[vorbis] APPLAUD.WAV problems
ed.sweetman at wmich.edu
Sun Feb 17 14:29:20 PST 2002
On Sun, 2002-02-17 at 16:53, Gian-Carlo Pascutto wrote:
> ----- Original Message -----
> From: "Ed Sweetman" <ed.sweetman at wmich.edu>
> To: <vorbis at xiph.org>
> Sent: Sunday, February 17, 2002 10:39 PM
> Subject: Re: [vorbis] APPLAUD.WAV problems
> > The reason applaud.wav is a problem (if it is at all anyway) is that
> > there is an upper and/or lower bound bitrate setting for quality modes
> > for vbr encoding
> This is not true, the encoder does no such thing.
Yes it is, you should run some actual tests and see for yourself.
<p>> Moreover, the problem is that the encoder is not aware that it is
> creating artifacts, so it will not use a higher bitrate because it
> does not realize something is wrong, i.e. it's psymodel is not
> perfect (this also pretty much invalidates your entire mail)
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
ogg files encoded at -q 5 Now you might be quick to jump and say, well
you need at least that to keep the stereo lossless and I really have no
evidence to counter that. But then I'd be quick to show you that -q 4.99
exibits the same exact behavior as only the lower bound bitrate is a bit
lower, around the 112kbit range.
So yes the psymodel is not perfect and that's why artifacts are falling
through the cracks, by VBR algorithm I was also talking about the
psychoacoustics it used to decide what to do with an audio sample. But
there also seems to be a lower bounds being put on files regardless of
the need to use such a bitrate to achieve the quality setting, whether
by hardcoding or by effect, it's still there.
<p>--- >8 ----
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