Heart Rate API

A simple API to estimate heart rate using PPG analysis data from mobile camera.

Use

• Record a 15 second video by keeping finger over the camera with flash on.
• Send url link of video to the api to perform PPG and estimate heart rate.

Approach

• Place finger over the camera and 15 second video was recorded with flash on in each case.
• This video is imported to our python based api using open cv2 and video object was created, FPS, frame count were determined.
• The first few frames and last few frames were dropped as a data pre processing measure as they contain most of the error. eg. placing finger and removing finger, stablizing time etc.
• For each image of the video, pixels in the middle were selected and average of RGB colors were calculated.
• Array of each RGB color was maintained to storage average values.
• Array with red pixels was selected for further processing and determination of results as red color gives best result (Assumption)
• Following arrays were treated as signal objects.
• Lowpass filter and highpass filter is use to remove unwanted frequencies from signals.
• Further, signal was squared to elongate it, so that it was easy to determine peaks (Assumption)
• Peaks were detected using peak detection algorithm from SCIPY.SIGNAL library and average time between peaks were calculated.
• Thus, calculating Heart rate.

Deployed API link

https://heart-rate-07.herokuapp.com/api?query=video_url_link

The query must contain url link of ppg data captured using mobile camera with flash on.

Example of API call

https://heart-rate-07.herokuapp.com/api?query=https://firebasestorage.googleapis.com/v0/b/heart-rate-monitor-cee6e.appspot.com/o/files%2Ftest.mp4?alt=media&token=61d6c17c-4f85-4c32-b9a7-7ea0fd19400c

Example of API response

API response example

{
   "r_avg":[
      0.00018912736029968232,
      0.002454027341541433,
      0.0046238379461607014,
      0.0059273051392782815,
      .....
   ],
   "g_avg":[
      5.739757749447178e-05,
      0.002728729471758443,
      0.005252370906011639,
      0.006246822018310483,
      .....
   ],
   "b_avg":[
      0.00012713453865537887,
      0.0009398674441625056,
      0.001593039182660829,
      0.0019041612619612055,
      .....
   ],
   "r_bpm":131.9763664543775,
   "g_bpm":112.5044435348792,
   "b_bpm":104.61541243334804,
   "avg_bpm":116.3654074742016
}

References

• Scipy Signal
• Research Gate
• Open CV
• heart rate ppg camera