[Vorbis] oggenc adds severe distortion

[Ti Kan]

Hi all,

I routinesly rips my CDs to WAV and then convert to ogg vorbis format
for use in my car and portable player.  I don't usually notice anything
amiss, but on the last track of Mike Oldfield's "Music of the Spheres"
album ("Musica Universalis", at the very end crescendo), the converted
.ogg file exhibits terrible distortion (sounds like digital clipping).
This does not occur with MP3 or WMA formats.  I used a quality factor of 4.

Does oggenc raise the amplitude (to cause digital clippiing)?  Any
idea why this happens?

Also, my previous experience with ogg vorbis format is that it provide
nice, seamless gapless transitions between tracks.  However, on this
same Mike Oldfield album, I can hear a click and discontinuity between
certain tracks.  Since this is a continuous symphonic piece that
spans across tracks, this is annoying.  What is it with this album
that taxes the capability of the vorbis encoder?

-Ti