[Freeswitch-users] To Proxy Media or Not

[Steven Ayre]

Yes.

You said you have PCMU and G729 enabled? Is that both inbound and outbound?

If so, it means that either your caller negotiated PCMU with FS, then FS
offers PCMU+G729 to the callee and they pick G729, or visa versa.

That's because FS will offer all the enabled codecs on the bleg. That leaves
the choice up to the callee on what they use and it might not be the same as
the aleg. That's only a problem with passthrough codecs such as G729, or if
you want to avoid transcoding because of CPU.

The way around it is to set either disable-transcoding or late-negotiation
parameters on the SIP profile.
disable-transcoding will only offer on the bleg the codec which has already
been negotiated for the aleg.
late-negotiation approaches it from the other end - it doesn't pick an aleg
codec straight away but instead offers all the choices to the bleg and then
uses for the aleg what the bleg selected.

-Steve



On 9 March 2011 19:21, Max Clark <max.clark at gmail.com> wrote:

> So this is an interesting side effect of removing proxy_media=true
> from the dialplan:
>
> 2011-03-09 19:17:31.055236 [ERR] mod_g729.c:145 This codec is only
> usable in passthrough mode!
> 2011-03-09 19:17:31.055236 [ERR] switch_core_io.c:897 Codec G.729 decoder
> error!
>
> Am I reading this correctly that FreeSWITCH attempted to transcode a
> G.729 audio stream?
>
> On Wed, Mar 9, 2011 at 11:07 AM, Kristian Kielhofner <kris at kriskinc.com>
> wrote:
> > Fax over g711 (if it's going to work at all) should not be affected by
> > proxy media or default media handling as long as you allow PCMU/PCMA
> > when using the default media handling.  However, T38 and fax over 711
> > are completely different.  Using T38 through FreeSWITCH with the
> > default media handling will require some extra configuration (nothing
> > drastic).
> >
> > No one said anything about transcoding...  Proxy media mode does not
> > have the ability to transcode at all as FreeSWITCH is completely
> > unaware what codec you are using (internally it actually reports
> > "proxy" as the codec).
> >
> > Just because you're using default media mode DOES NOT mean you will be
> > transcoding.  Using some Sofia params and late-negotiation dialplan
> > logic you can have an incredible amount of control over what codecs
> > your end points are using.  As long as they agree on at least one
> > codec and codec parameters you are the one who decides which codecs
> > take precedence and whether or not you'll be transcoding.
> >
> > On Wed, Mar 9, 2011 at 12:13 PM, Max Clark <max.clark at gmail.com> wrote:
> >> Advantages of Proxy Media:
> >>
> >> 1) Support codecs not natively supported by FreeSWITCH
> >> 2) Lower CPU resources on FreeSWITCH
> >>
> >> So for 1) I'm really only concerned with t38/fax over g711. With our
> >> current configuration faxing (although unsupported) is working just
> >> fine. What should I expect if I revert to media mode?
> >>
> >> 2) If I disable transcoding, what kind of difference in resource
> >> utilization should I expect? Nominal (less than 10%), Moderate
> >> (11-30%), or more?
> >>
> >> Thanks,
> >> Max
> >>
> >
> > --
> > Kristian Kielhofner
> >
>
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