Since its inception in 2004 as AirTunes, Apple’s AirPlay protocol has served as the de facto standard for wireless audio streaming within the Apple ecosystem. For over a decade, the protocol was strictly bound to two-channel stereo, utilizing a combination of RTSP (Real Time Streaming Protocol) for control and RTP (Real-time Transport Protocol) for data transport. The audio was typically encapsulated within the Apple Lossless Audio Codec (ALAC) or encrypted AAC, providing high fidelity but limited spatial resolution.
AirPlay streams utilize FairPlay Digital Rights Management (DRM). The audio packets are encrypted using AES-128 in CBC (Cipher Block Chaining) mode. This requires the receiver to possess the necessary decryption keys, ensuring that only authorized hardware can decode and playback the multichannel stream. airplay 5.1