[vorbis] APPLAUD.WAV problems
greg at linuxpower.cx
Sun Feb 17 18:01:14 PST 2002
On Sun, Feb 17, 2002 at 05:29:20PM -0500, Ed Sweetman wrote:
> before you go throwing the entire mail away I would suggest encoding
> absolute silence. It's fun, especially when you get about the same
> bitrate as the cd audio clips you're encoding at the same quality
> level. The evidence seems to be pointing at a lower bound being set by
> the quality level and a detailed look at every single block shows that
> there's a mysterious lack of bitrates below around the 128kbit range in
Step away from the crack pipe. If you are going to run around with such
strong thoughts on the operation of Vorbis, please do yourself a favor and
actually learn something about the operation of Vorbis.
First off, true absolute silence (i.e. digital silence) will get encoded at
<3kb/sec no matter what your -q level is.. If you were seeing higher
bitrates then that, then you were not actually encoding true silence but
rather low level noise.
Because of the way the Vorbis works internally, it computes the masking
thresholds as though the loudest sound it has heard over a time window is at
the human pain threshold (I think, whatever, it pretends it's really loud).
If you encode nothing but quiet noise, you'll get a fairly high bitrate.. If
that noise is surrounded by actual music, then the quiet noise will get
encoded with a fairly low bitrate.
This overcomes a major weakness of many VBR codecs: They don't use enough
bits on quiet content as they make the incorrect assumption that the listeners
can barely hear it (mistaken because the listener will turn up the volume
So, stop playing the conspiracy theorist. You've got the source, get
someone you trust to check: There is no knowledge of bitrate in -q modes. :)
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