Nathan Froyd at Mozilla noticed something odd in the libvorbis sourcebase. Codebook 'length lists' only use integers in the range of 0 to 32. Well, worse than integers, actually, longs. And the lengthlists are big; the static data comprises the bulk of libvorbisenc.
In the earliest days of Vorbis development 15 years ago, codebooks were constructed differently and the lengthlists were quite small. Longs still weren't necessary, but the wasted space was negligible. When the coding strategy shifted and these lists became much larger, no one caught the wasted space. The vast majority of optimization was always for speed, not space. The only concentrated effort in trimming Vorbis library size down over the past decade had been in the decoder.
But now browsers need to ship encoders, and size matters. Add that to 64 bit taking over (and doubling the wasted space in the lengthlists), someone finally noticed the oversight.
That's a long way of saying "Xiph.Org is pleased to announce the release of libvorbis 1.3.4..."
No functional changes, but the encoder lib is now a shade over 25% the size it was in the 1.3.3 release.