apple AirPlay, AirPort

AirPlay (previously called AirTunes when it was for audio only^[1]) is a proprietary protocolstack/suite developed by Apple Inc. that allows wireless streaming of audio, video, and photos, together with related metadata between devices. Originally only implemented in Apple's software and devices, Apple has licensed the audio-streaming portion of the AirPlay protocol stack as athird-party software component technology to manufacturer partners for them to use in their products in order to be compatible with Apple's iDevices.


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AirPort

Main article: AirPort

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.^[30]

Speakers attached to an AirPort Express or Apple TV can be selected from within the "Remote" iPhone/iPod Touch application, allowing full AirPlay compatibility^[31] (see "Remote control" section below).

[edit]Protocols

The AirTunes part of the AirPlay protocol stack uses UDP for streaming audio and is based on the RTSP network control protocol.^[32] 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.^[33]

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, nor reverse-engineered.^[4]

The AirPort Express' streaming media capabilities use Apple's Remote Audio Output Protocol (RAOP), a proprietary variant of RTSP/RTP. Using WDS-bridging,^[34] 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.

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