RFC 3267 (rfc3267) - Page 2 of 49
Real-Time Transport Protocol (RTP) Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs
Alternative Format: Original Text Document
RFC 3267 RTP Payload Format for AMR and AMR-WB June 2002
Table of Contents
1. Introduction.................................................... 3
2. Conventions and Acronyms........................................ 3
3. Background on AMR/AMR-WB and Design Principles.................. 4
3.1. The Adaptive Multi-Rate (AMR) Speech Codec.................. 4
3.2. The Adaptive Multi-Rate Wideband (AMR-WB) Speech Codec...... 5
3.3. Multi-rate Encoding and Mode Adaptation..................... 5
3.4. Voice Activity Detection and Discontinuous Transmission..... 6
3.5. Support for Multi-Channel Session........................... 6
3.6. Unequal Bit-error Detection and Protection.................. 7
3.6.1. Applying UEP and UED in an IP Network................... 7
3.7. Robustness against Packet Loss.............................. 9
3.7.1. Use of Forward Error Correction (FEC)................... 9
3.7.2. Use of Frame Interleaving...............................11
3.8. Bandwidth Efficient or Octet-aligned Mode...................11
3.9. AMR or AMR-WB Speech over IP scenarios......................12
4. AMR and AMR-WB RTP Payload Formats..............................14
4.1. RTP Header Usage............................................14
4.2. Payload Structure...........................................16
4.3. Bandwidth-Efficient Mode....................................16
4.3.1. The Payload Header......................................16
4.3.2. The Payload Table of Contents...........................17
4.3.3. Speech Data.............................................19
4.3.4. Algorithm for Forming the Payload.......................20
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.........................30
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...............................33
5. AMR and AMR-WB Storage Format...................................34
5.1. Single Channel Header.......................................34
5.2. Multi-channel Header........................................35
5.3. Speech Frames...............................................36
6. Congestion Control..............................................37
7. Security Considerations.........................................37
7.1. Confidentiality.............................................37
Sjoberg, et. al. Standards Track