[Freeswitch-users] FS6947 - Tuning Opus bandwidth

Julien Chavanton jchavanton at gmail.com
Sun May 31 14:09:48 MSD 2015


Hi Emrah,

The settings exist but they are not available from the dialplan, right now
they can only be set globally .
https://freeswitch.org/confluence/display/FREESWITCH/mod_opus

You can control the bandwidth using maxplaybackrate and maxplaybackrate
this will control the local encoder and also adds the corresponding FMTP
parameters to the SDP to be used by the remote encoder (if it does
implement the following draft, the draft is evolving but I think it as not
changed)

https://tools.ietf.org/html/draft-ietf-payload-rtp-opus-11

Maybe something like :

maxaveragebitrate 24000
maxplaybackrate 8000

The discussion was getting slightly more complicated when we where
discussing about unnecessary resampling this was not a problem but it was
just adding extra load on the server.

On Sun, May 31, 2015 at 6:09 AM, Emrah <lists at kavun.ch> wrote:

> Hi list,
>
> I re-read FS6947 and don't understand how this problematic was addressed
> and the issue fixed.
> The scope is simple. There should be a setting in the dialplan that allows
> downsampling of Opus for applications that do not require the 48khz / 2
> channels framework. I.e.: terminating to the PSTN with Opus to take
> advantage of low bandwidth and great PLC.
> There seems to be a lot of confusion around bandwidth in general there. It
> doesn't matter if the internal clock of the device is always sampling at
> 48khz / 2ch. There are settings that can facilitate a lower bandwidth
> consumption for particular use cases, and it seems the reason it is not
> being implemented in FS is just a matter of being confused about the intent
> of the 48khz 2ch base.
> Please revisit this issue. FS should allow tuning of Opus audio / network
> bandwidth in the dialplan. It would optimize greatly lots of use cases.
> If I'm calling the PSTN, I'd rather have my client downsample and stream
> at a lower bandwidth, even if my audio capture would still be at 48khz /
> 2ch as per the RFC, and save on bandwidth, than transcode the full 48khz
> spectrum into PCM on my FS and minimize processing power on the client's
> side.
>
> Jira here: https://freeswitch.org/jira/browse/FS-6947
>
> Emrah
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