RFC 3558 (rfc3558) - Page 2 of 23
RTP Payload Format for Enhanced Variable Rate Codecs (EVRC) and Selectable Mode Vocoders (SMV)
Alternative Format: Original Text Document
RFC 3558 RTP Payload Format for EVRC and SMV July 2003
9. Implementation Issues ......................................... 12
9.1. Interleaving Length .......................................12
9.2. Validation of Received Packets ............................13
9.3. Processing the Late Packets ...............................13
10. Mode Request ................................................. 13
11. Storage Format ............................................... 14
12. IANA Considerations .......................................... 15
12.1. Registration of Media Type EVRC ..........................15
12.2. Registration of Media Type EVRC0 .........................16
12.3. Registration of Media Type SMV ...........................17
12.4. Registration of Media Type SMV0 ..........................18
13. Mapping to SDP Parameters .................................... 19
14. Security Considerations ...................................... 20
15. Adding Support of Other Frame-Based Vocoders ................. 20
16. Acknowledgements ............................................. 21
17. References ................................................... 21
17.1 Normative ................................................ 21
17.2 Informative .............................................. 22
18. Author's Address ............................................. 22
19. Full Copyright Statement ..................................... 23
1. Introduction
This document describes how speech compressed with EVRC [1] or SMV
[2] may be formatted for use as an RTP payload type. The format is
also extensible to other codecs that generate a similar set of frame
types. Two methods are provided to packetize the codec data frames
into RTP packets: an interleaved/bundled format and a zero-header
format. The sender may choose the best format for each application
scenario, based on network conditions, bandwidth availability, delay
requirements, and packet-loss tolerance.
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 [3].
2. Background
The 3rd Generation Partnership Project 2 (3GPP2) has published two
standards which define speech compression algorithms for CDMA
applications: EVRC [1] and SMV [2]. EVRC is currently deployed in
millions of first and second generation CDMA handsets. SMV is the
preferred speech codec standard for CDMA2000, and will be deployed in
third generation handsets in addition to EVRC. Improvements and new
codecs will keep emerging as technology improves, and future handsets
will likely support multiple codecs.
Li Standards Track