On Fri, Aug 14, 2009 at 05:44:21PM -0400, David Robillard wrote: > > http://ambisonics.ch/standards/channels/ > > Excellent, thanks!
That is also the one I'd support, together with either n3d or n3d normalisation, but I wish I could share Joern's optimism about it being accepted... The matter came up in last year's AMB meeting in Graz. That was followed by some very hot and mostly useless discussion on the surround sound list and at various other shady ad-hoc places. It was scheduled to be discussed again at this year's meeting in Graz where both Joern and I were present along with the complete beau monde of Ambisonics, But no conclusion was arrived at, first because we didn't have enouth time and second because for many of the participants it was something they were not prepared for - the necessary introductory talk took almost all the time we had. > > most favoured normalization scheme is sn3d, i.e. plugins will have to > > deal with inputs greater than 1.0f. Not really - for n3d some of the _panning gains_ can be > 1 iff you set W = 1. Absolute levels are not the same thing as relative gains. For sn3d the panning gains are <= 1. > > but for political reasons, new plugins should use acn rather than fuma, > > so that's what should be defined as a standard first. if there is > > sufficient pressure and people are volunteering, another fuma scheme can > > always be added. > > Sounds good to me. Again I would 100% support that, but it is not current practice. Any application that uses this scheme will be the brave one that starts a revolution. > (Fons, what is the situation WRT this stuff with your ambisonics > plugins? AFAIK they are the only ones that exist in LAD land) The plugin set (did you get the latest and greatest ?) uses FuMa and also it assumes that positive azimuth is to the right which is plain wrong. The only reason for that is that most hosts can't create a widget that has negative values to the right and positive ones to the left (and LADSPA can't tell them they should do it). The plugins will remain what they are, but my support for FuMa ends there. All new stuff will be n3d or sn3d and use either the 'computer graphics' (= ACN) or 'Gerzon' order. If the new stuff is more than a plugin it could *maybe* offer FuMA as an option at the external interfaces, as e.g. AmbDec does. Internally everything will be n3d. Anyway, if ports are labeled in 'machine readable' way the order doesn't matter - a host will be able to sort things out. It does matter e.g. in a file format that doesn't have metadata to describe the order. Dave, don't worry about the weird order of the single character names shown on the web page about ACN, They are mentioned only to show how the order relates to the FuMa one. ACN doesn't use these names, it only uses the numbers. Another outcome of the Graz meetings is that the port groups that are currently named H#V# should really be named H#P#. The H#V# ones do also exist, but are different. I'll have to rename all existing AmbDec presets for the same reason. Ciao, -- FA Io lo dico sempre: l'Italia è troppo stretta e lunga. _______________________________________________ Linux-audio-dev mailing list [email protected] http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
