Vorbis dev - Aug 2009 - Floor1 encode/decode and FLOOR1_fromdB_LOOKUP

Hello,

I have two questions concerning floor1 encoding/decoding. First I'll ask
about the FLOOR1_fromdB_LOOKUP table: what is it's purpose? Is it to convert
the amplitude differences between [floor1_Y] values to a dB scale? And, if
I'm right with that, here comes the 2nd question: when render_line0 is used
to encode floor1, then floor1_inverse2 must be used in decode (in order to
convert to dB scale), and, in the other hand, if render_line is used to
encode, then floor1_inverse1 must be used in decode (render_line converts to
dB and therefore floor1_inverse1 gets the amplitudes in dB). If all my
suppositions are right, is there any recommendation or something like that
to decide whether to use one combination or the other?

Thank you, and, sorry if I've lost my head with this.
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://lists.xiph.org/pipermail/vorbis-dev/attachments/20090821/3f4f168c/attachment.htm

On Fri, Aug 21, 2009 at 7:58 AM, Jes?s D?az
Vico<jesus.diaz.vico at gmail.com> wrote:
> Hello,
>
> I have two questions concerning floor1 encoding/decoding. First I'll
ask
> about the FLOOR1_fromdB_LOOKUP table: what is it's purpose? Is it to
convert
> the amplitude differences between [floor1_Y] values to a dB scale?
from a dB scale, not to.
> And, if
> I'm right with that, here comes the 2nd question: when render_line0 is
used
> to encode floor1, then floor1_inverse2 must be used in decode (in order to
> convert to dB scale), and, in the other hand, if render_line is used to
> encode, then floor1_inverse1 must be used in decode (render_line converts
to
> dB and therefore floor1_inverse1 gets the amplitudes in dB). If all my
> suppositions are right, is there any recommendation or something like that
> to decide whether to use one combination or the other?
...huh?  Completely lost too :-)

encoding and interpolation are done in dB, and then the resulting
curve is converted to linear.

Monty