On 23 Jul 2008, at 15:27, Benny Prijono wrote:
> On Wed, Jul 23, 2008 at 12:51 PM, Ruud Klaver <ruud at ag-projects.com>
> wrote:
> Hi,
>
> I'm trying to use the SDP negotiation part of pjmedia to process SDP
> related to MSRP (RFC 4975), but ran into some issues when it tried to
> complete the negotiation procedure. The process_m_answer function
> assumes that the formats in the m= line are integers and starts
> looking for rtpmap attributes, while for MSRP the formats aren't
> actually used and are set to a single "*".
>
>
> Actually it's not that bad, we have this in sdp_neg.c:618:
>
> /* Find matching answer */
> pt = pj_strtoul(fmt);
>
> if (pt < 96) {
> for (j=0; j<answer->desc.fmt_count; ++j) {
> if (pj_strcmp(fmt, &answer->desc.fmt[j])==0)
> break;
> }
>
> The idea is if pt is not a payload type number, pj_strtoul() should
> return 0 and the "if (pt<96)" checking above will be executed and it
> shouldn't need to check for rtpmap.
>
> But alas, there seems to be a bug in pj_strtoul(). Instead of
> stopping when it finds a non-digit character, it continues to treat
> the input as digit, causing it to return garbage value. I've just
> fixed this in the latest SVN.
>
Great, you dug deeper than me. :)
Indeed it was some assertion in that branch that failed on me. Thanks
for fixing it.
> Maybe there should be a check to see if the protocol field (called
> transport in pjsip) starts with RTP, as RFC 4566 states:
>
>
> I believe "proto" is shorthand for "transport protocol", so calling
> it transport is not too far off . :)
>
> If the <proto> sub-field is "RTP/AVP" or "RTP/SAVP" the <fmt>
> sub-fields contain RTP payload type numbers.
>
> But also:
>
> If the <proto> sub-field is "udp" the <fmt> sub-fields MUST
> reference a media type describing the format under the "audio",
> "video", "text", "application", or "message" top-level media
> types.
>
> ...
>
> For media using other transport protocols, the <fmt> field is
> protocol specific.
>
> But then the question is, how would pjmedia declare the negotiation to
> have succeeded?
>
>
> Currently, if both media type and transport protocol match, and
> there is matching format. That's probably good enough for MSRP.
>
> Cheers
> Benny
That works for me. Anything beyond that should be handled by the
application.
Ruud Klaver
AG Projects
