rfc3533.txt

mediastreamer2是开源的网络传输媒体流的库

      frames encoded after this page.  This is a hint for the decoder
      and gives it some timing and position information.  Its meaning is
      dependent on the codec for that logical bitstream and specified in
      a specific media mapping.  A special value of -1 (in two's
      complement) indicates that no packets finish on this page.

   5. bitstream_serial_number: a 4 Byte field containing the unique
      serial number by which the logical bitstream is identified.

   6. page_sequence_number: a 4 Byte field containing the sequence
      number of the page so the decoder can identify page loss.  This
      sequence number is increasing on each logical bitstream
      separately.

   7. CRC_checksum: a 4 Byte field containing a 32 bit CRC checksum of
      the page (including header with zero CRC field and page content).
      The generator polynomial is 0x04c11db7.

   8. number_page_segments: 1 Byte giving the number of segment entries
      encoded in the segment table.

   9. segment_table: number_page_segments Bytes containing the lacing
      values of all segments in this page.  Each Byte contains one
      lacing value.

   The total header size in bytes is given by:
   header_size = number_page_segments + 27 [Byte]

   The total page size in Bytes is given by:
   page_size = header_size + sum(lacing_values: 1..number_page_segments)
   [Byte]

7. Security Considerations

   The Ogg encapsulation format is a container format and only
   encapsulates content (such as Vorbis-encoded audio).  It does not
   provide for any generic encryption or signing of itself or its
   contained content bitstreams.  However, it encapsulates any kind of
   content bitstream as long as there is a codec for it, and is thus
   able to contain encrypted and signed content data.  It is also
   possible to add an external security mechanism that encrypts or signs
   an Ogg physical bitstream and thus provides content confidentiality
   and authenticity.

   As Ogg encapsulates binary data, it is possible to include executable
   content in an Ogg bitstream.  This can be an issue with applications
   that are implemented using the Ogg format, especially when Ogg is
   used for streaming or file transfer in a networking scenario.  As



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   such, Ogg does not pose a threat there.  However, an application
   decoding Ogg and its encapsulated content bitstreams has to ensure
   correct handling of manipulated bitstreams, of buffer overflows and
   the like.

8. References

   [1] Walleij, L., "The application/ogg Media Type", RFC 3534, May
       2003.

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







































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Appendix A. Glossary of terms and abbreviations

   bos page: The initial page (beginning of stream) of a logical
      bitstream which contains information to identify the codec type
      and other decoding-relevant information.

   chaining (or sequential multiplexing): Concatenation of two or more
      complete physical Ogg bitstreams.

   eos page: The final page (end of stream) of a logical bitstream.

   granule position: An increasing position number for a specific
      logical bitstream stored in the page header.  Its meaning is
      dependent on the codec for that logical bitstream and specified in
      a specific media mapping.

   grouping (or concurrent multiplexing): Interleaving of pages of
      several logical bitstreams into one complete physical Ogg
      bitstream under the restriction that all bos pages of all grouped
      logical bitstreams MUST appear before any data pages.

   lacing value: An entry in the segment table of a page header
      representing the size of the related segment.

   logical bitstream: A sequence of bits being the result of an encoded
      media stream.

   media mapping: A specific use of the Ogg encapsulation format
      together with a specific (set of) codec(s).

   (Ogg) packet: A subpart of a logical bitstream that is created by the
      encoder for that bitstream and represents a meaningful entity for
      the encoder, but only a sequence of bits to the Ogg encapsulation.

   (Ogg) page: A physical bitstream consists of a sequence of Ogg pages
      containing data of one logical bitstream only.  It usually
      contains a group of contiguous segments of one packet only, but
      sometimes packets are too large and need to be split over several
      pages.

   physical (Ogg) bitstream: The sequence of bits resulting from an Ogg
      encapsulation of one or several logical bitstreams.  It consists
      of a sequence of pages from the logical bitstreams with the
      restriction that the pages of one logical bitstream MUST come in
      their correct temporal order.






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   (Ogg) segment: The Ogg encapsulation process splits each packet into
      chunks of 255 bytes plus a last fractional chunk of less than 255
      bytes.  These chunks are called segments.

Appendix B. Acknowledgements

   The author gratefully acknowledges the work that Christopher
   Montgomery  and the Xiph.Org foundation have done in defining the Ogg
   multimedia project and as part of it the open file format described
   in this document.  The author hopes that providing this document to
   the Internet community will help in promoting the Ogg multimedia
   project at http://www.xiph.org/.  Many thanks also for the many
   technical and typo corrections that C. Montgomery and the Ogg
   community provided as feedback to this RFC.

Author's Address

   Silvia Pfeiffer
   CSIRO, Australia
   Locked Bag 17
   North Ryde, NSW  2113
   Australia

   Phone: [phone]
   EMail: [e-mail]
   URI:   http://www.cmis.csiro.au/Silvia.Pfeiffer/

























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Full Copyright Statement

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

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Acknowledgement

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



















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