[openal] OpenAL Soft 1.22.0 coming soon

[Chris Robinson]

On Monday, April 18, 2022 1:34:44 PM PDT Marc Lavallée wrote:
> Hi Chris,
> 
> What's could be missing in your proposal are references about UHJ (and
> SuperStereo).
> It would help for verification. In the article on Wikipedia, constants
> have less precision.

Hi.

The precision comes from starting with the encoding coefficients found on 
Wikipedia and Xiph.org, which have more precision for the S and D output:

<https://en.wikipedia.org/wiki/Ambisonic_UHJ_format#Encoding>
<https://wiki.xiph.org/Ambisonics#UHJ_format>

with one slight tweak from me. Changing the Y coefficient in the T output

T = j(-0.1432*W + 0.6512*X) - 0.7071*Y

to 0.7071068, since it clearly suggests (and other sources also indicate) this 
is supposed to be 1/sqrt(2). That encoder can then be reversed to get a 
decoder, with extra precision to more accurately restore what was given to the 
encoder. I suppose I could add a note about this.

For Super Stereo, there doesn't seem to be much readily available information 
other than 'it exists'. Wikipedia has a passing mention of decoders having a 
Super Stereo feature, in the section about undecoded UHJ having a "super 
stereo" effect (even though these are two separate things that happen to have 
the same name). The only other relevant and useful mention I've found is the 
site I linked in an earlier message:

<https://sursound.music.vt.narkive.com/xkMrL00t/what-is-super-stereo>

a (third party?) archive of the sursound mailing list, which provides some 
helpful information, but I don't think counts as an authoritative source.