<div class="gmail_quote"><div class="gmail_quote">2009/11/11 <span dir="ltr"><<a href="mailto:xiphmont@xiph.org" target="_blank">xiphmont@xiph.org</a>></span><div class="im"><div> </div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
This mostly restates the same idea several different ways that are<br>
equivalent and I'm not sure where you're confused. So let's step back<br>
a second...<br>
<br>
The floor encodes a continuous function and the values of that<br>
function are meant to be used as multipliers/ratios. Linear floor<br>
multiplied by residue gives you a spectrum.<br>
<br>
The floor is encoded on a logarithmic scale (not actually decibels in<br>
fact, but decibels are easy to understand, so the spec discusses this<br>
in terms of decoding the encoded floor to decibels, then doing a<br>
decibel->linear conversion). Unitless decibels are just ratios. 1 ==<br>
0db, 2 == 6dB, 4 = 12dB. The coversion is a simple 20log10(linear).<br>
<br>
Is that helpful?<br>
<br>
Monty<br>
</blockquote></div></div><br>Hm... I think I could summarize better my doubt in this way:<br>
<br>
Why the greatest value the floor can have, after converting it to linear, is 1 (which would make 20log10(linear) = 0, as linear is 1)? If the floor is the superposition of tonal
and noise masks, then, if it's greatest value is 1, or 0 dB, wouldn't
it be many mask values that it couldn't represent? (for example, if the
masks superposition equals to 10dB...).<br>
<br>
Again, this is why I thought of the reference level used in the "dB" scale to be dynamic with frequency (the mdct coefficients).<br></div>