(RFC 3952 published December 2004)

MIME media type name: audio

MIME subtype: iLBC

Optional parameters:

All of the parameters does apply for RTP transfer only.

maxptime:The maximum amount of media which can be encapsulated in
         each packet, expressed as time in milliseconds.  The time
         SHALL be calculated as the sum of the time the media present
         in the packet represents.  The time SHOULD be a multiple of
         the frame size.  This attribute is probably only meaningful
         for audio data, but may be used with other media types if it
         makes sense.  It is a media attribute, and is not dependent
         on charset.  Note that this attribute was introduced after
         RFC 2327, and non updated implementations will ignore this
         attribute.

mode:    The iLBC operating frame mode (20 or 30 ms) that will be
         encapsulated in each packet.  Values can be 0, 20 and 30
         (where 0 is reserved, 20 stands for preferred 20 ms frame
         size and 30 stands for preferred 30 ms frame size).

ptime:   Defined as usual for RTP audio (see [5]).

Encoding considerations:
         This type is defined for transfer via both RTP (RFC 3550)
         and stored-file methods as described in Section 4.1, of RFC
         3952.  Audio data is binary data, and must be encoded for
         non-binary transport; the Base64 encoding is suitable for
         email.

Security considerations:
         See Section 6 of RFC 3952.

Public specification:
         Please refer to RFC 3951 [1].

Additional information:
         The following applies to stored-file transfer methods:

         Magic number:
         ASCII character string for:
         o 30 ms frame size mode "#!iLBC30\n" (or 0x23 0x21
         0x69 0x4C 0x42 0x43 0x33 0x30 0x0A in hexadecimal)
         o 20 ms frame size mode "#!iLBC20\n" (or 0x23 0x21
         0x69 0x4C 0x42 0x43 0x32 0x30 0x0A in hexadecimal)

         File extensions: lbc, LBC
         Macintosh file type code: none
         Object identifier or OID: none

Person & email address to contact for further information:
         alan.duric&telio.no

Intended usage: COMMON.
         It is expected that many VoIP applications will use this
         type.

Author/Change controller:
         alan.duric&telio.no
         IETF Audio/Video transport working group