Toll Quality Voice - 32 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) MIME Sub-type Registration
draft-ietf-vpim-vpimv2r2-32k-03

The information below is for an old version of the document that is already published as an RFC
Document Type RFC Internet-Draft (vpim WG)
Authors Glenn Parsons  , Gregory Vaudreuil 
Last updated 2015-10-14 (latest revision 2002-02-15)
Stream Internet Engineering Task Force (IETF)
Formats plain text pdf htmlized bibtex
Stream WG state (None)
Document shepherd No shepherd assigned
IESG IESG state RFC 3802 (Draft Standard)
Consensus Boilerplate Unknown
Telechat date
Responsible AD Ned Freed
Send notices to <jwn2@qualcomm.com>
Network Working Group                                   Greg Vaudreuil 
    Internet Draft                                     Lucent Technologies 
    Expires in six months                                    Glenn Parsons 
    Obsoletes: RFC 2422                                    Nortel Networks 
                                                         February 14, 2002 
     
                                           
                      Toll Quality Voice - 32 kbit/s ADPCM 
                           MIME Sub-type Registration 
                                         
                      <draft-ietf-vpim-vpimv2r2-32k-03.txt> 
     
     
    Status of this Memo 
     
       This document is an Internet-Draft and is in full conformance with 
       all provisions of Section 10 of RFC2026.  
        
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     Abstract  
       
       This document is an Internet-Draft and is in full conformance with 
       This document describes the registration of the MIME sub-type 
       audio/32KADPCM for toll quality audio.  This audio encoding is 
       defined by the ITU-T in Recommendation G.726. 
        
       This document obsoletes RFC 2422. 
        
        
     Copyright Notice  
     
       Copyright (C) The Internet Society (2002).  All Rights Reserved. 
     
       



    Internet Draft             32 kbit/s ADPCM           February 14, 2002 
     

       
      1.  Introduction 
       
      This document describes the registration of the MIME sub-type 
      audio/32KADPCM for toll quality audio.  This audio encoding is 
      defined by the ITU-T in Recommendation G.726.  This document 
      obsoletes an earlier sub-type registration contained in RFC 1911.  
      This document also obsoletes RFC 2422. 
     
      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
      "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in 
      this document are to be interpreted as described in [REQ]. 
       
       
      2. ITU-T Definition 
       
      Recommendation G.726 [G726] defines the characteristics that are 
      recommended for the conversion of a 64 kbit/s A-law or m-law pulse 
      code modulation (PCM) channel at 8000 samples/second to and from a 
      40, 32, 24 or 16 kbit/s channel. The conversion is applied to the 
      PCM bit stream using an adaptive differential pulse code modulation 
      (ADPCM) transcoding technique.  This Recommendation obsoletes G.721 
      which only defined the 32 kbit/s characteristics. 
       
      Recommendation G.726 was prepared by Study Group 15 of the 
      Telecommunications Standardization Sector of the International 
      Telecommunication Union (ITU-T) and was approved under the ITU's 
      Resolution No. 2 procedure on the 14 of December 1990. 
       
       
      3. MIME Definition 
       
      3.1 audio/32KADPCM 
       
      CCITT Recommendation G.726 [G726] describes the algorithm 
      recommended for conversion of a 64 kbit/s A-law or u-law PCM channel 
      to and from a 32 kbit/s channel (this is the same algorithm as 
      described in the deprecated G.721).  The conversion is applied to 
      the PCM stream using an Adaptive Differential Pulse Code Modulation 
      (ADPCM) transcoding technique. 

      The MIME sub-type audio/32KADPCM is defined to hold binary audio 
      data encoded in 32 kbit/s ADPCM exactly as defined by ITU-T 
      Recommendation G.726.  No header information shall be included as 
      part of the audio data.  The content transfer encoding is typically 
      either binary or base64. 
       
      An additional consideration that this document defines for clarity 
      is the choice of little endian ordering of the four bit code words.  
      This default ordering is defined in ITU-T Recommendation X.420 
      [X420] for the equivalent X.400 body part, but is also detailed 
      below in the IANA Registration. 
       

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      3.2 VPIM Usage 
       
      The audio/32KADPCM sub-type is a primary component of the VPIM 
      specification [VPIM].  In this context, the Content-Description and 
      Content-Disposition headers are used to succinctly describe the 
      contents of the audio body.  As well, only the little endian bit 
      ordering is valid.  Refer to the VPIM Specifcation for proper usage. 
       
       
      4.  IANA Registration 
       
           To: ietf-types@iana.org 
           Subject: Registration of MIME media type audio/32KADPCM 
       
           MIME media type name: audio 
       
           MIME subtype name: 32KADPCM 
       
           Required parameters: none 
       
           Optional parameters: none 
       
           Encoding considerations:  
       
              Binary or Base-64 generally preferred 
       
           Security considerations:  
       
              There are no known security risks with the sending or 
              playing of raw audio data  Audio data is typically 
              interpreted only by an audio codec.  Unintended information 
              introduced into the data stream will result in noise. 
     
       
           Interoperability considerations:  
       
              The four bit code word ordering within a byte may differ 
              between existing implementations of G.726 codecs.  Since 
              this content only permits the little endian ordering, codecs 
              that support the opposite ordering must reorder the code 
              words before storing to or retrieving from this content 
              type. 
               
       
           Published specification:  
       
                   ITU-T G.726 with little endian ordering 
       
           Applications which use this media type:  
       
                   Primarily voice messaging 
       

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           Additional information: 
       
             Magic number(s): ? 
             File extension(s): .726 
             Macintosh File Type Code(s):  APCM 
                 
              Little Endian Ordering: 
       
              The 4-bit code words of the G.726 encoding MUST be packed 
              into octets/bytes as follows:  the first code word (A) is 
              placed in the four least significant bits of the first 
              octet, with the least significant bit (LSB) of the code word 
              (A0) in the least significant bit of the octet;  the second 
              code word (B) is placed in the four most significant bits of 
              the first octet, with the most significant bit (MSB) of the 
              code word (B3) in the most significant bit of the octet.  
              Subsequent pairs of the code words shall be packed in the 
              same way into successive octets, with the first code word of 
              each pair placed in the least significant four bits of the 
              octet.  It is preferred that the voice sample be extended 
              with silence such that the encoded value comprises an even 
              number of code words.  However, if the voice sample 
              comprises an odd number of code words, then the last code 
              word shall be discarded. 
               
       
                      +--+--+--+--+--+--+--+--+  
                      |B3|B2|B1|B0|A3|A2|A1|A0|  
                      +--+--+--+--+--+--+--+--+  
              MSB ->  | 7| 6| 5| 4| 3| 2| 1| 0|  <- LSB  
                      +--+--+--+--+--+--+--+--+  
        
                      32K ADPCM / Octet Mapping  
       
                 
           Person & email address to contact for further information: 
       
             Glenn W. Parsons  
             gparsons@NortelNetworks.com   
       
             Gregory M. Vaudreuil  
             GregV@ieee.org 
       
           Intended usage: COMMON 
       
           Author/Change controller: 
       
             Glenn W. Parsons & Gregory M. Vaudreuil  
       
       

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       4. Security Considerations 

     
      There are no known security risks with the sending or playing of raw 
      audio data  Audio data is typically interpreted only by an audio 
      codec.  Unintended information introduced into the data stream will 
      result in noise. 

     
      5. Authors' Addresses 

       Glenn W. Parsons 
       Nortel Networks 
       P.O. Box 3511, Station C 
       Ottawa, ON  K1Y 4H7 
       Canada 
        
       Phone: +1-613-763-7582 
       Fax:   +1-613-763-2697 
        
       Email: gparsons@nortelnetworks.com 
        
        
       Gregory M. Vaudreuil 
       Lucent Technologies 
       7291 Williamson Rd 
       Dallas, TX  75214 
       United States 
        
       Phone/Fax: +1-972-733-2722 
       Email: gregv@ieee.org 
        
       
       
      6. References 

      [G726] CCITT Recommendation G.726 (1990), General Aspects of Digital 
           Transmission Systems, Terminal Equipment - 40, 32, 24,16 kbit/s 
           Adaptive Differential Pulse Code Modulation (ADPCM).   

      [MIME4] N. Freed and N. Borenstein,  "Multipurpose Internet Mail 
           Extensions (MIME) Part Four: Registration Procedures", RFC 
           2048, Innosoft, First Virtual, Nov 1996. 

      [VPIM1] Vaudreuil, Greg, "Voice Profile for Internet Mail", RFC 
           1911, Feb 1996. 

      [VPIM2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet 
           Mail - version 2", RFC 2421, September 1998. 

      [VPIM2R2] Vaudreuil, G., and G. Parsons, "Voice Profile for Internet 
           Mail - version 2", <draft-ietf-vpim-vpimv2r2-04.txt>, October 
           22, 2001. 

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      [X420] ITU-T Recommendation X.420 (1996) - ISO/IEC 10021-7:1996, 
           Message handling systems: Interpersonal messaging. 

      [REQ] S. Bradner, "Key words for use in RFCs to Indicate Requirement 
           Levels", RFC 2119, March 1997. 

     
     
      7.  Changes from RFC 2422 

       Only editoral and boilerplate changes from RFC 2424 have been made 
       to this document. 
     
     
      8.  Full Copyright Statement 

       Copyright (C) The Internet Society (2002).  All Rights Reserved. 
        
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