Hello Richard, > Having been caught up in beach bum matters for some years,
Happy to hear you are still providing the sharks with their daily ration of SCUBA divers... > I've lost track of all the latest machinations. But is there > a simple authoritative definition of AmbiX ? The best as far as I know is the one I pointed to before: <https://ambisonics.iem.at/xchange/fileformat/2011_nachbarzottersontacchideleflie_ambix.pdf/view> As a format definition it could be more concise, but all the required info is there. In summary: * The file format should be Apple's CAF, but in practice WAVEX is used (for the non-extended form of Ambix). * The file should contain all components for a given order, and thus have (N+1)^2 channels, unless the extended format is used (see below). * The channel order should be ACN, * Normalisation should be SN3D. Extended format: The file has a 'UUID chunk' [1] which contains an C * M matrix which transforms the available channels to a full set for a given order. C = number of channels in the file, M = (N+1)^2, with N = order. The exact format is in the paper. This can be used for several purposes: * Storing 'legacy formats' without modifying the sample data. The matrix converts to ACN/SN3D. * Horizontal only. The matrix provides the missing components (including those that are zero) assuming elevation = 0. * Subsets of full 3D that are sufficient to cover part of the sphere. The matrix transforms to the full set. That said, I have never encountered such a extended format file in the wild. [1] UUID chunks are possible in CAF only. They allow to extend the file format without breaking the spec and without requiring approval from Apple. Applications that do not know how to handle a particular UUID should just ignore the chunk. Ciao, -- FA _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound - unsubscribe here, edit account or options, view archives and so on.
