Frame Priority Marking RTP Header Extension
draft-even-avtcore-priority-markings-00

AVTCore                                                          R. Even
Internet-Draft                                                   O. Idan
Intended status: Standards Track                     Huawei Technologies
Expires: February 28, 2018                               August 27, 2017

              Frame Priority Marking RTP Header Extension
              draft-even-avtcore-priority-markings-00.txt

Abstract

   This document updates the Frame Marking RTP header extension in
   draft-ietf-avtext-framemarking-14 used to convey information about
   video frames that is critical for error recovery and packet
   forwarding in RTP middle-boxes or network nodes.  The flags for frame
   marking for non-scalable streams include the D bit to mark a frame
   that can be discarded, and still provide a decodable media stream.
   There is also the I bit for frames that can be decoded independent of
   prior frames, e.g. intra-frame.

   This memo adds priority values for the non-scalable streams droppable
   frames

Status of This Memo

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   This Internet-Draft will expire on February 28, 2018.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of

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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Frame Priority  . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   3
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   Frame Marking RTP Header Extension [I-D.ietf-avtext-framemarking]
   provides a single bit for marking frames that may be discarded by a
   middle box for non-scalable streams.  Having one bit for marking a
   discardable frame provides the same information to a middle box that
   need to drop few frames or many frames.  If the encoder wants to mark
   multiple frames as droppable allowing the middle box to discard part
   or all the discardable frames.  The middle box can use more
   information for deciding which frames to drop.  A video stream is
   composed of Group of Pictures (GOP) where the GOP includes I,P and B
   frames.  A GOP is typically bound by I frames and is 15-30,60 frames
   long but can vary with frame rate, content complexity and encoder
   implementation.  There are a couple of use cases that can benefit if
   discard priority is available.

   o  When there are contiguous non referenced B frames dropping all of
      them will reduce the actual frame rate.  By providing different
      priority to each of these B frames the middle box can affect the
      actual frame rate.  This information can be also deducted based on
      the number of contiguous frames but having priority will make it
      easier for the middle box for example when the frames are
      interleaved.

   o  When there are referenced B frames, for example a non referenced B
      frame (B1) followed by a B frame (B2) referenced by B1 only.  If
      B1 is dropped then B2 can be dropped too.  By using priority B1
      can have lower priority than B2.

   o  Dropping a P frame that is close to the end of the GOP is also
      possible comparing to a P frame in the beginning of the GOP.  The

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      encoder can know when such P frame exist and mark is as droppable
      with lowest priority.

2.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Frame Priority

   This memo adds two P bits to the RTP header extension defined in
   [I-D.ietf-avtext-framemarking] section 3.1.

   RTP Header Extension for non-scalable streams:

      0                   1
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  ID=? |  L=0  |S|E|I|D|P P 0 0|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   P: Priority bits (2 bits).  If the D bit is set to zero these bits
   MUST be zero.  If the D bit is set to 1 the values 00 is the highest
   drop priority (this will be the case when priority is not specified)
   and 11 is the lowest drop priority.

   Based on the use cases from the introduction, the priority of the non
   referenced B frame will be 00, the priority of the referenced B
   frames will be 01 and the priority of the droppable P frame will be
   10.  If the middle box drops the frames marked with priority 00 it
   can now drop the frames marked with priority 01 since they are not
   needed for decoding the stream.

4.  IANA Considerations

   There are no IANA actions

5.  Security considerations

   This memo does not add any security information to the ones in
   [I-D.ietf-avtext-framemarking]

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6.  Normative References

   [I-D.ietf-avtext-framemarking]
              Berger, E., Nandakumar, S., and M. Zanaty, "Frame Marking
              RTP Header Extension", draft-ietf-avtext-framemarking-05
              (work in progress), July 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
              editor.org/info/rfc2119>.

Authors' Addresses

   Roni Even
   Huawei Technologies
   Tel Aviv
   Israel

   Email: Roni.even@huawei.com

   Ofer Idan
   Huawei Technologies
   Hod Hasharon
   Israel

   Email: ofer.idan@huawei.com

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