[Vorbis-dev] How to specify sample sizes?

[Nico Sabbi]

Hi,
quoting the vorbis doc
"Vorbis frames may be one of two PCM sample sizes specified during codec 
setup. In Vorbis I, legal frame sizes are powers of two from 64 to 8192 
samples. Aside from coupling, Vorbis handles channels as independent 
vectors and these frame sizes are in samples per channel."

I want to explicitly specify the sample size, so, how can I do it?
Can I set min_size == max_size?
If so, is there any disadvantage? which ?

Thanks,

    Nico