[vorbis-dev] FLOOR_fromdB_LOOKUP

[Monty]

On Fri, Oct 12, 2001 at 07:17:01PM +0200, Attila Padar wrote:
> Hello,
> You know, I always worry about the precision
> and the float constants... and there is a large
> lookup table in the floor1.c ... and I figure out
> a way to keep the code size and speed, but
> to improve the precision at this lookup table.

The values listed are official and not to be changed.  Any
modifications of these values will render decode of already existing
files incorrect; encode and decode must match as exactly as machine
representation permits for correct results.

(If your encoder and decoder match, then they'll be compatable, but
your encoded files will decode incorrectly in the rest of the Vorbis
universe).

BTW, these constants are used to render floor1 in both encode and
decode; modifying them to 'better precision' will *not* improve
encoding quality (although you may think so because you might be
defeating the noise floor level by derating these constants.  You
could do the same by offsetting the noise through the psychoacoustics
settings).

> (the difference is small, but audible)

An audible difference == 'incorrect decode'.  Please do not mess with
these mandatory constants in search of greater quality.

Monty

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