/*
 * Add support telephony event
 */
if (endpt->has_telephone_event)
{
    //DTMF 8kHz
    m->desc.fmt[m->desc.fmt_count++] =
        pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR);

    /* Add rtpmap. */
    attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr);
    attr->name = pj_str("rtpmap");
    attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR
                 " telephone-event/8000");
    m->attr[m->attr_count++] = attr;

    /* Add fmtp */
    attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr);
    attr->name = pj_str("fmtp");
    attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR " 0-15");
    m->attr[m->attr_count++] = attr;
}

    // Add rtpmap.
    attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr);
    attr->name = pj_str("rtpmap");
    attr->value = pj_str("97"
                 " telephone-event/16000");
    m->attr[m->attr_count++] = attr;

    // Add fmtp
    attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr);
    attr->name = pj_str("fmtp");
    attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR " 0-15");
    m->attr[m->attr_count++] = attr;

Hi all, I have found a 'hack' which seems to work, but I'd really like to know if it's advisable to do this, and if possible, if someone could suggest a better way. So firstly to elaborate on my need. I would like the SIP client to advertise, along with its codecs the telephone-event/8000 or telephone-event/16000 or both depending on the codecs being used. So overall, depending on the sampling rate of the codec being used, the RFC 2833 DTMF tones should be sent as either telephone-event/8000 or telephone-event/16000. I explored the code and I was surprised to find that the /8000 part was hardcoded. <endpoint.c> #if defined(PJMEDIA_RTP_PT_TELEPHONE_EVENTS) && PJMEDIA_RTP_PT_TELEPHONE_EVENTS != 0 /* * Add support telephony event */ if (endpt->has_telephone_event) { //DTMF 8kHz m->desc.fmt[m->desc.fmt_count++] = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR); /* Add rtpmap. */ attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr); attr->name = pj_str("rtpmap"); attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR " telephone-event/8000"); m->attr[m->attr_count++] = attr; /* Add fmtp */ attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr); attr->name = pj_str("fmtp"); attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR " 0-15"); m->attr[m->attr_count++] = attr; } #endif Can someone explain why this hard-coding? Is there never any need to change the sampling rate? <From RFC 2833> 4.4 Payload Format Based on the characteristics described above, this document defines an RTP payload format called "tone" that can represent tones consisting of one or more frequencies. (The corresponding MIME type is "audio/tone".) The default timestamp rate is 8,000 Hz, but other rates may be defined. Note that the timestamp rate does not affect the interpretation of the frequency, just the durations. So here's my hack in endpoint.c .. //DTMF 16kHz m->desc.fmt[m->desc.fmt_count++] = pj_str("97"); // Add rtpmap. attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr); attr->name = pj_str("rtpmap"); attr->value = pj_str("97" " telephone-event/16000"); m->attr[m->attr_count++] = attr; // Add fmtp attr = PJ_POOL_ZALLOC_T(pool, pjmedia_sdp_attr); attr->name = pj_str("fmtp"); attr->value = pj_str(PJMEDIA_RTP_PT_TELEPHONE_EVENTS_STR " 0-15"); m->attr[m->attr_count++] = attr; .. I know this is a silly and ugly hack. But it seemed to convince the remote side to let me send DTMF events to it. I found very scant information about this on the internet, so please forgive me if its a silly question. Regards, Arjun > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 3 Aug 2012 13:27:52 +0300 > From: Arjun Kamath <junnaonly@gmail.com> > To: pjsip@lists.pjsip.org > Subject: [pjsip] telephone-event/16000 > Message-ID: > < > CADzHbEUH7LPPgHeSTfVDw54BPZV2vuUoS5VLXjZfQZne4GJDdQ@mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Hi, > > Does PJSIP support sending DTMF tones as telephone-event/16000. Right now, > when I have AMR-NB active, DTMF works fine, but I get the > PJMEDIA_RTP_EREMNORFC2833 with AMR-WB. > > -- > Best Regards, > > Arjun P. Kamath > >