RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs
RFC 4867
Document | Type |
RFC - Proposed Standard
(April 2007; Errata)
Obsoletes RFC 3267
|
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Authors | Johan Sjoberg , Ari Lakaniemi , Magnus Westerlund , Qiaobing Xie | ||
Last updated | 2020-01-21 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Reviews | |||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 4867 (Proposed Standard) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Cullen Jennings | ||
Send notices to | fluffy@cisco.com |
Network Working Group J. Sjoberg Request for Comments: 4867 M. Westerlund Obsoletes: 3267 Ericsson Category: Standards Track A. Lakaniemi Nokia Q. Xie Motorola April 2007 RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs 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) The IETF Trust (2007). Abstract This document specifies a Real-time Transport Protocol (RTP) payload format to be used for Adaptive Multi-Rate (AMR) and Adaptive Multi- Rate Wideband (AMR-WB) encoded speech signals. The payload format is designed to be able to interoperate with existing AMR and AMR-WB transport formats on non-IP networks. In addition, a file format is specified for transport of AMR and AMR-WB speech data in storage mode applications such as email. Two separate media type registrations are included, one for AMR and one for AMR-WB, specifying use of both the RTP payload format and the storage format. This document obsoletes RFC 3267. Sjoberg, et al. Standards Track [Page 1] RFC 4867 RTP Payload Format for AMR and AMR-WB April 2007 Table of Contents 1. Introduction ....................................................4 2. Conventions and Acronyms ........................................4 3. Background on AMR/AMR-WB and Design Principles ..................5 3.1. The Adaptive Multi-Rate (AMR) Speech Codec .................5 3.2. The Adaptive Multi-Rate Wideband (AMR-WB) Speech Codec .....6 3.3. Multi-Rate Encoding and Mode Adaptation ....................6 3.4. Voice Activity Detection and Discontinuous Transmission ....7 3.5. Support for Multi-Channel Session ..........................7 3.6. Unequal Bit-Error Detection and Protection .................8 3.6.1. Applying UEP and UED in an IP Network ...............8 3.7. Robustness against Packet Loss ............................10 3.7.1. Use of Forward Error Correction (FEC) ..............10 3.7.2. Use of Frame Interleaving ..........................12 3.8. Bandwidth-Efficient or Octet-Aligned Mode .................12 3.9. AMR or AMR-WB Speech over IP Scenarios ....................13 4. AMR and AMR-WB RTP Payload Formats .............................15 4.1. RTP Header Usage ..........................................15 4.2. Payload Structure .........................................17 4.3. Bandwidth-Efficient Mode ..................................17 4.3.1. The Payload Header .................................17 4.3.2. The Payload Table of Contents ......................18 4.3.3. Speech Data ........................................20 4.3.4. Algorithm for Forming the Payload ..................21 4.3.5. Payload Examples ...................................21 4.3.5.1. Single-Channel Payload Carrying a Single Frame ..............................21 4.3.5.2. Single-Channel Payload Carrying Multiple Frames ...........................22 4.3.5.3. Multi-Channel Payload Carrying Multiple Frames ...........................23 4.4. Octet-Aligned Mode ........................................25 4.4.1. The Payload Header .................................25 4.4.2. The Payload Table of Contents and Frame CRCs .......26 4.4.2.1. Use of Frame CRC for UED over IP ..........28 4.4.3. Speech Data ........................................30 4.4.4. Methods for Forming the Payload ....................31 4.4.5. Payload Examples ...................................32 4.4.5.1. Basic Single-Channel Payload Carrying Multiple Frames ..................32 4.4.5.2. Two-Channel Payload with CRC, Interleaving, and Robust Sorting ..........32 4.5. Implementation Considerations .............................33Show full document text