[Freeswitch-users] proxy SDP

Fri Apr 15 18:05:14 MSD 2011

I'm really starting to think that no amount of documentation will ever
make this clear:

FreeSWITCH default media mode:
- RTP proxied by FreeSWITCH
- FreeSWITCH controls codec negotiation
- If endpoints agree on same codec, no transcoding is performed
- All features enabled - recording, DTMF interception, etc, etc

Proxy media mode:
- RTP proxied by FreeSWITCH (c= modified, that's it)
- FreeSWITCH has no control or even understanding of other SDP
parameters (pass through)
- Endpoints *MUST* agree on same codec because FreeSWITCH can't help them
- Virtually no features available

Bypass media mode:
- RTP *NOT* proxied by FreeSWITCH
- FreeSWITCH has no control over anything SDP related - it's
completely pass through from one leg to next (including c=)
- Endpoints must agree on same codec because FreeSWITCH doesn't even
see the media or SDP
- Virtually no features available

On Fri, Apr 15, 2011 at 5:48 AM, Sam <u2nsam at gmail.com> wrote:
> Hello,
>
> AS freeswitch modifies SDP ( Media Description & Media Attributes) so is
> there any way to just bypass that process.
>
> Regards
> Sam
>
>
> On Thu, Apr 14, 2011 at 6:32 PM, Steven Ayre <steveayre at gmail.com> wrote:
>>
>> I don't mean they're equivalent, because proxy_media has other sideaffects
>> such as disabling many features.
>>
>> I mean there are different better ways to avoid transcoding.
>>
>> What you suggested with bridge should indeed avoid it. Without the
>> absolute_codec_string the bleg would be offered all codecs supported by FS
>> which may be more than supported by the caller, however with that setting it
>> would only offer those supported by both the caller and FS. The callee will
>> pick one it supports (or return 488 Not Acceptable Here). The aleg will then
>> use the same codec as the bleg, so at that point both legs will be using the
>> same codec so no transcoding will take place (unless you try using something
>> like eavesdrop/record). You could then if you wanted handle the 488 Not
>> Acceptable Here by redialing without absolute_codec_string to try again,
>> this time the bleg could use a different codec than the aleg (transcoding).
>>
>> -Steve
>>
>>
>> On 14 April 2011 13:28, Sergey Okhapkin <sos at sokhapkin.dyndns.org> wrote:
>>>
>>> Do you mean
>>>
>>> set proxy_media=true
>>>
>>> is the equivalent of
>>>
>>> set late_negotiation=true
>>> bridge {absolute_codec_string=${ep_codec_string}}blah
>>>
>>> and transcoding will never happen?
>>>
>>> On Thursday 14 April 2011, Steven Ayre wrote:
>>> > Proxy media is not required for 2 NAT clients to talk to each other.
>>> >
>>> > Transcoding won't be used if both legs use the same codec, and you can
>>> > use
>>> > late-negotation/absolute_codec_string to encourage that.
>>> >
>>> > -Steve
>>> >
>>> > On 14 April 2011 11:22, Sergey Okhapkin <sos at sokhapkin.dyndns.org>
>>> > wrote:
>>> > > Proxy media is useful not for T38 only. It's a way for 2 NATed
>>> > > clients to
>>> > > communicate with each other if there are common codecs, no
>>> > > transcoding
>>> > > involved.
>>> > >
>>> > > On Thursday 14 April 2011, Steven Ayre wrote:
>>> > > > You misunderstand I think... it *isn't* needed for T38 any longer.
>>> > > > Only
>>> > >
>>> > > in
>>> > >
>>> > > > very old versions.
>>> > > >
>>> > > > -Steve
>>> > > >
>>> > > > On 13 April 2011 23:17, Madovsky <infos at madovsky.org> wrote:
>>> > > > > maybe change the param name to proxy_media_t38 ;)
>>> > > > >
>>> > > > > ----- Original Message -----
>>> > > > > From: "Kristian Kielhofner" <kris at kriskinc.com>
>>> > > > > To: "FreeSWITCH Users Help"
>>> > > > > <freeswitch-users at lists.freeswitch.org>
>>> > > > > Sent: Wednesday, April 13, 2011 2:10 PM
>>> > > > > Subject: Re: [Freeswitch-users] proxy SDP
>>> > > > >
>>> > > > >
>>> > > > > Brian,
>>> > > > >
>>> > > > >  For all of the confusion proxy media creates I still see cases
>>> > > > > where
>>> > > > >
>>> > > > > it is useful...  It shouldn't be removed completely.
>>> > > > >
>>> > > > > On Tue, Apr 12, 2011 at 8:55 PM, Brian West
>>> > > > > <brian at freeswitch.org>
>>> > >
>>> > > wrote:
>>> > > > > > We aren't a proxy... we have transcended into this quasi proxy
>>> > > > > > in
>>> > >
>>> > > some
>>> > >
>>> > > > > > scenarios which mostly involve t.38... as for proxy media DO
>>> > > > > > NOT
>>> > > > > > USE IT. Just saying it might go away since the purpose of it is
>>> > > > > > now not needed since we have full t.38.
>>> > > > > >
>>> > > > > > Thanks,
>>> > > > > > Brian
>>> > > > >
>>> > > > > --
>>> > > > > Kristian Kielhofner
>>> > > > >
>>> > > > > _______________________________________________
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>>> > >
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>>> > > > >
>>> > > > >
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>>
>>
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-- 
Kristian Kielhofner