[opus] comment writing in opus / liboggz

[Ian Malone]

It seems there still isn't a tool (at least not a Xiph one) for
modifying Opus comments from the command line. I've had a go at adding
support in liboggz (which is fairly trivial, since it just means
adding recognition for the Opus stream).

That certainly works for comment editing, but I'm not sure if it's is
good enough to commit back, because timing gets reported back slightly
out, due to the Opus pre-seek, I think. Fixing that probably requires
adding an Opus-specific metric to liboggz, since the current default
linear one doesn't deal with first granule position being set. Thought
I'd check before getting into that whether anyone has looked at this
already?

(I also suspect the way liboggz handles pre-roll may need to be
extended, since it seems to be working in packet count, like Vorbis,
rather than sample count as Opus does.)

Another thought, could vorbiscomment do with having Opus comment support added?

-- 
imalone
http://ibmalone.blogspot.co.uk