< draft-ietf-payload-flexible-fec-scheme-19.txt   draft-ietf-payload-flexible-fec-scheme-20.txt >
PAYLOAD M. Zanaty PAYLOAD M. Zanaty
Internet-Draft Cisco Internet-Draft Cisco
Intended status: Standards Track V. Singh Intended status: Standards Track V. Singh
Expires: September 29, 2019 callstats.io Expires: November 17, 2019 callstats.io
A. Begen A. Begen
Networked Media Networked Media
G. Mandyam G. Mandyam
Qualcomm Inc. Qualcomm Inc.
March 28, 2019 May 16, 2019
RTP Payload Format for Flexible Forward Error Correction (FEC) RTP Payload Format for Flexible Forward Error Correction (FEC)
draft-ietf-payload-flexible-fec-scheme-19 draft-ietf-payload-flexible-fec-scheme-20
Abstract Abstract
This document defines new RTP payload formats for the Forward Error This document defines new RTP payload formats for the Forward Error
Correction (FEC) packets that are generated by the non-interleaved Correction (FEC) packets that are generated by the non-interleaved
and interleaved parity codes from source media encapsulated in RTP. and interleaved parity codes from source media encapsulated in RTP.
These parity codes are systematic codes (Flexible FEC, or "FLEX These parity codes are systematic codes (Flexible FEC, or "FLEX
FEC"), where a number of FEC repair packets are generated from a set FEC"), where a number of FEC repair packets are generated from a set
of source packets from one or more source RTP streams. These FEC of source packets from one or more source RTP streams. These FEC
repair packets are sent in a redundancy RTP stream separate from the repair packets are sent in a redundancy RTP stream separate from the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 29, 2019. This Internet-Draft will expire on November 17, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Parity Codes . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Parity Codes . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1. One-Dimensional (1-D) Non-interleaved (Row) FEC 1.1.1. One-Dimensional (1-D) Non-interleaved (Row) FEC
Protection . . . . . . . . . . . . . . . . . . . . . 5 Protection . . . . . . . . . . . . . . . . . . . . . 5
1.1.2. 1-D Interleaved (Column) FEC Protection . . . . . . . 6 1.1.2. 1-D Interleaved (Column) FEC Protection . . . . . . . 6
1.1.3. Use Cases for 1-D FEC Protection . . . . . . . . . . 7 1.1.3. Use Cases for 1-D FEC Protection . . . . . . . . . . 7
1.1.4. Two-Dimensional (2-D) (Row and Column) FEC Protection 8 1.1.4. Two-Dimensional (2-D) (Row and Column) FEC Protection 8
1.1.5. FEC Protection with Flexible Mask . . . . . . . . . . 10 1.1.5. FEC Protection with Flexible Mask . . . . . . . . . . 10
1.1.6. FEC Overhead Considerations . . . . . . . . . . . . . 10 1.1.6. FEC Overhead Considerations . . . . . . . . . . . . . 10
1.1.7. FEC Protection with Retransmission . . . . . . . . . 10 1.1.7. FEC Protection with Retransmission . . . . . . . . . 10
1.1.8. Repair Window Considerations . . . . . . . . . . . . 10 1.1.8. Repair Window Considerations . . . . . . . . . . . . 11
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 11 2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 11
3. Definitions and Notations . . . . . . . . . . . . . . . . . . 11 3. Definitions and Notations . . . . . . . . . . . . . . . . . . 11
3.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 11 3.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 11
3.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2. Notations . . . . . . . . . . . . . . . . . . . . . . . . 12
4. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 12 4. Packet Formats . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. Source Packets . . . . . . . . . . . . . . . . . . . . . 12 4.1. Source Packets . . . . . . . . . . . . . . . . . . . . . 12
4.2. FEC Repair Packets . . . . . . . . . . . . . . . . . . . 13 4.2. FEC Repair Packets . . . . . . . . . . . . . . . . . . . 13
4.2.1. RTP Header of FEC Repair Packets . . . . . . . . . . 13 4.2.1. RTP Header of FEC Repair Packets . . . . . . . . . . 13
4.2.2. FEC Header of FEC Repair Packets . . . . . . . . . . 15 4.2.2. FEC Header of FEC Repair Packets . . . . . . . . . . 15
5. Payload Format Parameters . . . . . . . . . . . . . . . . . . 20 5. Payload Format Parameters . . . . . . . . . . . . . . . . . . 20
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o 2-D Parity FEC Protection: Overhead = 1/L + 1/D o 2-D Parity FEC Protection: Overhead = 1/L + 1/D
where L and D are the number of columns and rows in the source block, where L and D are the number of columns and rows in the source block,
respectively. respectively.
1.1.7. FEC Protection with Retransmission 1.1.7. FEC Protection with Retransmission
This specification supports both forward error correction, i.e. This specification supports both forward error correction, i.e.
before any loss is reported, as well as retransmission of source before any loss is reported, as well as retransmission of source
packets after loss is reported. The retransmission includes the RTP packets after loss is reported. The retransmission includes the RTP
header of the source packet in addition to the payload. Therefore, header of the source packet in addition to the payload. If a peer
endpoints supporting other RTP retransmission methods (see [RFC4588]) supporting both FLEX FEC and other RTP retransmission methods (see
in addition to FLEX FEC MUST only use the FLEX FEC retransmission [RFC4588]) receives an Offer including both FLEX FEC and another RTP
method. retransmission method, it MUST respond with an Answer containing only
FLEX FEC.
1.1.8. Repair Window Considerations 1.1.8. Repair Window Considerations
The value for the repair window duration is related to the maximum L The value for the repair window duration is related to the maximum L
and D values that are expected during a FLEX FEC session and and D values that are expected during a FLEX FEC session and
therefore cannot be chosen arbitrarily. Repair packets that include therefore cannot be chosen arbitrarily. Repair packets that include
L and D values larger than the repair window MUST not be sent. The L and D values larger than the repair window MUST not be sent. The
rate of the source streams should also be considered, as the repair rate of the source streams should also be considered, as the repair
window duration should ideally span several packetization intervals window duration should ideally span several packetization intervals
in order to leverage the error correction capabilities of the parity in order to leverage the error correction capabilities of the parity
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