diff --git a/ppg.cpp b/ppg.cpp
index 9af031b..668ab82 100644
--- a/ppg.cpp
+++ b/ppg.cpp
@@ -3,18 +3,21 @@
 #include "opencv2/videoio.hpp"
 #include "opencv2/highgui.hpp"
 
+
+#define BUFFER_DURATION 30.0
 #define FPS 30.0
 #define temps 1.0
 
 bool isDiscardData = true;
 int countDiscard = 0;
+bool isBufferFull = false;
+int sampleIdBuffer = 0;
 
 int main() {
     std::cout << "PPG, j'adore gitbash même si avec github desktop c'est mieux" << std::endl;
 
     cv::VideoCapture cap;
     cap.open(0);
-
     cv::CascadeClassifier faceDetector;
     if (!faceDetector.load("./haarcascade_frontalface_alt.xml")) {
         std::cerr << "[ERROR] Unable to load face cascade" << std::endl;
@@ -48,13 +51,25 @@ int main() {
             cv::cvtColor(frame, frame_gray, cv::COLOR_BGR2GRAY);
             std::vector<cv::Rect> faceRectangles;
             faceDetector.detectMultiScale(frame_gray, faceRectangles, 1.1, 3, 0, cv::Size(20, 20)); 
-            for (size_t i = 0; i < faceRectangles.size(); i++) {
-                cv::rectangle(frame, faceRectangles[i], cv::Scalar(255, 0, 0), 2);
-                cv::Rect foreheadROI = faceRectangles[i];
-                foreheadROI.height *= 0.3;
-                cv::rectangle(frame, foreheadROI, cv::Scalar(0, 255, 0), 2);
-            }
+            cv::rectangle(frame, faceRectangles[0], cv::Scalar(255, 0, 0), 2);
+            cv::Rect foreheadROI = faceRectangles[0];
+            foreheadROI.height *= 0.3;
+            cv::rectangle(frame, foreheadROI, cv::Scalar(0, 255, 0), 2);
             cv::imshow("Color", frame);
+            cv::Mat frame_forehead = frame(foreheadROI);
+            cv::Scalar avg_forehead = mean(frame_forehead);
+            cv::Mat greenSignal(1, FPS*BUFFER_DURATION, CV_64F);
+
+         
+            if (!isBufferFull)
+            {
+            	greenSignal.at<double>(0, sampleIdBuffer) = avg_forehead[1] ;
+            	sampleIdBuffer++;
+            	if (sampleIdBuffer == FPS*BUFFER_DURATION)
+            	{
+            	isBufferFull = true;
+            	}
+            }
         }
 
         if (cv::waitKey(1000.0/FPS) >= 0) {