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+Network Working Group S. Pfeiffer
+Request for Comments: 3533 CSIRO
+Category: Informational May 2003
+
+
+ The Ogg Encapsulation Format Version 0
+
+Status of this Memo
+
+ This memo provides information for the Internet community. It does
+ not specify an Internet standard of any kind. Distribution of this
+ memo is unlimited.
+
+Copyright Notice
+
+ Copyright (C) The Internet Society (2003). All Rights Reserved.
+
+Abstract
+
+ This document describes the Ogg bitstream format version 0, which is
+ a general, freely-available encapsulation format for media streams.
+ It is able to encapsulate any kind and number of video and audio
+ encoding formats as well as other data streams in a single bitstream.
+
+Terminology
+
+ 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 BCP 14, RFC 2119 [2].
+
+Table of Contents
+
+ 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 2
+ 3. Requirements for a generic encapsulation format . . . . . . . 3
+ 4. The Ogg bitstream format . . . . . . . . . . . . . . . . . . . 3
+ 5. The encapsulation process . . . . . . . . . . . . . . . . . . 6
+ 6. The Ogg page format . . . . . . . . . . . . . . . . . . . . . 9
+ 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
+ 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
+ A. Glossary of terms and abbreviations . . . . . . . . . . . . . 13
+ B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
+ Author's Address . . . . . . . . . . . . . . . . . . . . . . . 14
+ Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15
+
+
+
+
+
+
+
+Pfeiffer Informational [Page 1]
+
+RFC 3533 OGG May 2003
+
+
+1. Introduction
+
+ The Ogg bitstream format has been developed as a part of a larger
+ project aimed at creating a set of components for the coding and
+ decoding of multimedia content (codecs) which are to be freely
+ available and freely re-implementable, both in software and in
+ hardware for the computing community at large, including the Internet
+ community. It is the intention of the Ogg developers represented by
+ Xiph.Org that it be usable without intellectual property concerns.
+
+ This document describes the Ogg bitstream format and how to use it to
+ encapsulate one or several media bitstreams created by one or several
+ encoders. The Ogg transport bitstream is designed to provide
+ framing, error protection and seeking structure for higher-level
+ codec streams that consist of raw, unencapsulated data packets, such
+ as the Vorbis audio codec or the upcoming Tarkin and Theora video
+ codecs. It is capable of interleaving different binary media and
+ other time-continuous data streams that are prepared by an encoder as
+ a sequence of data packets. Ogg provides enough information to
+ properly separate data back into such encoder created data packets at
+ the original packet boundaries without relying on decoding to find
+ packet boundaries.
+
+ Please note that the MIME type application/ogg has been registered
+ with the IANA [1].
+
+2. Definitions
+
+ For describing the Ogg encapsulation process, a set of terms will be
+ used whose meaning needs to be well understood. Therefore, some of
+ the most fundamental terms are defined now before we start with the
+ description of the requirements for a generic media stream
+ encapsulation format, the process of encapsulation, and the concrete
+ format of the Ogg bitstream. See the Appendix for a more complete
+ glossary.
+
+ The result of an Ogg encapsulation is called the "Physical (Ogg)
+ Bitstream". It encapsulates one or several encoder-created
+ bitstreams, which are called "Logical Bitstreams". A logical
+ bitstream, provided to the Ogg encapsulation process, has a
+ structure, i.e., it is split up into a sequence of so-called
+ "Packets". The packets are created by the encoder of that logical
+ bitstream and represent meaningful entities for that encoder only
+ (e.g., an uncompressed stream may use video frames as packets). They
+ do not contain boundary information - strung together they appear to
+ be streams of random bytes with no landmarks.
+
+
+
+
+
+Pfeiffer Informational [Page 2]
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+RFC 3533 OGG May 2003
+
+
+ Please note that the term "packet" is not used in this document to
+ signify entities for transport over a network.
+
+3. Requirements for a generic encapsulation format
+
+ The design idea behind Ogg was to provide a generic, linear media
+ transport format to enable both file-based storage and stream-based
+ transmission of one or several interleaved media streams independent
+ of the encoding format of the media data. Such an encapsulation
+ format needs to provide:
+
+ o framing for logical bitstreams.
+
+ o interleaving of different logical bitstreams.
+
+ o detection of corruption.
+
+ o recapture after a parsing error.
+
+ o position landmarks for direct random access of arbitrary positions
+ in the bitstream.
+
+ o streaming capability (i.e., no seeking is needed to build a 100%
+ complete bitstream).
+
+ o small overhead (i.e., use no more than approximately 1-2% of
+ bitstream bandwidth for packet boundary marking, high-level
+ framing, sync and seeking).
+
+ o simplicity to enable fast parsing.
+
+ o simple concatenation mechanism of several physical bitstreams.
+
+ All of these design considerations have been taken into consideration
+ for Ogg. Ogg supports framing and interleaving of logical
+ bitstreams, seeking landmarks, detection of corruption, and stream
+ resynchronisation after a parsing error with no more than
+ approximately 1-2% overhead. It is a generic framework to perform
+ encapsulation of time-continuous bitstreams. It does not know any
+ specifics about the codec data that it encapsulates and is thus
+ independent of any media codec.
+
+4. The Ogg bitstream format
+
+ A physical Ogg bitstream consists of multiple logical bitstreams
+ interleaved in so-called "Pages". Whole pages are taken in order
+ from multiple logical bitstreams multiplexed at the page level. The
+ logical bitstreams are identified by a unique serial number in the
+
+
+
+Pfeiffer Informational [Page 3]
+
+RFC 3533 OGG May 2003
+
+
+ header of each page of the physical bitstream. This unique serial
+ number is created randomly and does not have any connection to the
+ content or encoder of the logical bitstream it represents. Pages of
+ all logical bitstreams are concurrently interleaved, but they need
+ not be in a regular order - they are only required to be consecutive
+ within the logical bitstream. Ogg demultiplexing reconstructs the
+ original logical bitstreams from the physical bitstream by taking the
+ pages in order from the physical bitstream and redirecting them into
+ the appropriate logical decoding entity.
+
+ Each Ogg page contains only one type of data as it belongs to one
+ logical bitstream only. Pages are of variable size and have a page
+ header containing encapsulation and error recovery information. Each
+ logical bitstream in a physical Ogg bitstream starts with a special
+ start page (bos=beginning of stream) and ends with a special page
+ (eos=end of stream).
+
+ The bos page contains information to uniquely identify the codec type
+ and MAY contain information to set up the decoding process. The bos
+ page SHOULD also contain information about the encoded media - for
+ example, for audio, it should contain the sample rate and number of
+ channels. By convention, the first bytes of the bos page contain
+ magic data that uniquely identifies the required codec. It is the
+ responsibility of anyone fielding a new codec to make sure it is
+ possible to reliably distinguish his/her codec from all other codecs
+ in use. There is no fixed way to detect the end of the codec-
+ identifying marker. The format of the bos page is dependent on the
+ codec and therefore MUST be given in the encapsulation specification
+ of that logical bitstream type. Ogg also allows but does not require
+ secondary header packets after the bos page for logical bitstreams
+ and these must also precede any data packets in any logical
+ bitstream. These subsequent header packets are framed into an
+ integral number of pages, which will not contain any data packets.
+ So, a physical bitstream begins with the bos pages of all logical
+ bitstreams containing one initial header packet per page, followed by
+ the subsidiary header packets of all streams, followed by pages
+ containing data packets.
+
+ The encapsulation specification for one or more logical bitstreams is
+ called a "media mapping". An example for a media mapping is "Ogg
+ Vorbis", which uses the Ogg framework to encapsulate Vorbis-encoded
+ audio data for stream-based storage (such as files) and transport
+ (such as TCP streams or pipes). Ogg Vorbis provides the name and
+ revision of the Vorbis codec, the audio rate and the audio quality on
+ the Ogg Vorbis bos page. It also uses two additional header pages
+ per logical bitstream. The Ogg Vorbis bos page starts with the byte
+ 0x01, followed by "vorbis" (a total of 7 bytes of identifier).
+
+
+
+
+Pfeiffer Informational [Page 4]
+
+RFC 3533 OGG May 2003
+
+
+ Ogg knows two types of multiplexing: concurrent multiplexing (so-
+ called "Grouping") and sequential multiplexing (so-called
+ "Chaining"). Grouping defines how to interleave several logical
+ bitstreams page-wise in the same physical bitstream. Grouping is for
+ example needed for interleaving a video stream with several
+ synchronised audio tracks using different codecs in different logical
+ bitstreams. Chaining on the other hand, is defined to provide a
+ simple mechanism to concatenate physical Ogg bitstreams, as is often
+ needed for streaming applications.
+
+ In grouping, all bos pages of all logical bitstreams MUST appear
+ together at the beginning of the Ogg bitstream. The media mapping
+ specifies the order of the initial pages. For example, the grouping
+ of a specific Ogg video and Ogg audio bitstream may specify that the
+ physical bitstream MUST begin with the bos page of the logical video
+ bitstream, followed by the bos page of the audio bitstream. Unlike
+ bos pages, eos pages for the logical bitstreams need not all occur
+ contiguously. Eos pages may be 'nil' pages, that is, pages
+ containing no content but simply a page header with position
+ information and the eos flag set in the page header. Each grouped
+ logical bitstream MUST have a unique serial number within the scope
+ of the physical bitstream.
+
+ In chaining, complete logical bitstreams are concatenated. The
+ bitstreams do not overlap, i.e., the eos page of a given logical
+ bitstream is immediately followed by the bos page of the next. Each
+ chained logical bitstream MUST have a unique serial number within the
+ scope of the physical bitstream.
+
+ It is possible to consecutively chain groups of concurrently
+ multiplexed bitstreams. The groups, when unchained, MUST stand on
+ their own as a valid concurrently multiplexed bitstream. The
+ following diagram shows a schematic example of such a physical
+ bitstream that obeys all the rules of both grouped and chained
+ multiplexed bitstreams.
+
+ physical bitstream with pages of
+ different logical bitstreams grouped and chained
+ -------------------------------------------------------------
+ |*A*|*B*|*C*|A|A|C|B|A|B|#A#|C|...|B|C|#B#|#C#|*D*|D|...|#D#|
+ -------------------------------------------------------------
+ bos bos bos eos eos eos bos eos
+
+ In this example, there are two chained physical bitstreams, the first
+ of which is a grouped stream of three logical bitstreams A, B, and C.
+ The second physical bitstream is chained after the end of the grouped
+ bitstream, which ends after the last eos page of all its grouped
+ logical bitstreams. As can be seen, grouped bitstreams begin
+
+
+
+Pfeiffer Informational [Page 5]
+
+RFC 3533 OGG May 2003
+
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+ together - all of the bos pages MUST appear before any data pages.
+ It can also be seen that pages of concurrently multiplexed bitstreams
+ need not conform to a regular order. And it can be seen that a
+ grouped bitstream can end long before the other bitstreams in the
+ group end.
+
+ Ogg does not know any specifics about the codec data except that each
+ logical bitstream belongs to a different codec, the data from the
+ codec comes in order and has position markers (so-called "Granule
+ positions"). Ogg does not have a concept of 'time': it only knows
+ about sequentially increasing, unitless position markers. An
+ application can only get temporal information through higher layers
+ which have access to the codec APIs to assign and convert granule
+ positions or time.
+
+ A specific definition of a media mapping using Ogg may put further
+ constraints on its specific use of the Ogg bitstream format. For
+ example, a specific media mapping may require that all the eos pages
+ for all grouped bitstreams need to appear in direct sequence. An
+ example for a media mapping is the specification of "Ogg Vorbis".
+ Another example is the upcoming "Ogg Theora" specification which
+ encapsulates Theora-encoded video data and usually comes multiplexed
+ with a Vorbis stream for an Ogg containing synchronised audio and
+ video. As Ogg does not specify temporal relationships between the
+ encapsulated concurrently multiplexed bitstreams, the temporal
+ synchronisation between the audio and video stream will be specified
+ in this media mapping. To enable streaming, pages from various
+ logical bitstreams will typically be interleaved in chronological
+ order.
+
+5. The encapsulation process
+
+ The process of multiplexing different logical bitstreams happens at
+ the level of pages as described above. The bitstreams provided by
+ encoders are however handed over to Ogg as so-called "Packets" with
+ packet boundaries dependent on the encoding format. The process of
+ encapsulating packets into pages will be described now.
+
+ From Ogg's perspective, packets can be of any arbitrary size. A
+ specific media mapping will define how to group or break up packets
+ from a specific media encoder. As Ogg pages have a maximum size of
+ about 64 kBytes, sometimes a packet has to be distributed over
+ several pages. To simplify that process, Ogg divides each packet
+ into 255 byte long chunks plus a final shorter chunk. These chunks
+ are called "Ogg Segments". They are only a logical construct and do
+ not have a header for themselves.
+
+
+
+
+
+Pfeiffer Informational [Page 6]
+
+RFC 3533 OGG May 2003
+
+
+ A group of contiguous segments is wrapped into a variable length page
+ preceded by a header. A segment table in the page header tells about
+ the "Lacing values" (sizes) of the segments included in the page. A
+ flag in the page header tells whether a page contains a packet
+ continued from a previous page. Note that a lacing value of 255
+ implies that a second lacing value follows in the packet, and a value
+ of less than 255 marks the end of the packet after that many
+ additional bytes. A packet of 255 bytes (or a multiple of 255 bytes)
+ is terminated by a lacing value of 0. Note also that a 'nil' (zero
+ length) packet is not an error; it consists of nothing more than a
+ lacing value of zero in the header.
+
+ The encoding is optimized for speed and the expected case of the
+ majority of packets being between 50 and 200 bytes large. This is a
+ design justification rather than a recommendation. This encoding
+ both avoids imposing a maximum packet size as well as imposing
+ minimum overhead on small packets. In contrast, e.g., simply using
+ two bytes at the head of every packet and having a max packet size of
+ 32 kBytes would always penalize small packets (< 255 bytes, the
+ typical case) with twice the segmentation overhead. Using the lacing
+ values as suggested, small packets see the minimum possible byte-
+ aligned overhead (1 byte) and large packets (>512 bytes) see a fairly
+ constant ~0.5% overhead on encoding space.
+
+
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+Pfeiffer Informational [Page 7]
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+RFC 3533 OGG May 2003
+
+
+ The following diagram shows a schematic example of a media mapping
+ using Ogg and grouped logical bitstreams:
+
+ logical bitstream with packet boundaries
+ -----------------------------------------------------------------
+ > | packet_1 | packet_2 | packet_3 | <
+ -----------------------------------------------------------------
+
+ |segmentation (logically only)
+ v
+
+ packet_1 (5 segments) packet_2 (4 segs) p_3 (2 segs)
+ ------------------------------ -------------------- ------------
+ .. |seg_1|seg_2|seg_3|seg_4|s_5 | |seg_1|seg_2|seg_3|| |seg_1|s_2 | ..
+ ------------------------------ -------------------- ------------
+
+ | page encapsulation
+ v
+
+ page_1 (packet_1 data) page_2 (pket_1 data) page_3 (packet_2 data)
+------------------------ ---------------- ------------------------
+|H|------------------- | |H|----------- | |H|------------------- |
+|D||seg_1|seg_2|seg_3| | |D|seg_4|s_5 | | |D||seg_1|seg_2|seg_3| | ...
+|R|------------------- | |R|----------- | |R|------------------- |
+------------------------ ---------------- ------------------------
+
+ |
+pages of |
+other --------| |
+logical -------
+bitstreams | MUX |
+ -------
+ |
+ v
+
+ page_1 page_2 page_3
+ ------ ------ ------- ----- -------
+ ... || | || | || | || | || | ...
+ ------ ------ ------- ----- -------
+ physical Ogg bitstream
+
+ In this example we take a snapshot of the encapsulation process of
+ one logical bitstream. We can see part of that bitstream's
+ subdivision into packets as provided by the codec. The Ogg
+ encapsulation process chops up the packets into segments. The
+ packets in this example are rather large such that packet_1 is split
+ into 5 segments - 4 segments with 255 bytes and a final smaller one.
+ Packet_2 is split into 4 segments - 3 segments with 255 bytes and a
+
+
+
+Pfeiffer Informational [Page 8]
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+RFC 3533 OGG May 2003
+
+
+ final very small one - and packet_3 is split into two segments. The
+ encapsulation process then creates pages, which are quite small in
+ this example. Page_1 consists of the first three segments of
+ packet_1, page_2 contains the remaining 2 segments from packet_1, and
+ page_3 contains the first three pages of packet_2. Finally, this
+ logical bitstream is multiplexed into a physical Ogg bitstream with
+ pages of other logical bitstreams.
+
+6. The Ogg page format
+
+ A physical Ogg bitstream consists of a sequence of concatenated
+ pages. Pages are of variable size, usually 4-8 kB, maximum 65307
+ bytes. A page header contains all the information needed to
+ demultiplex the logical bitstreams out of the physical bitstream and
+ to perform basic error recovery and landmarks for seeking. Each page
+ is a self-contained entity such that the page decode mechanism can
+ recognize, verify, and handle single pages at a time without
+ requiring the overall bitstream.
+
+ The Ogg page header has the following format:
+
+ 0 1 2 3
+ 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1| Byte
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| capture_pattern: Magic number for page start "OggS" | 0-3
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| version | header_type | granule_position | 4-7
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| | 8-11
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| | bitstream_serial_number | 12-15
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| | page_sequence_number | 16-19
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| | CRC_checksum | 20-23
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| |page_segments | segment_table | 24-27
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+| ... | 28-
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+
+ The LSb (least significant bit) comes first in the Bytes. Fields
+ with more than one byte length are encoded LSB (least significant
+ byte) first.
+
+
+
+
+
+
+
+Pfeiffer Informational [Page 9]
+
+RFC 3533 OGG May 2003
+
+
+ The fields in the page header have the following meaning:
+
+ 1. capture_pattern: a 4 Byte field that signifies the beginning of a
+ page. It contains the magic numbers:
+
+ 0x4f 'O'
+
+ 0x67 'g'
+
+ 0x67 'g'
+
+ 0x53 'S'
+
+ It helps a decoder to find the page boundaries and regain
+ synchronisation after parsing a corrupted stream. Once the
+ capture pattern is found, the decoder verifies page sync and
+ integrity by computing and comparing the checksum.
+
+ 2. stream_structure_version: 1 Byte signifying the version number of
+ the Ogg file format used in this stream (this document specifies
+ version 0).
+
+ 3. header_type_flag: the bits in this 1 Byte field identify the
+ specific type of this page.
+
+ * bit 0x01
+
+ set: page contains data of a packet continued from the previous
+ page
+
+ unset: page contains a fresh packet
+
+ * bit 0x02
+
+ set: this is the first page of a logical bitstream (bos)
+
+ unset: this page is not a first page
+
+ * bit 0x04
+
+ set: this is the last page of a logical bitstream (eos)
+
+ unset: this page is not a last page
+
+ 4. granule_position: an 8 Byte field containing position information.
+ For example, for an audio stream, it MAY contain the total number
+ of PCM samples encoded after including all frames finished on this
+ page. For a video stream it MAY contain the total number of video
+
+
+
+Pfeiffer Informational [Page 10]
+
+RFC 3533 OGG May 2003
+
+
+ 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
+
+
+
+Pfeiffer Informational [Page 11]
+
+RFC 3533 OGG May 2003
+
+
+ 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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+Pfeiffer Informational [Page 12]
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+RFC 3533 OGG May 2003
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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.
+
+
+
+
+
+
+Pfeiffer Informational [Page 13]
+
+RFC 3533 OGG May 2003
+
+
+ (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: +61 2 9325 3141
+ EMail: Silvia.Pfeiffer@csiro.au
+ URI: http://www.cmis.csiro.au/Silvia.Pfeiffer/
+
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+Pfeiffer Informational [Page 14]
+
+RFC 3533 OGG May 2003
+
+
+Full Copyright Statement
+
+ Copyright (C) The Internet Society (2003). 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
+ kind, provided that the above copyright notice and this paragraph are
+ included on all such copies and derivative works. However, this
+ document itself may not be modified in any way, such as by removing
+ the copyright notice or references to the Internet Society or other
+ Internet organizations, except as needed for the purpose of
+ developing Internet standards in which case the procedures for
+ copyrights defined in the Internet Standards process must be
+ followed, or as required to translate it into languages other than
+ English.
+
+ The limited permissions granted above are perpetual and will not be
+ revoked by the Internet Society or its successors or assigns.
+
+ This document and the information contained herein is provided on an
+ "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
+ TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
+ BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
+ HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
+ MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Acknowledgement
+
+ Funding for the RFC Editor function is currently provided by the
+ Internet Society.
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+Pfeiffer Informational [Page 15]
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