[vorbis] My Vorbis beta 2 impressions

[Thomas Marshall Eubanks]

Monty wrote:

> >
> > > Also, even though the ogg files are EXACTLY the same length as the original
> > > wav files, I can still hear a tiny <click> between songs that flow into one
> > > another. This doesn't happen always, some files come out fine, some have
> > > (more or less audible) clicks between them.
> >
> > When going from track to track, the transition is not 'lapped'.  frames in
> > Vorbis (like in mp3) are actually overlapping transforms, but between two
> > songs, obviously there is no overlap and because the compression is lossy (nad
> > the us the output an approximation) where there is no smooth overlap, the end
> > and beginning may not match up exactly.
> >
> > One could actually set up the encoder to pay more attention to this to make
> > sure that the approximation *does* match up on the other side...
>
> Actually, I just realized I may be doing something silly in the encoder that's
> seriously exacerbating the problem... IIRC, I'm padding end of song/end of
> frame with zeroes so that we have enough data for the last frame; Vorbis knows
> not to include these zeros at the end, but it does add a potentially large
> high frequency spike in the last frame which will spread and make the
> approximation much harder.  Eliminating that problem is both The Right Thing
> To Do and reasonably easy.
>
> Monty
>
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You could use a Gaussian or a Hanning window on the last 20 msec before the zeros.

                                   Regards
                                   Marshall Eubanks

   T.M. Eubanks
   Multicast Technologies, Inc
   10301 Democracy Lane, Suite 410
   Fairfax, Virginia 22030
   Phone : 703-293-9624
   Fax     : 703-293-9609

   e-mail : tme at on-the-i.com     tme at multicasttech.com

 http://www.on-the-i.com         http://www.buzzwaves.com

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