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Intro
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Apple announced Airplay (formerly known as AirTunes) as part of the iOS 4.2 update in September 2010
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It's all based on the original Remote Audio Output Protocol (RAOP) which was what AirTunes used.
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AirPlay Devices
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Senders
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iOS devices running 4.2 or later (iPod, iPhone, iPad) and iTunes
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Receivers
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Airport Express (audio), Apple TV 2 (video), 3rd party speaker systems
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Apple is licensing the audio and remote control portions to 3rd parties
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There is also the ability to remote control AirPlay devices using the Apple Remote app for iOS.
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Now connect via Home Sharing account on the Apple TV and iTunes
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Under AirTunes you had to use a code.
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There is also some amount of meta data contained in the stream because devices can display Song titles, artists, album names, elapsed and remaining time, and album artwork on their displays
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How it works
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There are two types of signals audio and video
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Video support was added as part of the transition to AirPlay
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Original version used
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AirPlay is a proprietary technology, but was cracked by Jon Lech Johansen (DVD John) in 2004
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It basically uses 3 core technologies. UDP, RTSP, and AES Encryption
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User Datagram Protocol (UDP)
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Send messages (datagrams, packets) to another device on an IP network without an implicit handshake
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Doesn't require messages to arrive in order, they can be duplicated, or not be there at all.
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Used for audio and video streaming because dropping and resending is better than waiting.
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Real Time Streaming Protocol (RTSP)
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A network control protocol used to control streaming media servers.
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The protocol is similar to HTTP, but has "state". Provides and identifier for the stream so it can keep track of individual streams.
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Important, especially if it has to track multiple streams.
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Each stream actually uses 2 RTSP streams. One is a control channel and the other is the data stream.
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Advanced Encryption Standard (AES)
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This is part of the proprietary part of Apple's Airplay technology
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The the encryption scheme they use to protect the streaming data and ensure it can only go to approved AirPlay receivers.
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They use a public/private key system.
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In April James Laird, extracted and published Apple's private key extracted from an Airport Express ROM.
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ShairPort project is a sample software AirPlay receiver.
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Stream contents
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Every stream has an associated RTP timestamp and a sequence number along with the data packets
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There are also sync packets that are sent once per second or when adding a speaker.
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Using AirPlay
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On iOS
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Look for the AirPlay icon in the player of an app
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Double Tap to bring up the background processes and swipe to the left (double swipe on iPod and iPhone). Airplay next to the volume and playback controls.
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In iTunes
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Airplay icon in the bottom right corner
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Remote App
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Airplay icon on "Now Playing" screen.
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There are APIs open to developers for adding AirPlay support to their apps.
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Future of AirPlay
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AirPlay Mirroring is a feature in iOS 5 using the iPad 2.
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Open Airplay up to a number of Apps that don't officially support it.
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Safari and Web apps specifically.
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iOS 5 has a number of AirPlay updates specifically related to video
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Airplay support for FaceTime
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Mirror Video Out (as if you connected with the cable adapter)
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Allows to have different content displayed on Apple TV and the iPad
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Great for Gaming
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This feature may open Airplay to many apps and
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Cool Airplay Tricks
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Cool tools from Erica Sudun
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Worked under Snow Leopard, not sure on Lion compatibility
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BananaTV (AirPlayer), Transform your Mac into an AirPlay-compatible display.
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AirFlick, Serve files and URLs to Apple TV
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Bruce, Display time, day, local weather, RSS-feeds, or live screen shots on ATV, among other features
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AirVideo Client, Bare-bones way to watch your AirVideo Server-supplied video on a Mac.
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Use Remote App to stream audio to multiple rooms
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Need to run from an iTunes Library, but can send to multiple receivers
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Launch the remote app and connect to iTunes source and start playing a file
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Press the Airplay button and check each destination you want to send audio to
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Can control the volume for each device separately.
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If you have more the 1 Mac you can control different sources and send the audio to different destinations.
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AirView was a cool iOS app that made your device into a receiver
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Rogue Amoeba
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AirFoil can send audio from your Mac to a compatible AirPlay device
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They also offer AirFoil speakers for Mac or iOS that lets you send audio to those devices.
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