Talk:Advanced Audio Coding

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[edit] MPEG-4 vs AAC Confusion

This article & the MPEG-4 article leave me very confused on what the actual relationship between AAC and MPEg-4 is! For example this article says:

"AAC is also the standard audio format for ... the MPEG-4 video standard."

While the MPEG 4 Article says:

"AAC (Advanced Audio Codec) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued."

Now what is a normal reader (like me) supposed to make of that? Is AAC a subset of the MPEG-4 standard? An example of the MPEG-4 standard? A model which was used to create the MPEG-4 standard? Is there such a thing as an independent MPEG-4 compression algorithm which isn't called AAC? The MPEG-4 article seems to imply that AAC was a separate standard that was pre MPEG-4. Any and all clarifications would be appreciated! LemonLion (talk) 13:03, 21 December 2007 (UTC)

Yes, it would be nice to get some clarification about that. My understanding: AAC is the name of the audio encoding technology specified in the MPEG-2 Part 7 standard (which differs substantially from the audio encoding technology specified in the MPEG-2 Part 3 standard). AAC is also the name of some subset (or class of subsets) of the MPEG-4 Part 3 standard. Now comes the hard part. Are there any differences between MPEG-2 AAC and MPEG-4 AAC? If so, what are they? If not, then why bother to standardize the same thing twice?

There also seems to be several AAC variants — called low-complexity AAC, low-delay AAC, enhanced AAC plus, HE-AAC, HE-AAC v2, etc. The exact relationship between these things seems somewhat difficult to ascertain. How many incompatible variants of AAC are there? What distinguishes something that is AAC from something that is not AAC? Do AAC decoder capabilities have some kind of nested structure? -131.107.0.73 (talk) —Preceding comment was added at 01:40, 20 May 2008 (UTC)