to select a codec that preserves color information and minimizes compression artifacts, as these artifacts can interfere with the accurate detection of subtle skin color changes codecs like h 264 or h 265 (hevc) are commonly used and provide good compression efficiency while maintaining reasonable video quality when working with mobile devices and recording the video in the browser , we recommend the vp8 codec, which typically allows achieving higher framerates than alternative codecs lastly, the video bitrate plays a crucial role in determining the amount of data allocated to each second of video footage higher bitrates allow for more data to be captured and preserved, resulting in better representation of subtle color changes in the skin insufficient bitrate allocation can lead to loss of fine details, making it challenging to accurately extract the blood volume pulse signal it is advisable to use higher bitrates when recording videos, especially if the intended application involves precise heart rate measurement below you find a reference table with the minimal bitrate values (expressed in kbps) to which videos must comply mind that the minimal bitrate is both depending on the resolution and video codec bitrate (kbps) h264 h265 320p 4700 4030 480p 1030 1280 640p 2320 1540 720p 1220 1940 1080p 850 2890 w e recommend using a tool like https //www metadata2go com https //www metadata2go com to verify your camera's performance the r frame rate field should contain a value between 30 and 60 fps camera camera sensor size & pixel size 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 these values are standard for most smart devices and laptops from the last 5 to 6 years for example, the front camera of the samsung galaxy s8 from 2017 meets these requirements lens quality 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 lenses of lower quality (e g plastic) may work, but this is not guaranteed, as these materials scratch up more easily and the optical quality varies greatly