Re: [codec] WG Review: Internet Wideband Audio Codec (codec)

["Christian Hoene" <[e-mail]>]

> This codec should be also useful in
> conference
> scenarios, where you have to decode it at conference server and encode
> mixed signal again. And if I haven't missed something, this use-case
> was
> explicitly listed in codec requirements.

The conferencing scenario is not yet well described in the current codec requirements document. Different kinds of systems are possible:

1) A central conferencing server that serves all clients.
- a) which does a efficient single changing mixing - still a challenge if you have multiple operational modes in a codec.
- b) which does a more intelligent mixing using (at least) two channels to support spatial hearing - this increases the quality of conference call significant. Thus, stereo modes must be supported if the codec shall support state of the art conferencing technologies.
2) A mesh-like N-to-N transmission conference call. Then you might benefit from layered coding because you have at a client you have to encode only once. But then again, how to support multiple coding modes?
3) One client acts as conference server (similar to 1)

In total, the support of conferencing calls will require:
- Layered coding
- Efficient mixing of streams
- Support of stereo
- Good (self-)transcoding
Is this all achievable?

Christian