[opus] Opus now supported at Magnatune

[John Buckman]

> 64 kbps Opus is transparent for many samples with cheap headphones.
> 128 kbps Opus is transparent for almost any sample with good headphones.
> 
> I'd probably use 192 kbps Opus for 'very high quality' and the default
> (96 kbps for coupled stereo) for 'high quality'.

Thanks for those suggestions.

> Do you plan to offer opus versions as individual songs for download or
> playlist use?

Yes, though currently I default to OGG when supported, and will move to using OPUS when it's supported, as the audio quality is even a bit better.  

Getting ZIP files of all our albums, with the right metadata, was a good 1st step, and a good way to debug whatever problems might arise (ie, my doing the metadata tagging incorrectly).

As to playlists -- the way it'll work is that the "most open" audio format you support will be used by default, in this order: opus, ogg, mp3.

-john