[opus] Opus for ASR

[Timothy B. Terriberry]

Young, Milan wrote:
> Is there any precedent for standard flags associated with a codec ( eg bit rate)?
> Any other good reasons for including aspects of encoding in 6716 or pushing through a sibling RFC?

It's too late for 6716 (unless done as an errata), but 6716 doesn't 
define an actual file format or mime type. That is currently done in 
draft-terriberry-oggopus 
(http://tools.ietf.org/html/draft-terriberry-oggopus, which will 
hopefully be promoted to a WG draft at some point). See Section 8. 
That's probably the right place to do something like this.

RFC 6381 defines a "codecs" parameter for mimetypes with a dot-separated 
namespace for adding additional codec-specific parameters. I'm not sure 
bitrate makes sense as part of a mimetype, but a codecs=opus.asr might 
be appropriate.

Don't be confused by the "profiles" parameter from RFC 6381, though. 
That's meant in the ISO/MPEG sense of something which defines what the 
decoder must support to decode a file. What you're interested in is 
controlling the encoder (I hope; we'd prefer not to have decoders that 
only support a subset of Opus's functionality because it's bad for 
interoperability).