I threw a rough draft of an alternative format incorporating the comments received so far in this discussion on the wiki: http://wiki.xiph.org/index.php/OggPCM#Format Oliver, This seems to me like it would support the ambisonic requirements you mention, though it doesn't (and I imagine won't) describe the mic locations. Somebody who actually uses that info could probably define extra header pages for a later version of this spec. I hadn't even heard of ambisonics until your post, to be honest. John oliver oli wrote:> Erik de Castro Lopo wrote: > >> f) Encoding of channel information. In a two channel file, >> is the audio data a stereo image or two distinct mono >> channels? For a file with N (> 2) channels, are there pairs >> of channels which should be considered as a stereo >> pairs or do you want to place these stereo pairs as >> separate streams within a single ogg container? What >> about multi channel surround sound (there are a number >> of different formats like 5.1 and 7.1) or quadraphonic? How >> are you going to specify which channel is which. Being able to >> encode this stuff easily is **vital**. > > > please don't forget ambisonics :-) > > 2 channel UHJ > 4 channel 1st order > 9 channel 2nd order > 16 channel 3rd order > > etc. > _______________________________________________ > ogg-dev mailing list > ogg-dev@xiph.org > http://lists.xiph.org/mailman/listinfo/ogg-dev
John Koleszar wrote:> I hadn't even heard > of ambisonics until your post, to be honest.because people don't know how to distribute ambisonics. no way to play it in a DVD player. there are no easy to use software players that decode ambisonic files and there are no widely used audio file formats that support ambisonics (you can store 4 channel in many audio file formats, but it's not tagged as ambisonics). Apple's CAF is the only format I know of that supports ambisonics (4channel B-Format only).
On Thu, Nov 10, 2005 at 05:30:10PM +0100, oliver oli wrote:> John Koleszar wrote: > >I hadn't even heard > >of ambisonics until your post, to be honest. > > because people don't know how to distribute ambisonics. no way to play > it in a DVD player. there are no easy to use software players that > decode ambisonic files and there are no widely used audio file formats > that support ambisonics (you can store 4 channel in many audio file > formats, but it's not tagged as ambisonics). Apple's CAF is the only > format I know of that supports ambisonics (4channel B-Format only).That is a reason for us to proactivly support it. Especially if this is true: http://en.wikipedia.org/wiki/Ambisonics "The Ogg Vorbis project has shown interest in implementing ambisonics as a means for including surround sound in their project.">From the wiki, it seems to be only 4 channels, not more, even though you mayhave many more speakers. I don't know how this "WXYZ" data is setup, if XYZ are just other audio channels which can be handled the same way or if they need to be treated special.. Big question I have is: Is it patent-clear? Trademark-clear? There is a patent by Michael Gerzon on the tetrahedral array (soundfield) microphone, but which software patents exist for the system itself needs to be investigated further. -- The recognition of individual possibility, to allow each to be what she and he can be, rests inherently upon the availability of knowledge; The perpetuation of ignorance is the beginning of slavery. from "Die Gedanken Sind Frei": Free Software and the Struggle for Free Thought by Eben Moglen, General council of the Free Software Foundation