Hi again, thank you very much for the clarification. I find it very helpfull to think of Spats channel convention as ACN with a -90 degree rotation. It is quite easy to handle.
So far so good … so sorry for continuing the discussion anyway.
As for the discussion of how to categorise Spats channel layout :
You may argue that in terms of channel nomenclature there is no Spat channel format per se as it pertains to ACN. Adding a different convention to an existing format in terms of its spatial functionality would in my opinion suffice for treating it like a proper format (Spat-ACN, for instance). I don’t think you can put nomenclature over functionality as the two goes hand in hand. At least for me in actual practice.
As for the question if channel swapping could do the trick :
It is true that channel swapping should also be followed by a polarity change on the Y-axis to complete the operation. Krohnlachners Ambix-converter plugin actually includes sign-flipping (next to channel swapping), thereby collecting everything in one tool applicable upto 7th order. In practice I find that very convenient (and first and foremost safe).
The patch of Thibaut very clearly (and elegantly) shows the difference. I have added another patch to check how the same result can be achieved by channel swapping and polarity flipping (FOA only) using Spat5 objects. Just to see whether one or the other solution would have any benefits - either in terms of calculation or ease of operation - or if simply comes down to taste and/or habits. Your choice.
Best Hans Peter
Spat5-formats-[etude].maxpat (28.0 KB)