I want to know the answer to the following question:
Which type of decoder must support bitrate switching on a per-frame basis?
All the background I'm provided with is that "Average bitrate is VBR implemented as a compromise between the two: the bitrate is allowed to vary for more consistent quality, but is controlled to remain near an average value chosen by the user, for predictable file sizes.". Is that enough to answer the question?
Answer: no