Decode it in which app?
I took a look at the android version of the app and they are using a version of ffmpeg to decode the video. It shouldn't be hard to figure out the format once we can get the raw data from the camera. I know no way of doing that at present however.
My app, iOS. But useful info for anyone who wants to show video from the Tello in any application.
UPDATE: it will probably require passive packet sniffing as it would appears that the drone WiFi disconnects when more than 1 device tries to connect.
Also, I was unable to use a VPN based packet sniffer on my Android device as the Tello app was unable to connect to the drone when the VPN was running.
I am an app developer and my app is for iOS. I have developed an Apple Watch app that controls drones such as Mavic Air, Spark and Pro. I want to develop an app for the Tello and it is for the iPhone (iOS).