Opus: Can CUCM configure a minimum and maximum bitrate for Opus calls?

[Nadav]

Hi,

Opus can take anywhere between 5kbps and 0.5Mbps per call. However we have some low-bandwidth links and we'd like to ensure number of calls over these links, while also not hurting other application bandwidth. For example, capping a single opus call at 64kbps, 128kbps etc.

Is this something that's configurable for CUCM? Is it possible also for conference bridges and CMS?

Alternatively, is it possible to configure Opus as CBR with different bitrate depending on regions matrix?

Thanks.

[b.winter]

The max. or min. bitrate for OPUS cannot be configured.

With regions, you define, which max. bitrate a call between to devices can have, therefore limiting the possible negotiated codecs.

E.g when setting it to 16k, it will automatically filter all codecs, that have higher bitrates (like G711)

[Nadav]

Thanks,

Opus appears under the Audio Codec Preference List as 6k-510k. So if I configure inter-region max bitrate as 64k, would that mean Opus is picked first because 64 is between 6 and 510?  

[Roger Kallberg]

If you want Opus to be the preferred codec you’ll need to define it in the codec preference list that is used in conjunction with regions.

[b.winter]

As @Roger Kallberg wrote, if you want the OPUS get picked first, then you have to edit the order of the Codec preference list. The regions only define the max. bitrate a call can have, and therefore "filters" every codec, that has a higher bitrate.

[Jonathan Schulenberg]

Correct. You cannot define the minimum but the intra-/inter-region bandwidth defines the max for Opus.

Opus should be highly preferred by default in the Audio Codec Preference Lists; I would be surprised if you had to mess with that.

[Nadav]

Hi,

It is. But I also need to manage by bandwidth to a degree, I can't have a codec taking up to 510kbps for a voice call. 

Opus appears under the Audio Codec Preference List as 6k-510k. If I configure inter-region max bitrate as 64k, would that mean Opus is picked first in accordance with the ACPL because 64 is between 6 and 510?  

If so the only way to manage the bandwidth is hoping that the codec's VBR works as advertised once the queue gets congested.

[b.winter]

Hi,

It is. But I also need to manage by bandwidth to a degree, I can't have a codec taking up to 510kbps for a voice call. --> As already written, that's what regions are there for.

Opus appears under the Audio Codec Preference List as 6k-510k. If I configure inter-region max bitrate as 64k, would that mean Opus is picked first in accordance with the ACPL because 64 is between 6 and 510? --> Just because you set it at first order, it doesn't necessarily get picked first. Only the offer from CUCM's point of view will have the codec as first in it's list. The other system may not be supporting it or pick another one.

[Nadav]

Hi,

My use case is a single CUCM cluster with all endpoints supporting OPUS, so if Opus is highest on the ACPL and not limited by regions then it would be picked. From your response I take it that if I were to limit the region to 8 or 64kbps it could still pick Opus because of the range I mentioned earlier.

Regarding "As already written, that's what regions are there for" I suppose I was interested in knowing if I could use Opus VBR across the board and somehow count on it being flexible enough under various bandwidth restrictions whether in the LAN, broadband WAN or narrowband WAN. This is mostly to simply configurations in the CUCM. 

[Roger Kallberg]

If you have a need to set limits on the bandwidth used you’ll have to set that with region(s). Even if Opus has a VBR it would not AFAIK “negotiate” what bandwidth to use based on variable network conditions.