A simple API to estimate heart rate using PPG analysis data from mobile camera.
- 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.
- 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 cv2and 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 filterandhighpass filteris 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.SIGNALlibrary and average time between peaks were calculated. - Thus, calculating Heart rate.
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.
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
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
}