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Re: Audio/AMR

From: Jeff Bouis <jbouis@lucent.com>
Date: Mon, 22 Apr 2002 12:46:31 -0500
Message-ID: <3CC44C77.68EC0FA8@lucent.com>
To: James Salsman <james@bovik.org>
CC: discuss@apps.ietf.org, vpim@lists.neystadt.org, jutta@pobox.com

First was GSM 06.10 (full rate, or GSM-FR) at 13 kbps.  Later GSM 06.20
appeared (half rate, or GSM-HR) at 5.6 kbps, and then came GSM 06.60
(enhanced full rate, or GSM-EFR) at 12.2 kbps.

Finally came GSM 06.90 (Adapative Multi-Rate, or GSM-AMR), at variable
bitrates.  It encompasses 8 different birate modes, and some of those
happen to be the same codec used in other systems:

    12.20 kbps (GSM-EFR codec, and also TIA TDMA-US1 enhanced codec)
    10.20 kbps
     7.95 kpbs
     7.40 kbps (TIA/EIA IS-641 TDMA EFR codec)
     6.70 kpbs (PDC-EFR, or ARIB EFR codec)
     5.90 kbps
     5.15 kbps
     4.75 kpbs

Note that none of these are GSM 06.10, so to answer your question,
Audio/AMR is NOT the same as GSM 06.10.

UMTS also adopted AMR as its mandatory codec set.  The UMTS document set
is virtually identical to the GSM set, and with regard to the codecs
those changes are not significant.

An introduction to the overall coding system is available as GSM 06.71. 
In particular, the codec itself is specified by GSM 06.90, source code
is available in GSM 06.73, and test vectors in GSM 06.74.  (In the UMTS
set, these correspond to 3GPP TS 26.071, 26.090, 26.073, and 26.074,
respectively.)  All of these documents are available for free (after
registration) from http://pda.etsi.org/pda



James Salsman wrote:
> I have almost convinced myself that Audio/AMR is not the same as GSM 6.10
> -- can anyone please confirm or deny this?
> Here is an Audio/AMR reference implementation for x86 PCs:
> http://www.3gpp.org/ftp/tsg_sa/WG4_CODEC/AMR-Wideband/AMR-WB_Characterization_Phase/Executables/g7221%26amrnb400_exe.zip
> Does anyone have source to an AMR codec?  I can't find it.
> > AMR is the mandatory format for voice message audio email attachments
> > according to the MMS (Multimedia Messaging System) ETSI cellular
> > telephone specification (ETSI 123 140), which incorporates the IETF MIME
> > and VPIM specifications in large part.
> >
> > The MIME type registration for Audio/AMR is presently at:
> >   http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-amr-13.txt
> >
> > The AMR specification is:  3GPP TS 26.101:
> >   http://www.3gpp.org/ftp/tsg_sa/tsg_sa/TSGS_06/Docs/PDF/SP-99562.pdf
> Best wishes,
> James
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Received on Monday, 22 April 2002 15:58:54 UTC

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