diff --git a/src/analyzer/framecache.py b/src/analyzer/framecache.py
--- a/src/analyzer/framecache.py
+++ b/src/analyzer/framecache.py
@@ -4,9 +4,21 @@ from collections import deque
 class FrameCache:
 	def __init__(self,capacity=600): # 600 is enough for 10 min of 1 fps
 		self._capacity=capacity
-		self._cache=deque()
+		self._keys=deque()
+		self._values=dict()
+		self._i=0
 
-	def put(self,frame):
-		if len(self._cache)>=self._capacity:
-			self._cache.popleft()
-		self._cache.append(frame)
+	def put(self,item):
+		self._i+=1
+		if len(self._keys)>=self._capacity:
+			k=self._keys.popleft()
+			del self._values[k]
+		self._values[self._i]=item
+		self._keys.append(self._i)
+		return self._i
+
+	def get(self,k):
+		return self._values.get(k)
+
+	def getRelative(self,k):
+		return (self._keys[k], self._values[self._keys[k]])