[BC] AAC+ stream

[Goran Tomas]

On Tue, Mar 10, 2009 at 4:15 PM, Dana Puopolo 
<<mailto:dpuopolo at usa.net>dpuopolo at usa.net> wrote:
I also put up a 96 kbps AAC+ stream. Here's the URL:
<http://barix.b2netsolutions.com:8030>possiblefraudstart 
"barix.b2netsolutions.com30" possiblefraudend 
http://barix.b2netsolutions.com:8030

If you can afford 96 kpbs, for best sound quality it needs to be AAC, 
not AAC+. I guess it's a tiny difference in labelling so it often 
gets misinterpreted, but it's a significant difference in sound. Let 
me clarify a little bit.

AAC - Advanced Audio Coding
This is the "waveform" perceptual codec, similar to MPEG Layer I, II 
and III but more efficient. It's roughly 30% more efficient (better) 
than the (in)famous MP3 and according to some listening test, 
achieves transparency at 128 kbps.

HE AAC - High Efficiency AAC
This is the SBR enabled codec that uses AAC as the core codec. This 
means that the low band is coded with AAC, whilst the high band is 
only described with low bit rate data and re-generated (artificially) 
in the decoder. The HE AAC also goes under other labels such as 
aacPlus, AAC+ and Dolby Pulse, which all mean the same thing. It 
seems like there is a growing perception that this is the best 
perceptual codec out there, which is only partially true. It's best 
for very low bitrates, but it's not best when bitrate goes up.

Because HE AAC uses SBR, it sounds very good at very low bitrates. 
This is due to fact that HE AAC keeps the wide frequency response 
(thanks to SBR technology) unlike "normal" waveform codecs that low 
pass filter audio at these low bitrates to reduce artifacts and 
therefore sound muffled. However, at higher bitrates (96 kbps and 
above) the waveform codecs such as AAC have wide enough frequency 
response (cca 16k) and sound better than SBR codecs, because the high 
end is not re-generated and shaped in the encoder and therefore 
sounds more natural and has less artifacts.

So, for best audio quality (at this bitrate) I would suggest you 
switch to AAC. Look for AAC LC (low complexity) in the WinAmp.

Regards,
Goran Tomas