(RFC 5188 published February 2008, subtype last updated February 2008)

Type name: audio

Subtype name: EVRCWB

Required parameters: None

Optional parameters:

These parameters apply to RTP transfer only.

mode-set-recv: A subset of EVRC-WB modes.  Possible values are a
comma-separated list of modes from the set {0,4,7} (see Table
2.5.1.2-1 in 3GPP2 C.S0014-C).  A decoder can use this attribute to
inform an encoder of its preference to operate in a specified subset
of modes.  Absence of this parameter signals the mode set {0,4,7}.

sendmode: A mode of the EVRC-WB codec.  An encoder can use this to
signal its current mode of operation.  Possible values are 0,4,7 (see
Table 2.5.1.2-1 in 3GPP2 C.S0014-C).  Absence of this parameter
signals mode 0.

ptime: See RFC 8866.

maxptime: See RFC 8866.

maxinterleave: Maximum number for interleaving length (field LLL in
the Interleaving Octet)[0..7].  The interleaving lengths used in the
entire session MUST NOT exceed this maximum value.  If not signaled,
the maxinterleave length MUST be 5.

silencesupp: See Section 6.1 in RFC 4788.

dtxmax: See Section 6.1 in RFC 4788.

dtxmin: See Section 6.1 in RFC 4788.

hangover: See Section 6.1 in RFC 4788.

Encoding considerations:

This media type is framed binary data (see RFC 4288, Section 4.8) and
is defined for transfer of EVRC-WB encoded data via RTP using the
interleaved/bundled packet format specified in RFC 3558.

Security considerations: See Section 18 of RFC 5188.

Interoperability considerations: None

Published specification:

The EVRC-WB vocoder is specified in 3GPP2 C.S0014-C.  The transfer
method with the interleaved/bundled packet format via RTP is
specified in RFC 3558 and RFC 5188.

3GPP2 C.S0050-B, 3GPP2 File Formats for Multimedia Services.

3GPP2 specifications are publicly accessible at http://www.3gpp2.org

Applications that use this media type:

It is expected that many VoIP applications (as well as mobile
applications) will use this type.

Additional information:

The following applies to stored-file transfer methods:

Magic number: #!EVCWB\n (see Section 8 of RFC 5188)

File extensions: evw, EVW

Macintosh file type code: None

Object identifier or OID: None

EVRC-WB speech frames may also be stored in the file format "3g2"
defined in 3GPP2 C.S0050-B, which is identified using the media types
"audio/3gpp2" or "video/3gpp2" registered by RFC 4393.

Person & email address to contact for further information:

Harikishan Desineni <hd&qualcomm.com>

Intended usage: COMMON

Restrictions on usage:

When this media type is used in the context of transfer over RTP, the
RTP payload format specified in Section 4.1 of RFC 3558 SHALL be
used.  In all other contexts, the file format defined in Section 8 of
RFC 5188 SHALL be used.

Author:

Harikishan Desineni

Change controller:

IETF Audio/Video Transport working group delegated from the IESG.