[vorbis-dev] Thought for the new year

Segher Boessenkool segher at wanadoo.nl
Wed Dec 27 16:57:27 PST 2000

Gregory Maxwell wrote:
> On Thu, Dec 28, 2000 at 01:11:00AM +0100, Segher Boessenkool wrote:
> > By "good for coding" I don't mean quality, of course; we're talking
> > about a transform for compression here, so a "good" transform is one
> > that makes it easier to compress, i.e. it should group the features
> > of the sound together based on some sensible norm. MDCT uses a window
> > that doesn't change size for differing frequencies; that's no good for
> > a perceptual codec.
> But it is quite good from a pure lossless, compact representation
> prospective.

I disagree. Look at what a MDCT does to an attack... It gets a very
flat spectrum. That's no good. You want smaller (effecetive) windows
at higher frequencies to adjust to the highly dynamic range of sound.
For video, ou don't care that much, as in the presence of bright
pixels, the dim pixels will be invisible; in audio, this is true only

> Ideally what you want to model is the human perceptual response to signal.
> All we need to do is take a living human ear, and the appropriate 'chunk of
> brain', plug it's output back into the computer to create a 'human ear
> transform'. :)

That would be great, as you would get _very_ low bitrate; but the
problem would be the inverse transform :-(



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