[Vorbis-dev] Re: Experimental Bitrate peeler

[Vinoth Kumar]

Hi Seghar, John,

Seghar and John - Thanks for your inputs.

    We have implemented this bitrate peeler primarily to test the new decoder developed by us. To put it in other words, bpeel is one of the 14 tools we developed and tested the decoder. So we didn't have really much of chance to check the bpeel as a tool and hence bpeel was released without much or no internal testing.

Now with inputs from different people on mailing lists, forums and emails we have found how much importance people give for a bitrate peeler without any noise ;-). This has kindled interest among our engineers to start working on bitrate peeler. Once we have some updates on our work on bitrate peeler we will post back the results.

Regards,
Vinoth



On Tue, 24 May 2005 Segher Boessenkool wrote :
> >      We need inputs with respect to results of this 
> bitrate peeler. 
> > This bitrate peeler reduces the bitrate by cutting 
> the packets based 
> > on the factor input provided by the user.
> 
> You mean, you peel every packet by throwing away the 
> same ratio of
> bits (or bytes, really)?  And with an unmodified 
> encoder?  Forget
> it, that is the second worst scheme possible (the worst 
> is throwing
> away all packet contents completely).  Been there done 
> that.
> 
> To do good peeling, you really need access to the 
> masking curves,
> and there is no way to reconstruct that (cheaply) from 
> the info
> in current Vorbis streams.  Well there is part of that 
> info in
> the floor curves, but the transform used (windowed 
> DCT-IV) plays
> nasty aliasing games, most easily heard in the upper 
> frequencies
> (but not even the worst there -- adaptive low-pass 
> algorithms
> can hide most of this).
> 
> >  Source code of this experimental bitrate peeler 
> comes along with our 
> > free trial version of the decoder.
> 
> I couldn't find it...  didn't look too hard, though.
> 
> Good luck, I really do hope you _do_ find a magic 
> bullet,
> 
> 
> Segher
>