What is the maximum bitrate at which Vorbis can be encoded?
Theoretically, there isn’t one. Vorbis is tuned for bitrates of 16kbps to 128kbps PER CHANNEL. But there’s nothing in the spec that says you can’t encode a file at 512kbps or 8kbps. The current encoder supports the following bitrates: 64-500kbps stereo and 32-256kbps mono (at 44.1kHz sampling rate). Lower bitrates will be officially available in future versions.