HE-AAC vs AAC (was e: Breakaway Advice)
satech said:
There is usually a delay after starting the stream or tuning in the HD channel before the SBR kicks in, and before it does I can hear that the audio is more narrowband but also much less artificial-sounding.
Yes, that's exactly what I'm talking about! Until the SBR kicks in, you are only hearing the low band which is encoded with AAC but at half sample rate, so the response is roughly up to 8 kHz. The SBR then fills the rest of the spectrum (the high band) but as it is artificially re-generated, it always has that metallic sound to it. It never has the fidelity to the source material.
Especially with "troublesome" program material (bells, tambourines, muted trumpets, etc.) I'd rather hear smooth 7 or 8 kHz audio than sizzly, screechy 15 kHz audio.
Well that makes two of us
Let me again clearly state that no other codec performs better than HE-AAC, at very low bitrates. This IS the best codec for
very low bitrate streaming.
But at higher bitrates (96 kbps and above) there are better codecs, such as the AAC on its own. It's unfortunate that HE-AAC wasn't made scalable, so that at certain (high enough) bitrate, the SBR is turned off. The way they made it, HE-AAC always has replicated high frequencies, even if the bitrate is high enough that AAC alone would do a better job.
From my extensive listening to these codecs, that threshold bitrate is 96 kbps. Up to 64 kbps HE-AAC sounds better, but at 96 kbps and above, AAC is much more natural and faithful in the high frequencies and practically artifact free.
Even at 96 kbps, but especially at 128 kbps, AAC sounds amazing - better than analog FM radio, what should have been the goal of any digital radio transmission, if you ask me. HE-AAC aka aacPlus (aka AAC+) can never sound as good.
Regards,
Goran Tomas