[Asterisk-video] capability translation from h245 to SIP

[Dan Julius]

Hi, Sergio,

If there is no capability mapping, how does asterisk decide what
capabilities to put in the SDP body of the SIP Invite message?


When I originate a call from a Nokia N73 to a SIP client, the Invite message
includes and SDP section for video:

m=video 10070 RTP/AVP 34 103
a=rtpmap:103 h263-1998/90000
a=sendrecv


When I originate a call from a Nokia N95 the SDP is different and also
includes the h263/9000 capability:

m=video 10120 RTP/AVP 34 103
a=rtpmap:34 H263/90000
a=rtpmap:103 h263-1998/90000
a=sendrecv




Thanks,
Dan

On Tue, Sep 9, 2008 at 11:54 AM, Sergio Garcia Murillo <
sergio.garcia at fontventa.com> wrote:

>  Hi Dan,
>
> There is no capability negotiation, or mapping between SIP and the h245, I
> send fixed ones For H263 and AMR:
>
>
>           [0]={
>             capabilityTableEntryNumber = 1
>             capability = receiveAndTransmitVideoCapability
> h263VideoCapability {
>               qcifMPI = 2
>               maxBitRate = 520
>               unrestrictedVector = FALSE
>               arithmeticCoding = FALSE
>               advancedPrediction = FALSE
>               pbFrames = FALSE
>               temporalSpatialTradeOffCapability = FALSE
>               errorCompensation = FALSE
>             }
>           }
>           [1]={
>             capabilityTableEntryNumber = 2
>             capability = receiveAndTransmitAudioCapability
> genericAudioCapability {
>               capabilityIdentifier = standard 0.0.8.245.1.1.1
>               maxBitRate = 122
>               collapsing = 1 entries {
>                 [0]={
>                   parameterIdentifier = standard 0
>                   parameterValue = unsignedMin 1
>                 }
>               }
>             }
>           }
> .
>
> Best regards
> Sergio
>
> Dan Julius escribió:
>
> Hi,
>
> I'm experiencing some issues when using Asterisk as a gateway between 3G
> and SIP clients.
> I'm trying to complete a call using h263p as the video codec on the sip
> client in order to avoid  video transcoding.
> For audio I'm using AMR on the 3G side and g711 on the SIP side since most
> SIP clients don't support AMR out of the box.
>
> For some phones this works without a problem while other phones don't seem
> to show video depending on the SIP client.
> For example: N73 works with X-Lite, but not with OpenPhone. N95 works with
> both.
> I've traced this down to an issue with the capability exchange,
> specifically how capabilities are translated from h245 to SIP.
>
> Can someone point to which part of the code, Asterisk or libh324M does the
> mapping between capabilities?
> After reviewing some relevant RFCs and specs, it is not clear to me what
> the 1:1 mapping should be - is there any relevant documentation?
>
> Thanks,
> Dan
>
>
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>
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