[Freeswitch-users] OPUS: Jitter Buffer for bridged calls to use FEC?

[Dragos Oancea]

That snip of documentation for JB is pretty old and obsolete I'd say, it
does not mention transcoding + FEC .
But where transcoding is used/needed is like a "point of termination".

Relevant docs (and best practices) about OPUS + JB + FEC here:
https://freeswitch.org/confluence/display/FREESWITCH/FreeSWITCH+And+The+Opus+Audio+Codec
If there's no JB then it can't be any FEC decoding.

If you just do OPUS->FS(bridge)->OPUS then no point of enabling the JB, it
only adds delay.

Cheers,
Dragos

On Tue, May 12, 2020 at 10:23 AM Alexander Haugg <Alexander.Haugg at c4b.de>
wrote:

> Hi,
>
>
>
> I try to find out the best practice to use the OPUS features.
>
> The scenario is:
>
>
>
> Client A -------> (JitterBuffer) FreeSwitch ----------------------->
> Client B
>
>                <---------------------- FreeSwitch (JitterBuffer) <--------
>
>
>
> Is this the correct way?
>
>
>
> In the documentation for OPUS the message is, JitterBuffer is needed to
> use FEC.
>
> But in the documentation for the JitterBuffer is written:
>
>               If both sides of a bridge are RTP and both sides have a jb,
> its fairly
>
>               useless.  In fact if anything, it can worsen call quality.
>
>
>
>               You should only run jitterbuffers at points of termination
> change of
>
>               protocol.  Examples, if FS was hosting a conference or IVR,
> if you are
>
>               bridging the call to a phone for instance, you want to not
> use a
>
>               jitterbuffer because you want to preserve the original
> timestamps so
>
>               your phone can use its own jitterbuffer.
>
>
>
>
>
> I think, package lost is the start indicator for FEC and normally the RTP
> sequence number is the indicator for package lost, but the sequence number
> is valid for the own SSRC space only.
>
> That means, if I have lost packages from Client A to Freeswitch is this
> information on the other side to client B missing, correct?
>
>
>
> Now the question, what is the best practice handle this scenario?
>
>
>
> Thanks a lot!
>
> Alex
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