[Standards] Jingle audio and G.711

Peter Saint-Andre stpeter at stpeter.im
Thu Apr 10 03:42:03 UTC 2008

Offlist, someone mentioned to me that it might be appropriate for
XEP-0167 to recommend or even require support for the ITU-T's G.711
technology, which is represented by payload-types 0 (PCMU) and 8 (PCMA)
as registered with the IANA.

Section 4.5.14 of RFC 3551 describes G.711 as follows:

   PCMA and PCMU are specified in ITU-T Recommendation G.711.  Audio
   data is encoded as eight bits per sample, after logarithmic scaling.
   PCMU denotes mu-law scaling, PCMA A-law scaling.  A detailed
   description is given by Jayant and Noll [15].  Each G.711 octet SHALL
   be octet-aligned in an RTP packet.  The sign bit of each G.711 octet
   SHALL correspond to the most significant bit of the octet in the RTP
   packet (i.e., assuming the G.711 samples are handled as octets on the
   host machine, the sign bit SHALL be the most significant bit of the
   octet as defined by the host machine format).  The 56 kb/s and 48
   kb/s modes of G.711 are not applicable to RTP, since PCMA and PCMU
   MUST always be transmitted as 8-bit samples.

More information about G.711 is available here:




Peter Saint-Andre

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