Improve RTSP/RTP layer

Roadmap/checklist for Josh Allmann's Summer of Code Project:

• Primary goal: improve the receiver compatibility
  • Add support for more widespread formats ([list will follow check gst live555 and feng])
    • X-Qt/quicktime depacketizer (see X-QT patch)
      • Not implemented during GSoC, the old patch polished up and committed by Martin
    • SVQ3 [1] and QDM2 [2] depacketizers
      • Committed
    • VP8 (see https://groups.google.com/a/webmproject.org/group/webm-discuss/browse_thread/thread/550f946b0e22ead2# )
      • Committed
  • support Quicktime http tunnel mode
    • Initial implementation done and committed, not supported in the RTSP muxer yet, missing handling of the x-server-ip-address header
  • untangle the AAC and mpeg4 format specific code from rtsp.c, make them proper dynamic payload handlers
    • Committed
  • factorize out common code for parsing SDP (fmtp) lines, that is duplicated in parse_h264_sdp_line, amr_parse_sdp_line and xiph_parse_sdp_line
    • Committed
  • add RTP packetizers for codecs that we already have depacketizers for (Theora, Vorbis, SVQ3, QDM2, any other? - VP8, in parallel with the depacketizer for that)
    • Xiph and VP8 packetizers committed
  • Real RTSP-HTTP, with port knocking
  • support RTCP/Bye as end-of-file (see small task)
    • Committed
• Secondary goal: improve application integration
  • Provide an API to expose the rtcp layer (and the equivalent in RDT dialect)
  • Try to support subtitle streams (either as rtcp-xr or application/text stream)
  • Make VideoLanClient, MPlayer or Xine use FFmpeg RTSP
    • Patch submitted to VLC, awaiting review
  • Implement protocol variations (e.g. DCCP or improve SCTP)
  • Untangle MPEG2-TS/RTP from rtpdec into a dynamic payload handler. Write a packetizer first, unless we find such a server to test against.
  • Reduce ffrtsp startup time
  • Small Xiph RTP optimization: avoid the extra memcpy to packet; instead, hook av_init_packet up to url_close_dyn_buf
    • Committed

Mentor: Luca Barbato, Martin Storsjö, Ronald S. Bultje