Bug#584313: Vorbis libraries (libvorbis, libvorbisenc, libvorbisfile) _must_ be updated as a set; not always happening

[Monty Montgomery]

Package: libvorbis0a, libvorbisfile3, libvorbisenc2
Version: 1.3.1-1

We had a user stumble into #vorbis with Debian Unstable oggenc that
produced corrupt Vorbis files.  Investigation revealed that he still
had an ancient libvorbisenc (.so.2.0.3) installed along with a fully
up-to-date libvorbis0a-1.3.1-1 and vorbis-tools 1.4.0.  The package
system was aware of the old install, but the package depends were
satisfied (incorrectly), so nothing triggered pulling in a required
matching libvorbisenc2. This is possibly because his libvorbisenc
likely predated the libs being split into seperate packages.
Libvorbis0a does not force an update of the other libs/packages, and
the older libs were still satisfying the >= depends of the tools
packages.

The package system was fully aware of the presence of the old
libvorbisenc (from a several year old 1.2 release), and explicitly
installing libvorbisenc2 restored his Vorbis install to functional.

To be clear: libvorbis, libvorbisfile and libvorbisenc share
internally defined structures and data, and they must be upgraded as a
matching set.  Older packages apparently are still satisfying package
depends, and preventing correct automated update to the new
split-packaging.  The split-packaging must indicate conflicts for the
older monolithic lib package (and perhaps older split packages if
their dependencies were similarly broken), which it does not appear to
do.

Monty
Xiph.Org