RTP Payload Format for Elementary Streams with MPEG Surround Multi-Channel Audio
RFC 5691

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Network Working Group                                         F. de Bont
Request for Comments: 5691                           Philips Electronics
Updates: 3640                                                  S. Doehla
Category: Standards Track                                 Fraunhofer IIS
                                                              M. Schmidt
                                                      Dolby Laboratories
                                                        R. Sperschneider
                                                          Fraunhofer IIS
                                                            October 2009

               RTP Payload Format for Elementary Streams
                 with MPEG Surround Multi-Channel Audio

Abstract

   This memo describes extensions for the RTP payload format defined in
   RFC 3640 for the transport of MPEG Surround multi-channel audio.
   Additional Media Type parameters are defined to signal backwards-
   compatible transmission inside an MPEG-4 Audio elementary stream.  In
   addition, a layered transmission scheme that doesn't use the MPEG-4
   systems framework is presented to transport an MPEG Surround
   elementary stream via RTP in parallel with an RTP stream containing
   the downmixed audio data.

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (c) 2009 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
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   described in the BSD License.

de Bont, et al.             Standards Track                     [Page 1]
RFC 5691               Transport of MPEG Surround           October 2009

Table of Contents

   1. Introduction ....................................................2
   2. Conventions .....................................................3
   3. Definitions and Abbreviations ...................................3
      3.1. Definitions ................................................3
      3.2. Abbreviations ..............................................4
   4. Transport of MPEG Surround ......................................4
      4.1. Embedded Spatial Audio Data in AAC Payloads ................4
      4.2. MPEG Surround Elementary Stream ............................5
           4.2.1. Low Bitrate MPEG Surround ...........................7
           4.2.2. High Bitrate MPEG Surround ..........................8
   5. IANA Considerations .............................................8
      5.1. Media Type Registration ....................................9
      5.2. Registration of Mode Definitions with IANA .................9
      5.3. Usage of SDP ..............................................10
   6. Security Considerations ........................................10
   7. References .....................................................11
      7.1. Normative References ......................................11
      7.2. Informative References ....................................11

1.  Introduction

   MPEG Surround (Spatial Audio Coding, SAC) [23003-1] is an
   International Standard that was finalized by MPEG in January 2007.
   It is capable of re-creating N channels based on M < N transmitted
   channels and additional control data.  In the preferred modes of
   operating the Spatial Audio Coding system, the M channels can either
   be a single mono channel or a stereo channel pair.  The control data
   represents a significantly lower data rate than the data rate
   required for transmitting all N channels, making the coding very
   efficient while at the same time ensuring compatibility with M
   channel devices.

   The MPEG Surround standard incorporates a number of tools that enable
   features that allow for broad application of the standard.  A key
   feature is the ability to scale the spatial image quality gradually
   from very low spatial overhead towards transparency.  Another key
   feature is that the decoder input can be made compatible to existing
   matrixed surround technologies.

   As an example, for 5.1 multi-channel audio, the MPEG Surround encoder
   creates a stereo (or mono) downmix signal and spatial information