[codec] draft-spittka-payload-rtp-opus-00: a=fmtp:101 application=audio

[Lars Immisch <[e-mail]>]

Hi,

I have integrated the Opus codec into a SIP UA (based on pjsip). The intended application is for a broadcast (podcast) studio: a guest calls into the studio, talks (and maybe even sings) with the host, and the conversation is broadcast.

For this application, the highest available quality is desirable. 

I have experimented with Opus in the appliation=audio setting and am pretty happy with it. But reading draft-spittka-payload-rtp-opus-00, I find no provision to encourage the other party to send an Opus stream encoded with the "audio" application setting.

I'd like to propose an additional "application" parameter that can take the value "audio", "lowdelay" (and maybe "voip"):

In my example, the studio would offer (or answer with):

  m=audio 54312 RTP/AVP 101
  a=rtpmap:101 opus/48000
  a=fmtp:101 application=audio

This would prompt the encoder on the other side to use the audio application mode of Opus.

I hope this makes sense. If it does, I'd be very pleased if it could be included in the next draft. 

- Lars Immisch