>
> Shawn Riley wrote:
> >
> > Hi. I have a couple of my own questions about this.
> >
> > It sounds like what's being referred to as "ABR" would be not only faster,
> > but more reliable (in quality terms) than the traditional VBR. So what's
> > the use of traditional VBR now?
>
>
> >From the previous postings, it turns that ABR is not a true variable
> bit rate encoding. It is a compromise between constant bit rate and
> variable bit rate.
>
I think both modes are true VBR modes, but one picks the
bitrate based on perceptual entropy, and the other picks
the bitrate based on quantization noise vs allowed masking.
In Vorbis, the data is quantized and compressed at the same time, with
"vector quantization". The bitrate just depends on which codebooks
are used for the VQ step. Right now the codebooks are chosen (and
fixed) in advance after some number crunching on a large set of
typical .wav's.
Mark
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