Frame Priority Marking RTP Header Extension
draft-even-avtcore-priority-markings-02

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AVTCore                                                          R. Even
Internet-Draft                                                   O. Idan
Intended status: Standards Track                     Huawei Technologies
Expires: December 26, 2018                                 June 24, 2018

              Frame Priority Marking RTP Header Extension
              draft-even-avtcore-priority-markings-02.txt

Abstract

   This document updates the Frame Marking RTP header extension in
   draft-ietf-avtext-framemarking-06 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
   discardable frames

Status of This Memo

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   This Internet-Draft will expire on December 26, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://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 . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   4
   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.  An encoder may want to mark
   multiple frames as discardable but with different drop priority,
   allowing the middle box to discard part or all the discardable
   frames.  The middle box can use the priority information for deciding
   which frames to drop.  By monitoring the RTP stream and the frame
   marking a middle box can estimate how many RTP packets are in each
   priority and use this information for the dropping decision.

   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

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      B1 is dropped then B2 can be dropped too.  By using priority B1
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