draft-flaks-audio-ac3

Last Version:	draft-flaks-audio-ac3-00.txt		Tracker Entry
Date:	01-Sep-2001
Disposition:	removed

Internet Engineering Task Force                                J. Flaks
Internet Draft                                       Dolby Laboratories
Document: draft-flaks-audio-ac3-00.txt                          October
Category: Audio MIME type 
 
 
                        The audio/ac3 Media Type 
 
 
Status of this Memo 
 
   This document is an Internet-Draft and is in full conformance with  
   all provisions of Section 10 of RFC2026 [1].  
    
   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups. Note that 
   other groups may also distribute working documents as Internet-
   Drafts. Internet-Drafts are draft documents valid for a maximum of 
   six months and may be updated, replaced, or obsoleted by other 
   documents at any time. It is inappropriate to use Internet- Drafts 
   as reference material or to cite them other than as "work in 
   progress." 
     
   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt 
     
   The list of Internet-Draft Shadow Directories can be accessed at 
   http://www.ietf.org/shadow.html. 
 
 
. Abstract 
    
   In recent years we have begun to see a convergence of Internet 
   technologies with traditional media formats such as video and audio. 
   It is therefore likely that movies and television with surround 
   sound capabilities are soon to be dispersed around the Internet.  
   AC-3 is standard multi-channel compression format for HDTV, DVD, and 
   other video formats, but there is no uniform MIME type for these 
   files.                       

    
. Conventions used in this document 
    
   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 RFC-2119 [2]. 
    
    
. AC-3 Audio 
    
   The audio compression method defined as AC-3 as described in ATSC-
   Digital Audio Compression Standard [4] is a popular method of 
   compressing multi-channel audio while maintaining high fidelity. 
    
  
                       The audio/ac3 Media Type           October 2000 
 
 
   An AC-3 frame contains 1536 samples of compressed data, as well as 
   other bit stream information.  Data rates vary from 32 kbps to 640 
   kbps. 
    
   The audio data is compressed by using a psychoacoustic model to 
   determine what data is inaudible to the human ear. Then unnecessary 
   data is removed from the bit stream.    
    
    
. MIME Types 
    
   MIME media type name:                audio 
   MIME subtype name:                   ac3 
    
   Required parameters:                 none 
   Optional parameters:                 none 
   Encoding considerations:             AC-3 audio data is binary data.  
                                        Base 64 encoding is suitable for 
                                        Email. 
   Security considerations:             None known at the time of 
                                        writing 
   Interoperability considerations:     None known at the time of 
                                        writing 
   Published specification:             See [4] 
   Applications:                        Multi-channel audio encoding 
   Additional information: 
    
   Magic number(s):                     None 
   File extension(s):                   .ac3 
   Macintosh File Type Code(s):         None 
   Object Identifier(s) or OID(s):      None 
    
   Personal information:                Jason Flaks 
   Email:                               jsf@dolby.com 
    
   Intended usage:                      COMMON 
    
   Author/Change controller:            jsf@dolby.com 
 
 
. Formal Syntax 
 
   The following syntax specification uses the augmented Backus-Naur 
   Form (BNF) as described in RFC-2234 [3]. 
    
    
. References
 
     Bradner, S., "The Internet Standards Process -- Revision 3", BCP 
      9, RFC 2026, October 1996. 
    


  
                       The audio/ac3 Media Type           October 2000 
 
 
 
     Bradner, S., "Key words for use in RFCs to Indicate Requirement 
      Levels", BCP 14, RFC 2119, March 1997 
    
     Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax 
      Specifications: ABNF", RFC 2234, Internet Mail Consortium and 
      Demon Internet Ltd., November 1997 
    
     U.S. Advanced Television Systems Committee, _Digital Audio  
      Compression (AC-3) Standard,_ Doc. A/52. Dec. 20, 1995 
 
    
. Author's Addresses 
    
   Jason Flaks 
   Dolby Labs 
   100 Potrero Ave 
   San Francisco, CA 94103 
   Phone: (415)558-0373  
   Email: jsf@dolby.com 
    
































  
                       The audio/ac3 Media Type           October 2000 
 
 
    
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