1. 03 Jan, 2014 1 commit
    • Julien Isorce's avatar
      rtpmanager: add new rtprtxsend / rtprtxreceive elements · 5a1aa759
      Julien Isorce authored
      The purpose of the sender RTX object is to keep a history
      of RTP packets up to a configurable limit (in time). It will
      listen for custom retransmission events from downstream. When
      it receives a request for retransmission, it will look up the
      requested seqnum in its list of stored packets. If the packet
      is available, it will create a RTX packet according to RFC 4588
      and send this as an auxiliary stream.
      
      The receiver will listen to the custom retransmission events
      from the downstream jitterbuffer and will remember the SSRC1
      of the stream and seqnum that was requested. When it sees a
      packet with one of the stored seqnum, it associates the SSRC2
      of the stream with the SSRC1 of the master stream. From then
      on it knows that SSRC2 is the retransmission stream of SSRC1.
      This algorithm is stated in RFC 4588. For this algorithm to
      work, RFC4588 also states that no two pending retransmission
      requests can exist for the same seqnum and different SSRCs or
      else it would be impossible to associate the retransmission with
      the original requester SSRC.
      When the RTX receiver has associated the retransmission packets,
      it can depayload and forward them to the source pad of the element.
      
      RTX is SSRC-multiplexed
      
      Fixes https://bugzilla.gnome.org/show_bug.cgi?id=711084
      5a1aa759