diff --git a/tiny_streamlit_webrtc/__init__.py b/tiny_streamlit_webrtc/__init__.py
index 9bc7017..37f41e2 100644
--- a/tiny_streamlit_webrtc/__init__.py
+++ b/tiny_streamlit_webrtc/__init__.py
@@ -4,7 +4,9 @@
 import os
 import queue
 import streamlit.components.v1 as components
-from aiortc import RTCPeerConnection, RTCSessionDescription
+import cv2
+from av import VideoFrame
+from aiortc import MediaStreamTrack, RTCPeerConnection, RTCSessionDescription
 
 import SessionState
 
@@ -26,11 +28,37 @@
 session_state = SessionState.get(answer=None, webrtc_thread=None)
 
 
+class VideoTransformTrack(MediaStreamTrack):
+
+    kind = "video"
+
+    def __init__(self, track):
+        super().__init__()  # don't forget this!
+        self.track = track
+
+    async def recv(self):
+        frame = await self.track.recv()
+
+        # perform edge detection
+        img = frame.to_ndarray(format="bgr24")
+        img = cv2.cvtColor(cv2.Canny(img, 100, 200), cv2.COLOR_GRAY2BGR)
+
+        # rebuild a VideoFrame, preserving timing information
+        new_frame = VideoFrame.from_ndarray(img, format="bgr24")
+        new_frame.pts = frame.pts
+        new_frame.time_base = frame.time_base
+        return new_frame
+
+
 async def process_offer(pc: RTCPeerConnection, offer: RTCSessionDescription) -> RTCPeerConnection:
     @pc.on("track")
     def on_track(track):
         logger.info("Track %s received", track.kind)
-        pc.addTrack(track)  # Passthrough. TODO: Implement video transformation
+        if track.kind == "audio":
+            pc.addTrack(track)  # Passthrough
+        elif track.kind == "video":
+            local_video = VideoTransformTrack(track)
+            pc.addTrack(local_video)
 
     # handle offer
     await pc.setRemoteDescription(offer)