= Integrating Third Party Media Stack with PJSIP =

== Introduction ==

PJSIP consists of several libraries which mostly are independent from one another. The library architecture diagram below shows how libraries are interacting with each other.



== SIP and Media Interaction ==

Pseudo-code when creating a call (same flow for caller and callee):

'''create_call()'''[[BR]]
{[[BR]]
    ''// Create the dialog''[[BR]]
    '''dlg = pjsip_dlg_create_uac/uas();'''

    ''// Create media transport (pair of RTP/RTCP socket) for''[[BR]]
    ''// transmitting/receiving the media from remote endpoint''[[BR]]
    '''media_transport = pjmedia_transport_udp_create();'''

    ''// Get the socket address info of the media transport''[[BR]]
    ''// These are needed to create a complete SDP descriptor''[[BR]]
    '''media_sock_info = pjmedia_transport_get_info(media_transport);'''
   
    ''// Create local SDP to be given to invite session''[[BR]]
    '''sdp = pjmedia_endpt_create_sdp(media_sock_info);'''

    ''// Create the invite session, giving it both the dialog''[[BR]]
    ''// and local SDP to be negotiated''[[BR]]
    '''inv = pjsip_inv_create_uac/uas();'''[[BR]]
}

'''pjsip_endpt_create_sdp(media_sock_info)'''[[BR]]
{[[BR]]
  ''// Query list of codecs that we support''[[BR]]
  '''codec_list[] = pjmedia_codec_mgr_enum_codecs();'''

  ''// Put each codec information in the SDP''[[BR]]
  ...

  ''// Put media socket address info in SDP c= and m= line''[[BR]]
  ...

  '''return sdp;'''
}