[vorbis] Re: Re: fitting lots of music into 10GB with Vorbis

Carsten Haese carsten at uniqsys.com
Tue Dec 31 08:31:21 PST 2002

On Tue, 2002-12-31 at 00:39, Martin Blackwell wrote:
> It would be very nice if someone could take a look at the "bitrate.js" file
> and point out where the maths is wrong.

Your linear interpolation between the known points looks very fishy. The
equation that describes a straight line going through the points (x1,y1)
and (x2,y2) is y = (x - x1) * (y2 - y1) / (x2 -  x1) + y1

For the first segment, plug in x1 = -1 (or whatever value represents
quality -1), x2 = 0, y1 = 45, y2 = 64. For the second segment, plug in
x1 = 0, x2 = 1, y1 = 64, y2 = 80. Et cetera.

Note that the vertical offset (the + y1 in the formula) changes from
segment to segment. In your formula, the vertical offset is always 'q0',
i.e. 64, which is increasingly wrong the higher the bitrate gets.

I hope this helps,


<p>--- >8 ----
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