RFC Errata
RFC 4867, "RTP Payload Format and File Storage Format for the Adaptive Multi-Rate (AMR) and Adaptive Multi-Rate Wideband (AMR-WB) Audio Codecs", April 2007
Source of RFC: avt (rai)See Also: RFC 4867 w/ inline errata
Errata ID: 4349
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Thomas Belling
Date Reported: 2015-04-27
Verifier Name: Ben Campbell
Date Verified: 2016-05-25
Section 8.1 says:
mode-set: Restricts the active codec mode set to a subset of all modes, for example, to be able to support transport channels such as GSM networks in gateway use cases. Possible values are a comma separated list of modes from the set: 0,...,7 (see Table 1a [2]). The SID frame type 8 and NO_DATA (frame type 15) are never included in the mode set, but can always be used. If mode-set is specified, it MUST be abided, and frames encoded with modes outside of the subset MUST NOT be sent in any RTP payload or used in codec mode requests. If not present, all codec modes are allowed for the payload type.
It should say:
mode-set: Restricts the active codec mode set to a subset of all modes, for example, to be able to support transport channels such as GSM networks in gateway use cases. Possible values are a comma separated list of modes from the set: 0,...,7 (see Table 1a [2]). The SID frame type 8 and NO_DATA (frame type 15) are never included in the mode set, but can always be used. If mode-set is specified, it MUST be abided, i.e. frames encoded with modes outside of the subset MUST NOT be sent in any RTP payload and codec mode requests MUST only use modes within the mode-set or CMR=15. If the mode-set parameter is not present, then all codec modes are allowed for the payload type.
Notes:
The existing text rules out that CMR=15 is used when a mode-set has been negotiated. However, this contradicts a statement in .clause 4.3.1 that if a terminal has no preference in which mode to receive, it SHOULD set CMR=15 in all its outbound payloads.
This erratum has been discussed and endorsed by the 3GPP SA4 group before submission to IETF.