|Type||Wireless Media Streaming|
|Release date||September 1, 2010; November 22, 2010 for iOS systems|
AirPlay (previously called AirTunes when it was for audio only) is a proprietary protocol stack/suite developed by Apple Inc. that allows wireless streaming of audio, video, and photos, together with related metadata between devices. Originally implemented only in Apple's software and devices, Apple has licensed the AirPlay protocol stack as a third-party software component technology to manufacturer partners for them to use in their products in order to be compatible with Apple's iDevices.
Starting with Apple TV firmware 6.0, the encryption scheme "FairPlay" is enforced and devices not supporting it can't be used.
|This section requires expansion. (June 2012)|
AirTunes was originally released on June 7, 2004.
The enhancements to the AirTunes technology and the subsequent name change to AirPlay were announced by Apple CEO Steve Jobs at the iPod event on September 1, 2010, and explained thus:
“Now, what is AirPlay? You know what AirTunes is… listen to music from all over your house from your mobile device”, said Jobs. "We’re changing the name of AirTunes to AirPlay, and it’s not just music anymore. You can stream all kinds of media anywhere in your house."
There are two types of AirPlay devices: those that send audiovisual content, and those capable of receiving the content and rendering it on displays and speakers.
AirPlay sender devices include computers running iTunes, and iOS devices such as iPhones, iPods, and iPads running iOS 4.2 or greater. OS X Mountain Lion supports display mirroring via AirPlay on systems containing 2nd generation Intel Core processors or later.
AirPlay receiver devices include AirPort Express (which includes an analog and optical SPDIF audio output connector), Apple TV, and third party speakers. With the open source implementations of the AirPlay protocol any computer can now be turned into an AirPlay receiver.
AirPlay wireless technology (receiver mode) is integrated into speaker docks, AV receivers, and stereo systems from companies such as Bose, Yamaha, Philips, Marantz, Bowers & Wilkins, Pioneer, Sony, and Denon. Song titles, artists, album names, elapsed and remaining time, and album artwork can appear on AirPlay-enabled speakers with graphical displays.
Bluetooth devices (headsets, speakers) that support the A2DP profile also appear as AirPlay receivers when paired with an iOS device; Bluetooth is a device-to-device protocol that does not rely on a wireless network access point.
AirPlay allows an Apple TV or AirPort-enabled computer with the iTunes music player to send a stream of music to multiple (three to six, in typical conditions) stereos connected to an AirPort Express or Apple TV.
Speakers attached to an AirPort Express or Apple TV can be selected from within the "Remote" iPhone/iPod Touch application, allowing full AirPlay compatibility (see "Remote control" section below).
The AirTunes part of the AirPlay protocol stack uses UDP for streaming audio and is based on the RTSP network control protocol. The streams are transcoded using the Apple Lossless codec with 44100 Hz and 2 channels encrypted with AES, requiring the receiver to have access to the appropriate private key to decrypt the streams. The stream is buffered for approximately 2 seconds before playback begins, resulting in a small delay before audio is output after starting an AirPlay stream.
The protocol supports metadata packets that determine the final output volume on the receiving end. This makes it possible to always send audio data unprocessed at its original full volume, preventing sound quality deterioriaton due to reduction in bit depth and thus sound quality which would otherwise occur if changes in volume were made to the source stream before transmitting. It also makes possible the streaming of one source to multiple targets each with its own volume control.
AirPlay Mirroring is a slightly different technology that allows specific content to be broadcast from a variety of iOS devices and iTunes to a second generation Apple TV. The exact composition of the protocols that AirPlay Mirroring uses have not yet fully been discovered, or reverse-engineered. However, an unofficial AirPlay protocol specification is available. A 2nd generation or later Apple TV is required, and supported hardware (when using OS X Mountain Lion or later) includes the iMac (mid 2011 or newer), Mac mini (mid 2011 or newer), MacBook Air (mid 2011 or newer), MacBook Pro (early 2011 or newer) and the Mac Pro (late 2013 or newer).
The AirPort Express' streaming media capabilities use Apple's Remote Audio Output Protocol (RAOP), a proprietary variant of RTSP/RTP. Using WDS-bridging, the AirPort Express can allow AirPlay functionality (as well as Internet access, file and print sharing, etc.) across a larger distance in a mixed environment of wired and up to 10 wireless clients.
Reverse engineering AirTunes and AirPlay
On April 8, 2011, James Laird reverse-engineered and released the private key used by the Apple AirPort Express to decrypt incoming audio streams. The release of this key means that third-party software and devices modified to use the key will be able to decrypt and play back or store AirPlay streams. Laird released ShairPort as an example of an audio-only software receiver implementation of AirPlay.
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- The Main Wireless HDMI Transmission Protocols and Their Typical Products Comparison of different wireless HDMI transmission protocols at Portablehifi.com