We had a small discussion at the german wikipedia about vorbis: it is able to produce fixed bitrate, or not?
I decided to ask the people at xiph.org because the owed me a favour (I helped them a little bit with their homepage), and fortunately Ralph Giles found the time to answer the question:
> there is a discussion at the german wikipedia
> about vorbis:
> we try to overwork the whole article and we are
> not sure at the moment if vorbis supports fixed
> bit rates nativly, or if only some vorbis-programs
> like oggenc support fixed bitrates through a kind
> of “hack” like setting minimum bitrate = maximum
Vorbis is natively variable bitrate, but an encoder is of course free to create a fixed bitrate stream if it wants to. This distinction may be the origin of your confusion.
The reference implementation, at least as of v1.1 does have true “fixed” bitrate support. Setting maximum=minimum with a VBR encoding mode doesn’t actually do anything.
> So do you know exactly how it is? Or do you know
> someone whom I could ask? And, btw.: now you
> have probably a new question for your FAQ 😉
Hope that helps. I’ve cc’d Monty, in case he wants to elaborate on my answer.
As usual I cannot post these information at the wikipedia because I do not have the rights to publish Ralph’s words under the gfdl – but this blog post will be enough, I hope.
If anyone wants to have more information (like the e-mail-address or something), feel free to ask.
And, for the record: there was no other answer by Monty 🙂