#384 Non audio ogg files normalised with Ogg Audio normaliser

[Terry O'Neill]

Currently it appears that any ogg file will be normalised with the Ogg Audio normaliser. As ogg is just a container format and can contain such things as video or text this is not desireable. In cases where the Ogg Audio normaliser cannot recognise the content (and it appears to only recognise content where the first stream is a Vorbis, Flac or Speex encoded audio stream) then it will binary normalise the file internally (using the BinaryToXenaBinaryNormaliser). This should be changed so that the Ogg Audio normaliser is only used for ogg files where the most significant steam is audio. Other ogg files should either get their own normaliser or use the binary normaliser.