HE AAC Audio Quality & Tuning Options

[GreenSeer]

I am new to the lossy coding world. I recently became a DROID owner and, in an effort to get down to carrying one device, I ripped all of my music to my DROID at 64 kbps. In the environments I often listen in (Airports, Planes, Rental Cars, Taxi's, etc.) this is good enough for me and has the great benefit of using minimal storage space. The efficiency of a codec that provides satisfactory audio quality while using lower bitrates appeals to me.

My question is whether this codec is still being developed and "tuned"? I guess I am curious as to whether HE-AAC is now about as good as it will ever get. For example, is the crossover point from real sound to where the SBR begins as finely tuned as possible? Will we ever get to the point where a 48 kbps rip is perceived qualitatively by a general audience like a 128 kbps AAC file is today? Thanks!

[IgorC]

My question is whether this codec is still being developed and "tuned"?

Yes, Fraunhofer and Apple HE-AAC encoders have been updated not so long time ago. For HE-AAC ~64 kbps (variable bitrate VBR) I'd go with Fraunhofer encoder from the latest Winamp.

Will we ever get to the point where a 48 kbps rip is perceived qualitatively by a general audience like a 128 kbps AAC file is today?

No, that won't happen. Developers improve a quality of both HE-AAC and LC-AAC. HE-AAC is excelent for low bitrates. For bitrates more than 80 kbps use LC-AAC.
Some wiki articles about this format will be a good start.

This post has been edited by IgorC: May 23 2012, 17:36

[C.R.Helmrich]

For HE-AAC ~64 kbps (variable bitrate VBR) I'd go with Fraunhofer encoder from the latest Winamp.

Thanks a lot, I take that as a compliment Sounds like you have done a blind comparison on many items. Would you mind sharing a plot of your results, like you did in another thread? I'm interested in the names of the items where you feel the iTunes encoder is notably better than the one in Winamp. Maybe I or my colleagues can still do something about those.

Will we ever get to the point where a 48 kbps rip is perceived qualitatively by a general audience like a 128 kbps AAC file is today?

I agree with Igor. 48-kbps HE-AAC uses parametric tools for the high frequencies, which don't allow you to perfectly reconstruct the original spectrum. Anyone with normal hearing who concentrates during a comparison test will hear the degradation over the 128-kbps encoding, I would say.

Chris