Extended B format for Ambisonics interfacing

For first-order Ambisonics, the original B-format specification provides an intuitive and clear-cut definition of component sequence and normalization.  With higher-order Ambisonics there is no such clarity.  At least three different component sequences, four different normalizations and two different mixed-order schemes are competing for support.  We indicate the strengths and weaknesses of the key candidates, and make the case for supporting an extended B format as the no-metadata default.