Since reading this Ars Technica article, I've learned that the movies you can buy and rent in the iTunes Store (and directly from the Apple TV) include two audio streams: an 5.1 AC3 stream and a 2.0 AAC stream to fall back on in case a device is detected that can't decode AC3 audio. I have my Apple TV connected to my TV via HDMI. Of course, a 'dumb' TV can't decode AC3 audio. But I also run an optical cable from my Apple TV, directly into my AV receiver. This device obviously can decode an AC3 audio stream. Now, why does my Apple TV still default to 2.0 audio? Must the HDMI cable be connected be to an AC3-capable device? My receiver doesn't have any HDMI inputs or outputs, though. (As it slightly predates the standard.) So how do I go about getting the 5.1 AC3 audio stream to my receiver? When feeding my receiver movies only containing an AC3 audio stream from the FireCore Media Player, it works beautifully. So why don't Apple's own movies play nice for me as well? Any suggestions?