Re: [Linphone-developers] Outgoing call issue in iOS application in Linphne

[Elisa Nectoux]

Hi Vivek,

Thank you for your interest in Linphone.

However, it is not correct to say that Linphone is missing the a=rtpmap attributes for pcmu and pcma, as these attributes are not mandatory.

Please refer to RFC3264 [https://tools.ietf.org/html/rfc3264] An Offer/Answer Model Session Description Protocol, in section 5 "Generating the answer":

In the case of RTP streams, all media descriptions SHOULD contain "a=rtpmap" mappings from RTP payload types to encodings.  If there is no "a=rtpmap", the default payload type mapping, as defined by the current profile in use (for example, RFC 1890 [5]) is to be used.

RFC1890 has been replaced by RFC3551 but still defines PCMU and PCMA with static payload type numbers 0 and 8.

Equipments that require rtpmap for static payload types are hence non-conformant with RFC3264.

In order to workaround this non-conformance, linphone has a build-time option to request rtpmap to be always used in SDP. Just pass -DENABLE_RTP_MAP_ALWAYS_IN_SDP=ON to the cmake command line (or prepare.py).

For your information, the reason why we decided many years ago not to honor the "SHOULD" for static payload types is simply to save bytes in the INVITE or 200 Ok length by removing redundant information. Indeed, there are still many use case where MTU limit is major problem, for example when interoperating with SIP gateways that only support SIP/UDP transport.

Best regards,

Elisa Nectoux
Sales & Marketing

+33 (0)9 52 63 65 05
address@hidden

Belledonne Communications, the company behind the Linphone project

https://www.linphone.org

Le 8 août 2019 à 12:21, Vivek Tilva via Linphone-developers <address@hidden> a écrit :

Hello,

We are facing issue in outgoing calls , calls were not able to go through our provider which we are using , here is reply from our provider , it is related to codec , can you please help us.

Reply from Our provider:

" I checked the samples you have provided and I could observe few things in the calls which have failed.
The main reason for calls failing is because of the mismatch in codec negotiation.
Plivo accepts the call only on PCMU 0 and 8 ( g711).
The calling agent is sending an invite with the codec's 97 98 99 100 0 8 101.
But is missing to send the media attribute description for either 0 or 8, since the codec is not described our servers are rejecting the call.
To fix the issue you will have to send at least one of the codecs in the media attributes only then the calls will be processed"

It there any thing we can change in code to overcome this issue ?

--

Regards,

Vivek Tilva

Application Developer,
US +18572563703 | IN +91 9265391756

CallHippo.

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