[vorbis-dev] Re: [vorbis] Amplify Ogg files without decode/encode

[Monty]

On Wed, May 16, 2001 at 09:19:57PM +0300, Beni Cherniavsky wrote:
> On 11 May 2001, Mike Coleman wrote:
> 
> > Michael Smith <msmith at labyrinth.net.au> writes:
> > > I think it should be possible (though maybe difficult) to adjust volume
> > > without a full reencode. Not sure of details, though. Would need to read
> > > some source again.
> > 
> > It seems like it should be possible.  I was hoping, though, that there was
> > a constant stored in each frame that could be easily updated; it doesn't look
> > like it's that easy.
> > 
> How about just scaling all the codebook values?  Acording to your "Vorbis
> Illuminated" (which was very helpful to me ;), both the floor and the
> residue are encoded through the codebooks.  Then simply changing the
> codebook should scale the whole sound - or do I miss something like a
> logarithmic vs. linear difference in the meaning of the values encoded for
> the floor and the residue?  Also it will be lossless!

Floor 0 has a master amplitude value encoded in dB.  Just adjust it
per packet per channel.

Floor 1 will be no more complicated (although you'll have to add an
offset to all the values).

Monty

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