Re: [WavPack-devel] Ambisonics support

[David B. <da...@wa...>]

Hello Oliver,

I am familiar with Ambisonics and actually had a lengthy e-mail exchange 
with Martin Leese on this about 18 months ago. At that time what made 
the most sense was to simply use the existing facility in WavPack that 
stores the RIFF header that exists on the .amb files (that are really 
WAV files). It is easy for a player that is Ambisonics-aware to read 
this information from the WavPack library as easy as it can read it from 
a .amb file. We also verified that existing .amb files were losslessly 
compressed with the existing version of WavPack (including all the 
Ambisonics info).

Perhaps this is sufficient. If not, I have been thinking of another 
feature that I could add to WavPack to support "custom" applications 
like Ambisonics. Basically, this would be to reserve a metadata ID 
whereby custom information could be stored in WavPack files. It would be 
up to the application using the metadata to define the format of the 
data block; the WavPack library would simply provide the APIs to write 
the data on encoding and read it when opening the files for decoding.

Or did you have something else in mind?

Thanks and regards,
David


Oliver Oli wrote:
> Hallo David,
> 
> is there any interest in adding support for Ambisonics?
> 
> It would require adding some metadata:
> 
> 1) A flag for Ambisonics
> 2) horizontal order (1 to 127)*
> 3) vertical order (0 to 14)*
> 4) optionally a flag indicating the channel gains (3 options: N3D,
> SN3D, peak normalized)
> 
> * these are max orders you can put in 255 channels.
> 
> I cannot provide any patch, I'm not a C programmer.
> 
> 
> If you are not familiar with Ambisonics: It's a surround format, that
> is independent from the speaker layout and also encodes height in only
> 4 channels. For playback you need an Ambisonics decoder, so it's
> important to tag an Ambisonics file properly, which would enable audio
> players to decode it without any intervention from the user (of course
> the player needs to support Ambisonics). You can also use more
> channels for improving the spatial resolution. 4 channels is 1st
> order, 9 channels is 2nd order, 16 channels is 3rd order Ambisonics,
> etc... See also
> 
> http://wiki.xiph.org/index.php/Ambisonics
> http://www.wikipedia.org/wiki/Ambisonics
> 
> 
> Oliver
> 
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