objective measurement of HE AAC
Reply #9 –
HE AAC is a lossy codec, and one that doesn't really aim to be transparent (the HE is for High Efficiency, meaning it's meant to get "good enough" quality into a very low bitrate stream or small size file).
... or in other words, HE-AAC uses parametric tools which don't preserve the original waveform(s) of the coded signal. Neither does error concealment (since it can only estimate the actual waveform).
And this is what causes problems with objective measures like PEAQ.
It is built on psychoacoustic principles and listening tests.
So are objective measures like PEAQ (which was trained to reflect a large set of listening test scores). This works sufficiently well at high bit-rates where parametric
coding is not used (I think in Muaddib even improved it once during his Master's thesis, here is the link). But HE-AAC was finished after PEAQ had been standardized,
so it doesn't have any measures for non-waveform-preserving coding (it compares against the original waveform and finds large errors = bad scores, even though
the parametric coding may sound very good).
So, I don't know of any tool for meaningful objective measurement of HE-AAC.
Chris