Conference bridge: Questions regarding no transcoding

[Nadav]

Hello,

I have an ISR 4k conference bridge which is used in the enterprise. No CUBE is necessary, nor would I like to use transcoding.

I have phones which support Opus, and I have some which don't.

1) If I were to have an Opus ad-hoc/meetme conference which was negotiated as Opus, and then an older phone wished to join which doesn't support Opus (but does support G.729 for example), could the conference then fallback to G.729 without disconnecting participants? 

Here is an example, O1 O2 and O3 are Opus-enabled and X1 doesn't support Opus:

a) O1 calls O2

b) O1 calls O3 and creates an ad-hoc conference

c) O2 adds X1 to the conference

2) I would also like to hear if the opposite is possible, namely changing the codec the moment all participants support it. For example:

a) X1 calls O1. Call is G.729

b) X1 calls O2 and creates an ad-hoc conference. Conference would be G.729 since X1 doesn't support Opus.

c) X1 adds O3, the conference is still G.729

d) X1 leaves conference, all participants are now Opus-enabled so the conference would now be encoded as Opus.

3) If these options are not possible, is Opus considered a high-complexity algorithm? I'd like to see what kind of hit it would be for my conference resources. 

Thanks for your time!

[Roger Kallberg]

As this and your other previous questions around Opus are quite specific to your individual setup I would recommend you to set it up and try it out as it is very unlikely that someone else has done the exact same things as you want to achieve.

[Elliot Dierksen]

This presentation from Cisco Live does not list Opus as a supported codec for the PVDM4 modules in ISR 4K routers. See page 55 for a list of supported codecs.

https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2019/pdf/PSOCOL-2009.pdf 

[Roger Kallberg · Accepted solution]

Your absolutely correct @Elliot Dierksen Opus isn't even on the list of supported codecs.

For a CFB DSP profile

selurt-voip-02(config-dspfarm-profile)#codec ?
  g711alaw  G.711 A Law 64000 bps
  g711ulaw  G.711 u Law 64000 bps
  g722-64   G722r64
  g729abr8  G.729ab 8000 bps
  g729ar8   G.729a 8000 bps
  g729br8   G.729b 8000 bps
  g729r8    G.729 8000 bps
  ilbc      ILBC codec

For a Xcoder DSP profile

selurt-cube-03(config-dspfarm-profile)#codec ?
  g711alaw      G.711 A Law 64000 bps
  g711ulaw      G.711 u Law 64000 bps
  g722-64       G722r64
  g729abr8      G.729ab 8000 bps
  g729ar8       G.729a 8000 bps
  g729br8       G.729b 8000 bps
  g729r8        G.729 8000 bps
  gsmamr-nb     GSMAMR NB codec
  ilbc          ILBC codec
  isac          ISAC codec
  pass-through  Stream Pass Through

[Nadav]

Interesting, I've read that since 17.6.1 it was supported for transcoding to other codecs. Here is one post on the matter:

https://community.cisco.com/t5/collaboration-voice-and-video/opus-codec-transcoding-with-pvdm4-amp-nim-pvdm-voice-dsp-module/ba-p/4465241 

I suppose that means that Xcoding is only for CUBE functionality and not conferencing. Thanks!

[Roger Kallberg]

As the article states that's specific to 17.6.1 and on-wards. As that not a MD release we're not even close to be on that yet. My output was from a gateway running 17.3.4a as that is the current MD release on the 17 release train.