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Idan 4 Intended status: Standards Track Huawei Technologies 5 Expires: June 26, 2019 December 23, 2018 7 Frame Priority Marking RTP Header Extension 8 draft-even-avtcore-priority-markings-03.txt 10 Abstract 12 This document updates the Frame Marking RTP header extension in 13 draft-ietf-avtext-framemarking-06 used to convey information about 14 video frames that is critical for error recovery and packet 15 forwarding in RTP middle-boxes or network nodes. The flags for frame 16 marking for non-scalable streams include the D bit to mark a frame 17 that can be discarded, and still provide a decodable media stream. 18 There is also the I bit for frames that can be decoded independent of 19 prior frames, e.g. intra-frame. 21 This memo adds priority values for the non-scalable streams 22 discardable frames 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on June 26, 2019. 41 Copyright Notice 43 Copyright (c) 2018 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 3 60 3. Frame Priority . . . . . . . . . . . . . . . . . . . . . . . 3 61 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 62 5. Security considerations . . . . . . . . . . . . . . . . . . . 4 63 6. Normative References . . . . . . . . . . . . . . . . . . . . 4 64 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 66 1. Introduction 68 Frame Marking RTP Header Extension [I-D.ietf-avtext-framemarking] 69 provides a single bit for marking frames that may be discarded by a 70 middle box for non-scalable streams. Having one bit for marking a 71 discardable frame provides the same information to a middle box that 72 need to drop few frames or many frames. An encoder may want to mark 73 multiple frames as discardable but with different drop priority, 74 allowing the middle box to discard part or all the discardable 75 frames. The middle box can use the priority information for deciding 76 which frames to drop. By monitoring the RTP stream and the frame 77 marking a middle box can estimate how many RTP packets are in each 78 priority and use this information for the dropping decision. 80 A video stream is composed of Group of Pictures (GOP) where the GOP 81 includes I,P and B frames. A GOP is typically bound by I frames and 82 is 15-30,60 frames long but can vary with frame rate, content 83 complexity and encoder implementation. There are a couple of use 84 cases that can benefit if discard priority is available. 86 o When there are contiguous non referenced B frames dropping all of 87 them will reduce the actual frame rate. By providing different 88 priority to each of these B frames the middle box can affect the 89 actual frame rate. This information can be also deducted based on 90 the number of contiguous frames but having priority will make it 91 easier for the middle box for example when the frames are 92 interleaved. 94 o When there are referenced B frames, for example a non referenced B 95 frame (B1) followed by a B frame (B2) referenced by B1 only. If 96 B1 is dropped then B2 can be dropped too. By using priority B1 97 can have lower priority than B2. 99 o Dropping a P frame that is close to the end of the GOP is also 100 possible comparing to a P frame in the beginning of the GOP. The 101 encoder can know when such P frame exist and mark is as 102 discardable with lowest priority. 104 2. Requirements Notation 106 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 107 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 108 document are to be interpreted as described in [RFC2119]. 110 3. Frame Priority 112 This memo adds two P bits to the RTP header extension defined in 113 [I-D.ietf-avtext-framemarking] section 3.1. 115 RTP Header Extension for non-scalable streams: 117 0 1 118 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 | ID=? | L=0 |S|E|I|D|P P 0 0| 121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 123 P: Priority bits (2 bits). If the D bit is set to zero these bits 124 MUST be zero. If the D bit is set to 1 the values 00 is the highest 125 drop priority (this will be the case when priority is not specified) 126 and 11 is the lowest drop priority. 128 The priority bits apply to a single RTP stream and a middle box MUST 129 NOT use this information to compare discardable frames from different 130 RTP streams. 132 Based on the use cases from the introduction, the priority of the non 133 referenced B frame will be 00, the priority of the referenced B 134 frames will be 01 and the priority of the discardable P frame will be 135 10. If the middle box drops the frames marked with priority 00 it 136 can now drop the frames marked with priority 01 since they are not 137 needed for decoding the stream. 139 4. IANA Considerations 141 There are no IANA actions 143 5. Security considerations 145 This memo does not add any security information to the ones in 146 [I-D.ietf-avtext-framemarking] 148 6. Normative References 150 [I-D.ietf-avtext-framemarking] 151 Berger, E., Nandakumar, S., and M. Zanaty, "Frame Marking 152 RTP Header Extension", draft-ietf-avtext-framemarking-08 153 (work in progress), October 2018. 155 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 156 Requirement Levels", BCP 14, RFC 2119, 157 DOI 10.17487/RFC2119, March 1997, 158 . 160 Authors' Addresses 162 Roni Even 163 Huawei Technologies 164 Tel Aviv 165 Israel 167 Email: Roni.even@huawei.com 169 Ofer Idan 170 Huawei Technologies 171 Hod Hasharon 172 Israel 174 Email: ofer.idan@huawei.com