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Vorbis RC3 quality settings
Jon Ingram
post Dec 22 2001, 15:42
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RC3 is almost ready to do, and now has two ways to specify encoding:
1) -m minimum -M -maximum b nominal
2) -q quality

The quality indication goes from 0, which is nominally 64 kpbs, to 10, which is nominally 480kpbs, and is a floating point number.

To get some indication of how bitrate changes as you change the quality setting, take a look here:

http://www.maths.warwick.ac.uk/~jingram/ogg/

I (along with xercist from the #vorbis IRC channel) graphed bitrate-vs-quality for several well known samples, including hard-to-encode ones such as applaud.wav and fatboy.wav. The overall graph is as follows:

http://www.maths.warwick.ac.uk/~jingram/ogg/group.png

The big jump at q=5 is mainly down to the switching to lossless channel coupling. You'll also notice that the bitrate for q=n.99 is generally *larger* than that for q=n+1-- this is because the same settings are used for q in [n, n+1), and they are tuned for the lower end of that range.

Have fun.
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