Just a bit of Audioholic musing here, why wasn't AAC ever considered for the DVD standard? Unlike Blu-ray, one of the major issues with DVD was limited space. Considering the limited storage options of the time, coupled with the relatively inefficient compression schemes of the day vs now, high quality digital video consumed a massive amount of space, even at SD resolutions, and mpeg2 compression kinda sucked compared to h264 (which can almost transparently compress a 2 hour SD movie into a 1-2gb file), so audio had to leave plenty of space for video.
AAC was created and added as a standard to mpeg2 around the same time when the first dvd players were coming out. Dolby digital was already and aging format, first used in 1992 in the cinema with Batman Returns. As anybody who payed attention to the evolution of digital audio and video knows, old turn of the century formats were pretty bad. mp2 audio sucks below 320kbps stereo, most of the compression schemes of the day completely mangled audio at lower bitrates, and even mp3 in it's early years wasn't great, a 128kbps mp3 back then was glaringly full of artifacts, using the latest version of lame, it's sometimes hard to tell. AAC has always been a superior format. I still have some of the old original Itunes 128kbps downloads and none of them sound too bad. Doing a blind test between the two using a DTS MA file demuxed from an MKV file, and then converted via FFmpeg to both ac3 at 448kbps and AAC at 384kbps, it's obvious 64kbps per channel AAC (i.e. your typical 128kbps music file) sounds immensity better than Dolby Digital, even at a lower bitrate.
Unless you used PLIIx back in the DVD days to extract rear surround channels from 5.1 content, a majority of movies were limited to 5.1, with the occasional discrete DTS-ES movie. Dolby digital doesn't support discrete 6.1, let alone 7.1. AAC support a ridiculous 48 full bandwidth channels and up to 16 LFE channels. At a bitrate hardly higher than 448k DD, an AAC track could provide 7.1 audio at 512kbps and sound better than ac3 while doing so. as an added bonus, AAC supports variable bitrate encoding, meaning if 512kbps isn't needed all the time, space could be saved, where it's not enough, it could increase. I'm fairly positive AAC also supports features like Dynamic range compression as well.
Either I'm missing the reasoning or it truly was just a bad decision (or perhaps a financially guided decision) to use AC3 as the defacto standard on DVD's.
