[vorbis] nominal bitrates

[Moritz Grimm]

Hi,

<p>apparently, I didn't delete my test samples ... I found them. :) Here's
a small table of what nominal bitrate fits to which quality at what
sample rate. Quality levels inbetween -1 and 0 are possible, but I
didn't test them. Nominal bitrates of those quality settings will be
somewhere between those of -1 and 0 and therefore can be guessed.

q/channels ||  -1/mono | -1/stereo ||  0/mono  | 0/stereo
 samp.rate ||          |           ||          |
-----------++----------+-----------++----------+-----------
   8000 Hz ||   8 kbps |   12 kbps ||  14 kbps |  18 kbps
  11025 Hz ||  12 kbps |   16 kbps ||  20 kbps |  26 kbps
  22050 Hz ||  16 kbps |   30 kbps ||  24 kbps |  36 kbps
  44100 Hz ||  32 kbps |   48 kbps ||  48 kbps |  64 kbps
-----------++----------+-----------++----------+-----------

32000 Hz sample rate is also a tuned set of modes, but doesn't give much
advantage over 44.1 kHz at those quality settings in terms of filesize.
I didn't make 32kHz test samples either, so this is an exercise for the
reader. :)

Note that on some clips, the average bitrate was very close to the
nominal bitrate, in some it wasn't at all. Nevertheless, those nominal
bitrates should show which --managed settings are supposed to work well
with a certain sample rate.

<p><p>Moritz

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