[xiph-commits] r13846 - experimental/ivo/drafts
ivo at svn.xiph.org
ivo at svn.xiph.org
Sun Sep 16 17:55:35 PDT 2007
Author: ivo
Date: 2007-09-16 17:55:35 -0700 (Sun, 16 Sep 2007)
New Revision: 13846
Modified:
experimental/ivo/drafts/draft-xiph-rfc3534bis.txt
Log:
rewrote introduction; extended security considerations; specified what audio/ogg is for
Modified: experimental/ivo/drafts/draft-xiph-rfc3534bis.txt
===================================================================
--- experimental/ivo/drafts/draft-xiph-rfc3534bis.txt 2007-09-16 22:07:20 UTC (rev 13845)
+++ experimental/ivo/drafts/draft-xiph-rfc3534bis.txt 2007-09-17 00:55:35 UTC (rev 13846)
@@ -38,18 +38,33 @@
1. Introduction
- This memo describes media types for the Ogg container format.
- Refer to "Introduction" in [RFC3533] and "Overview" in [Ogg] for
- background information on this encapsulation format.
+ This memo describes media types for Ogg, a data encapsulation format
+ defined by the Xiph.Org Foundation. Refer to "Introduction" in
+ [RFC3533] and "Overview" in [Ogg] for background information on this
+ container format.
- Multimedia streams, such as Vorbis and Theora, have historically
- been interchanged using the application/ogg media type as defined by
- [RFC3534]. This document obsoletes [RFC3534] and defines three
- media types for different multimedia streams in Ogg to reflect this
- usage in the IANA media type registry, to foster interoperability by
- defining underspecified aspects, and to provide general security
- considerations.
+ Binary data contained in Ogg, such as Vorbis and Theora, has
+ historically been interchanged using the application/ogg media type
+ as defined by [RFC3534]. This document obsoletes [RFC3534] and
+ defines three media types for different multimedia streams in Ogg to
+ reflect this usage in the IANA media type registry, to foster
+ interoperability by defining underspecified aspects, and to provide
+ general security considerations.
+ The Ogg container format is known to contain Theora or Dirac video,
+ and Speex narrow-band speech, Speex wide-band speech, Vorbis or FLAC
+ audio. As Ogg encapsulates binary data, it is possible to include
+ any other type of video, audio, or text format.
+
+ While, raw packets from these codecs may be used directly by transport
+ mechanisms that provide their own framing and packet-separation
+ mechanisms (such as UDP datagrams or RTP), Ogg is a solution for
+ stream based storage (such as files) and transport (such as TCP
+ streams or pipes). The media types defined in this document are
+ needed to correctly identify such files when they are served over
+ HTTP, included in multi-part documents, or used in other places where
+ MIME [MIME1] types are used.
+
2. Conformance and Document Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
@@ -86,15 +101,26 @@
which are also defined in this document, are intended for common use
and should be used when dealing with video and/or audio content.
- Updates of this document may introduce optional parameters;
- implementations MUST consider the impact of such an update.
+ This registration applies to all files defined as using the Ogg
+ container format.
+ Although unlikely, ongoing work related to this registration may
+ introduce optional parameters in future revisions of this document.
+ One example area of effort may introduce a parameter that would
+ allow for codecs in use within the media type to be asserted and
+ determined without examination of the file. Implementations MUST
+ consider the impact of such an update.
+
X. Encoding Considerations
- Ogg encapsulated content is binary data, and must be encoded for
- non-binary transport; the base64 [RFC2397] encoding is suitable
- for EMail.
+ Ogg encapsulated content is binary data and should be transmitted in
+ a suitable encoding without CR/LF conversion, 7-bit stripping etc.;
+ base64 [RFC2397] is a suitable encoding.
+ Note that the media types described in this document are used only
+ for files; separate types are used for real-time transfer, such as
+ for the RTP payload formats for Theora video and Speex audio.
+
Note that most Ogg encapsulated content does not compress easily
using traditional lossless compression schemes.
@@ -103,16 +129,19 @@
Refer to [RFC3552] for a discussion of terminology used in this
section.
- 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.
+ The Ogg encapsulation format is a container and only a carrier of
+ content (such as audio, video, and displayable text data) with a
+ very rigid definition, this format in itself is not more vulnerable
+ than any other content framing mechanism.
+ Ogg 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 may be an issue with applications
that are implemented using Ogg, specifically when Ogg is used for
@@ -126,15 +155,27 @@
The requirement that such content not be executed on receipt
is especially important since situations exist where content
- will be generated independently and therefore could contain
+ will be generated independently and therefore might contain
executable content that the sender is unaware of.
- The "data" resource identifier scheme [RFC2397], in combination with
- the types defined in this document, might be used to cause execution
- of untrusted scripts through the inclusion of untrusted resource
- identifiers in otherwise trusted content. Security considerations of
- [RFC2397] apply.
+ It is possible to author malicious files, which attempt to call for
+ an excessively large picture size, high sampling-rate audio, etc.
+ Clients SHOULD protect themselves against this kind of attack.
+ It should be noted that selected metadata fields may encompass
+ information partly intended to protect the media against unauthorized
+ use or distribution. In this case, the intention is that alteration
+ or removal of the data in the field would be treated as an offense
+ under national agreements based on World Intellectual Property
+ Organization (WIPO) treaties.
+
+ Ogg has an extensible structure, so that it is theoretically
+ possible that metadata fields or media formats might be defined in
+ the future which might be used to induce particular actions on the
+ part of the recipient, thus presenting additional security risks.
+ However, this type of capability is currently not supported in the
+ referenced specification.
+
Implementations may fail to implement a specific security model or
other means to prevent possibly dangerous operations. Such failure
might possibly be exploited to gain unauthorized access to a system
@@ -145,12 +186,12 @@
The Ogg container format is device-, platform- and vendor-neutral
and has proved to be widely implementable across different computing
- platforms, including through a wide range of encoders and decoders.
- A broadly portable reference implementation [libogg] is available
- under a BSD license.
+ platforms, including a wide range of encoders and decoders. A broadly
+ portable reference implementation [libogg] is available under a BSD
+ license.
The Ogg container format is not patented and may be implemented by
- third parties without patent considerations.
+ third parties without intellectual property concerns.
The Xiph.Org Foundation has defined the specification,
interoperability, and conformance, and conducts regular
@@ -192,7 +233,7 @@
Macintosh File Type Code(s): OggS
- Person & email address to contact for further information:
+ Person & Email address to contact for further information:
See Author's Address section.
Intended usage: COMMON
@@ -200,27 +241,6 @@
Author: See Author's Address section.
Change controller: The Xiph.Org Foundation.
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7.2. video/ogg
Type name: video
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File extension(s): .ogv
Macintosh File Type Code(s): OggS
- Person & email address to contact for further information:
+ Person & Email address to contact for further information:
See Author's Address section.
Intended usage: COMMON
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Author: See Author's Address section.
Change controller: The Xiph.Org Foundation.
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7.3. audio/ogg
Type name: audio
@@ -292,6 +289,10 @@
Audio and video streaming and conferencing tools.
Additional information:
+ The type "audio/ogg" MAY be used for files containing audio
+ but no visual presentation. Files served under this type MUST
+ NOT contain any visual material. (Note that timed text is visually
+ presented and is considered to be visual material).
Magic number(s): The first four bytes, 0x4f 0x67 0x67
0x53, correspond to the string OggS.
@@ -307,7 +308,7 @@
Ogg MUST use the .oga file extension, even when multiplexed
with Vorbis or Speex-encoded audio.
- Person & email address to contact for further information:
+ Person & Email address to contact for further information:
See Author's Address section.
Intended usage: COMMON
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Author: See Author's Address section.
Change controller: The Xiph.Org Foundation.
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9. References
@@ -342,35 +323,13 @@
Author's Address
Ivo Emanuel Goncalves
- EMail: justivo at gmail.com
- URI: http://spreadopenmedia.org
+ Email: justivo at gmail.com
+ URI: xmpp:justivo at gmail.com
Note: Please write "Goncalves" with c-cedilla (U+00E7) wherever
possible, e.g., as "Ivo Emanuel Gonçalves" in HTML and XML.
Add your name here if you are contributing to this document.
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Full Copyright Statement
Copyright (C) The Internet Society (2007).
@@ -401,4 +360,4 @@
-Xiph.Org Foundation Informational [Page 15]
+Xiph.Org Foundation Informational [Page XX]
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