Mark Taylor wrote:
> >
> > 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.
>
I disagree (unless I missed something): with ABR, the user has to give an a priori bit
rate. This bit rate -10% is used as the default to encode most of the frame, _even_ if
they actually would require less bits.
A true VRB mode is for me a mode where the user doesn't refer at all to a bit rate,
but rather to a desired quality. The encoder then chooses the appropriate bit rate
-without any restriction- to reach this quality. Hence, both old and new (-Y) lame's
VBR modes are true VBR, but ABR is not.
Pierre
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