[opus] Opus now supported at Magnatune

[Timothy B. Terriberry]

John Buckman wrote:
> Magnatune.com <http://Magnatune.com>'s entire catalog is now
> downloadable in Opus format, with full metadata (small and large cover
> art) at 128k stereo.

As a long-time fan of Magnatune and what you're trying to do, this is 
pretty awesome.

> 1) I'm really impressed by your metadata implementation. It's very
> cleanly done, and the multiple artwork idea is fantastic.  One

Credit here mostly goes to Vorbis and FLAC. We just copied Vorbis's tag 
format and added a few features from FLAC's tools.

> suggestion: I couldn't find an example in the man pages or online of
> including album art in an .opus file, which would have been helpful.

You're right... if you run opusenc with no arguments, there's a detailed 
description of the --picture argument, but not in the man page. We'll 
fix that.

> 2) on the metadata topic, it'd be great if multiple Genre commands were
> allowed.  No other format has enabled this, but much music spans
> multiple genres, ether with a main-genre/subgenre split, or literally
> across two genres.  Ie: "Latin Music/Tango" or "Classical/Baroque"

If you pass --genre multiple times, it will actually encode multiple 
GENRE tags in the file. Not sure how many players will properly handle 
such a thing, though (my prediction: not many, though I think VLC will 
concatenate them into a comma-separated list).

> 4) In case you don't know Magnatune, we're an open-source friendly music
> collection, DRM free, offering unlimited downloading for members in
> various formats (mp3/wav/alac/flac/ogg/opus), with Creative Commons
> licensing applied to members' files as well.  Linux users account for
> 29% of our daily traffic.

My mother has been using your music for her photography slide shows for 
years, explicitly because of the CC licensing :).

> I'd be happy to provide audio files to the project under CC terms, if
> they could help you demo/show off the quality of your work.

"Paper Lights" from <http://magnatune.com/artists/albums/ehren-lines/> 
has been prominently featured at <http://www.opus-codec.org/examples/> 
and articles like 
<https://hacks.mozilla.org/2012/07/firefox-beta-15-supports-the-new-opus-audio-format/>, 
etc. Sadly, when I "Click to play a song" on the Magnatune page, though, 
it tries to use Flash (which I don't have installed).