[vorbis] [new?] Streaming technique

Alex Iribarren ogg at iribarren.com
Wed Jun 6 03:46:37 PDT 2001

Before I start, I just want to say that I know very little about audio
compression or signal analysis. And I have no clue what a Lorentzian 
is, but
I guess it must be some way of mesuring a signal. How is nonlinear
compression done?

If I have understood correctly both of Dr. Joerg Bergmann's messages,
technique I have suggested is impossible because there is no redundancy 
in a
128kbps stream and a 64kbps one, meaning that you can't extract the 
data from the 128kbps stream to reduce it to 64kbps. Is this actually 

However, if that is not possible, perhaps you can overcome the nonlinearity
problem by splitting the streams before actually compressing them
nonlinearly. When reducing redundancies in the sound file to encode, and
when applying the perceptual filters, you could apply them in different
degrees to both streams (lots of filtering for the 64kbps stream,
and half
the filtering for the 128kbps stream). After that, you could "substract" 
64kb stream from the 128kb one to obtain the 64kb of sound that was 
from the original 64kb stream. Then you would actually do all the 
rest of
the compression.

> But such thinking is invalid for nonlinear mechanisms.
> I will give an explanation from my science:
> Given any curve, I may fit it with a set of 5 Lorentzians
> or, for more accuracy, with 10 Lorentzians. Doing so, the
> resulting 10 Lorentzians _wont_ include the less accurate
> 5 Lorentzians as a subset! Of course, you may construct
> such a fit, but it will waste accuracy (or, in ogg:
> bandwidth for the same quality).
> J"org Bergmann
> email at jbergmann.de

As to what Kristoff Bonne <kristoff.bonne at skypro.be> said, I think that
would simply be a matter of syncronizing the streams through buffering,
much more difficult that what is actually done now with webcasts.

>Two remarks (to continue this brainstorming-session):
>- One of the things you should take care of; is that both 'streams' 
>have the same bitrate (or a bitrate that does not vary to much vis-
>What I mean is this:
>If the 2nd session that is started is an (additional) TCP-session;
>have to deal with the 'slow start'; having a quite varied bitrate 
at the
>start of the session.

--- >8 ----
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