rfc3190.txt

RFC 的详细文档！

   Interoperability considerations: NONE

   Published specification:
      RFC 3190.

   Applications which use this media type:
      Audio communication.

   Additional information:
      Magic number(s): None
      File extension(s): None
      Macintosh File Type Code(s): None

   Person & email address to contact for further information:
      Katsushi Kobayashi
      e-mail: [e-mail]

   Intended usage: COMMON

   Author/Change controller:
      Katsushi Kobayashi
      e-mail: [e-mail]












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9.  Security Considerations

   RTP packets using the payload format defined in this specification
   are subject to the security considerations discussed in the RTP
   specification [1], and any appropriate RTP profile [2].  This implies
   that confidentiality of the media streams is achieved by encryption.
   Because the data compression used along with this payload format is
   applied end-to-end, encryption may be performed after compression so
   there is no conflict between the two operations.

   A potential denial-of-service threat exists for data encodings using
   compression techniques that have non-uniform receiver-end
   computational load.  The attacker can inject pathological datagrams
   into the stream which are complex to decode and cause the receiver to
   be overloaded.  However, this encoding does not exhibit any
   significant non-uniformity.

   As with any IP-based protocol, in some circumstances a receiver may
   be overloaded simply by the receipt of too many packets, either
   desired or undesired.  Network-layer authentication may be used to
   discard packets from undesired sources, but the processing cost of
   the authentication itself may be too high.  In a multicast
   environment, pruning of specific sources may be implemented in future
   versions of IGMP [9] and in multicast routing protocols to allow a
   receiver to select which sources are allowed to reach it.

10.  IANA Considerations

   This document defines two new MIME subtype-specific optional
   parameters "emphasis" and "channel-order", which are specified with
   the sets of permissible values for those parameters in Sections 5 and
   7, respectively.  Section 8 includes registrations for three new MIME
   subtypes that use those optional parameters.  These registrations
   define the subset of the optional parameter values allowed for each
   subtype.  It is expected that the number of additional values that
   will need to be defined for these optional parameters is small.
   Therefore, anyone wishing to define new values is required to produce
   a revision of this document to be vetted through the normal Internet
   Standards process.












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11.  References

   [1] Schulzrinne, H., Casner, S., Frederick, R. and V. Jacobson, "RTP:
       A Transport Protocol for real-time applications," RFC 1889,
       January 1996.

   [2] H. Schulzrinne, "RTP profile for audio and video conferences with
       minimal control", RFC 1890, January 1996.

   [3] IEC 61119, Digital audio tape cassette system (DAT), November
       1992.

   [4] IEC 61834, Helical-scan digital video cassette recording system
       using 6,35 mm magnetic tape for consumer use (525-60, 625-50,
       1125-60 and 1250-50 systems), August 1998.

   [5] Salsman, J., "The Audio/L16 MIME content type", RFC 2586, May
       1999.

   [6] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [7] Handley, M. and V. Jacobson, "SDP: Session Description Protocol",
       RFC 2327, April 1998.

   [8] Kobayashi, K., Ogawa, A., Casner, S. and C. Bormann, "RTP Payload
       Format for DV (IEC 61834) Video", RFC 3189, January 2002.

   [9] Deering, S., "Host Extensions for IP Multicasting", STD 5, RFC
       1112, August 1989.





















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Appendix

   The DV audio channel symbols are specified in Table 2.  These symbols
   are taken from the notation used in the DV video specification IEC
   61834-4 [4], chapter 8.1.  For the exact meaning of each symbol, the
   original DV video specification should be consulted.

      L: Left channel of stereo
      R: Right channel of stereo
      M: Monaural signal
      C: Center channel of 3,4,6 or 8 channel audio
      S: Surround channel of 4 channel audio
      Ls, Ls1, Ls2: Left surround channel
      Rs, Rs1, Rs2: Right surround channel
      Lc: Left center channel of 8 channel audio
      Rc: Right center channel of 8 channel audio
      Wo: Woofer channel
      Lmix: L + 0.7071C + 0.7071LS
      Rmix: R + 0.7071C + 0.7071RS
      T: 0.7071C
      Q1: 0.7071LS + 0.7071RS
      Q2: 0.7071LS - 0.7071RS

      Table 2. Channel symbols for audio channels in DV video [4]



























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Authors' Addresses

   Katsushi Kobayashi
   Communication Research Laboratory
   4-2-1 Nukii-kita machi, Koganei
   Tokyo 184-8795 JAPAN

   Phone: [phone]
   EMail: [e-mail]


   Akimichi Ogawa
   Keio University
   5322 Endo, Fujisawa
   Kanagawa 252 JAPAN

   EMail:  [e-mail]


   Stephen L. Casner
   Packet Design
   2465 Latham Street
   Mountain View, CA 94040
   United States

   Phone: [phone]
   EMail: [e-mail]


   Carsten Bormann
   Universitaet Bremen TZI
   Postfach 330440
   D-28334 Bremen, Germany

   Phone: [phone]
   Fax:   [phone]
   EMail: [e-mail]














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Full Copyright Statement

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

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
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   The limited permissions granted above are perpetual and will not be
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Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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