RTP Payload Format for the Mixed Excitation Linear Prediction Enhanced (MELPe) Codec
RFC 8130

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Internet Engineering Task Force (IETF)                     V. Demjanenko
Request for Comments: 8130                                  D. Satterlee
Category: Standards Track                       VOCAL Technologies, Ltd.
ISSN: 2070-1721                                               March 2017

                           RTP Payload Format
   for the Mixed Excitation Linear Prediction Enhanced (MELPe) Codec

Abstract

   This document describes the RTP payload format for the Mixed
   Excitation Linear Prediction Enhanced (MELPe) speech coder.  MELPe's
   three different speech encoding rates and sample frame sizes are
   supported.  Comfort noise procedures and packet loss concealment are
   described in detail.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8130.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Demjanenko & Satterlee       Standards Track                    [Page 1]
RFC 8130           RTP Payload Format for MELPe Codec         March 2017

Table of Contents

   1. Introduction ....................................................2
      1.1. Conventions ................................................2
   2. Background ......................................................3
   3. Payload Format ..................................................4
      3.1. MELPe Bitstream Definitions ................................5
           3.1.1. 2400 bps Bitstream Structure ........................6
           3.1.2. 1200 bps Bitstream Structure ........................9
           3.1.3. 600 bps Bitstream Structure ........................13
      3.2. MELPe Comfort Noise Bitstream Definition ..................18
      3.3. Multiple MELPe Frames in an RTP Packet ....................20
      3.4. Congestion Control Considerations .........................21
   4. Payload Format Parameters ......................................22
      4.1. Media Type Definitions ....................................22
      4.2. Mapping to SDP ............................................23
      4.3. Declarative SDP Considerations ............................25
      4.4. Offer/Answer SDP Considerations ...........................25
   5. Discontinuous Transmissions ....................................26
   6. Packet Loss Concealment ........................................26
   7. IANA Considerations ............................................26
   8. Security Considerations ........................................27
   9. References .....................................................27
      9.1. Normative References ......................................27
      9.2. Informative References ....................................29
   Authors' Addresses ................................................30

1.  Introduction

   This document describes how compressed Mixed Excitation Linear
   Prediction Enhanced (MELPe) speech as produced by the MELPe codec
   may be formatted for use as an RTP payload.  Details are provided to
   packetize the three different codec bitrate data frames (2400, 1200,
   and 600) into RTP packets.  The sender may send one or more codec
   data frames per packet, depending on the application scenario or
   based on transport network conditions, bandwidth restrictions, delay
   requirements, and packet loss tolerance.

1.1.  Conventions

   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 RFC 2119 [RFC2119].

   Best current practices for writing an RTP payload format
   specification were followed [RFC2736].

Demjanenko & Satterlee       Standards Track                    [Page 2]
RFC 8130           RTP Payload Format for MELPe Codec         March 2017

2.  Background

   The MELP speech coder was developed by the US military as an upgrade