En till artikel, denna gång om AirTunes:
MacWorld Editors' Note Weblog: How AirTunes Works
Intressant om hur det fungerar. Det är alltså Apple Lossless som strömmar och endast det. iTunes gör jobbet genom att göra om strömmen till just Apple Lossless. Och vill man strömma AC3 eller DTS så packas det i en Apple Lossless-ström som sedan dekodas av AirPort Express och skickas som äkta ACS/DTS optiskt till stereon. Nice nice...
Här är ett utdrag ur artikeln:
So I managed to finagle 15 minutes with Greg Joswiak, Apple's Vice President of Hardware Product Marketing, to talk about the new AirPort Express, and he managed to give me a good deal of detailed information about how AirTunes works.
Essentially, AirTunes is a method of creating remote speakers for a copy of iTunes, and sending data to those remote speakers via a wireless network. That network can be formed by connecting an AirPort Express to another AirPort Express, to an AirPort Extreme Base Station, or even to a non-apple 802.11b or 802.11g access point.
When you select an AirPort Express device in the new pop-up menu at the bottom of the iTunes 4.6 interface, that device essentially replaces your Mac's speakers as the audio-output source for whatever you do in iTunes. At that point you can do anything you'd normally do in iTunes -- play music from your Library, from someone else's library, or from your iPod; play an Internet radio stream; even play an audiobook. The sound won't come out of your Mac -- it'll come out of the speakers attached to the AirPort Express.
For those wondering if AirPort Express supports MP3, AAC, or any other specific file formats, the answer is no. AirPort Express supports Apple's Lossless Compression technology -- and everything that your iTunes streams across the network to Airport Express is compressed using that technology.
iTunes does the heavy lifting. When iTunes plays back standard audio content (AAC, MP3, audiobooks, music streams), it decompresses those file formats and creates what's essentially a raw, uncompressed audio stream. That stream is compressed on the fly using Apple's Lossless Compression, encrypted, and sent to the AirPort Express. AirPort Express decrypts the stream, decodes it, and outputs it in either analog format (if you plug in a standard analog mini jack) or as a digital PCM stream (if you plug in a mini-sized optical cable, which you can get from most major cable suppliers or straight from Apple for $39).
If iTunes is playing back a digital multichannel file format like AC3 (Dolby Digital) or DTS, those bitstreams are wrapped in Apple's compression and encryption, and then decoded at the other end. In those cases, AirPort Express would end up streaming the raw AC3 or DTS stream via an optical cable to your home theater receiver for decoding.
