RFC 3558 (rfc3558) - Page 2 of 23


RTP Payload Format for Enhanced Variable Rate Codecs (EVRC) and Selectable Mode Vocoders (SMV)



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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


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