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RTCWEB D. Burnett
Internet-Draft Voxeo
Intended status: Standards Track April 23, 2012
Expires: October 23, 2012
IANA Registry for RTCWeb Media Constraints
draft-burnett-rtcweb-constraints-registry-01
Abstract
Specifications in W3C's Media Capture Task Force and WebRTC Working
Group have need of a registry in which to maintain a list of HTML
Media constraints. This document defines this registry.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 23, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (http://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 2
3.1. RTCWeb Media Constraints . . . . . . . . . . . . . . . . . 2
3.1.1. Designated Expert Instructions . . . . . . . . . . . . 3
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4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
There are two W3C specifications that have need of a registry in
which to represent constraints: getusermedia: Getting access to local
devices that can generate multimedia streams [W3C.WD-getusermedia-
2012xxxx] and WebRTC 1.0: Real-time Communication Between Browsers
[W3C.WD-webrtc-20120209]. In the former, the getUserMedia() method
on the NavigatorUserMedia interface takes an "options" argument
(which may be renamed "constraints"). In the latter, the addMedia()
method on the PeerConnection interface takes a "hints" parameter
(soon to be renamed "constraints"). Both of these parameters make use
of a data structure representing a list of constraints on the HTML
media or media connection to be established. Additionally, both
specifications also (will soon) define getCapabilities() methods that
are used to query the web browser about its capabilities. The
returned data structure specifies the browser's capabilities in terms
of constraints that it can satisfy. The data structures and their
use are defined in the aforementioned specifications. This document
specifies the registry used to define individual constraint names,
their allowed values, and their meanings.
2. Requirements Language
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 [RFC2119].
3. IANA Considerations
This document defines a registry "RTCWeb Media Constraints" for use
by W3C specifications needing to indicate constraints on HTML Media,
both as used by web application authors to indicate preferences and
as used by web browsers to indicate constraints they can satisfy.
3.1. RTCWeb Media Constraints
IANA SHALL create a new name space of "RTCWeb Media Constraints".
All maintenance within and additions to the contents of this name
space MUST be according to the "Specification Required with Expert
Review" registration policy as defined in RFC5226 [RFC5226]. The
registry is initially empty. The registry is defined in the
remainder of this section.
Each registry entry consists of a Name and a Reference (or list of
references).
An RTCWeb Media Constraint Name MUST satisfy the following ABNF
[RFC5234] specification:
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rtcweb-media-constraint = media-type constraint-type constraint
media-type = "audio" / "video"
constraint-type = "Min" / "Max" / "Enum"
constraint = %x41-5A 0*constraint-char
constraint-char = ALPHA / DIGIT
Constraint names are case-sensitive.
A registration request MUST include the following information:
o The constraint name to be registered
o Name and Email address of a contact person for the registration
o Organization or individuals having the change control
o Reference(s) to the specification(s) defining the constraint
3.1.1. Designated Expert Instructions
Constraint names are of unlimited length according to the syntax.
However, it is RECOMMENDED that they be no longer than 80 characters
in total. This is to keep them reasonable for humans to read and
use.
A constraint name with media-type of "audio" MUST be relevant to
audio media streams and connections. A constraint of media-type
"video" MUST be relevant to video media streams and connections.
A constraint MUST satisfy the following criteria based upon its
constraint-type:
min
When used by a web application author, the constraint MUST
represent the minimum value the author is willing to accept.
When returned by a web browser as a capability, the constraint
MUST represent the minimum value that the web browser could
satisfy if requested to by the web application author. The
constraint specification MUST clearly define the units
associated with the value if the value itself does not specify
them.
max
When used by a web application author, the constraint MUST
represent the maximum value the author is willing to accept.
When returned by a web browser as a capability, the constraint
MUST represent the maximum value that the web browser could
satisfy if requested to by the web application author. The
constraint specification MUST clearly define the units
associated with the value if the value itself does not specify
them.
enum
The constraint specification MUST enumerate all allowed values.
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The constraint MUST be well enough defined in the specification that
it is understandable by implementors and application developers that
will use the constraint. The constraint SHOULD NOT duplicate a
condition that can be achieved using constraints already defined in
the registry. The constraint name SHOULD be appropriate and specific
enough for the constraint.
4. Security Considerations
Since the constraints envisioned for this registry are fairly generic
in nature, it is not expected that the mere existence of this
registry will introduce any particular security issues. Any
specification defining one or more new constraints SHOULD address any
specific security issues that might be introduced by the
constraint(s).
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
5.2. Informative References
[W3C.WD-webrtc-20120209]
Bergkvist, A., Burnett, D., Jennings, C. and A. Narayanan,
"WebRTC 1.0: Real-Time Communication Between Browsers",
World Wide Web Consortium WD WD-webrtc-20120209, February
2012, <http://www.w3.org/TR/2012/WD-webrtc-20120209>.
[W3C.WD-getusermedia-2012xxxx]
Burnett, D. and A. Narayanan, "getusermedia: Getting
access to local devices that can generate multimedia
streams", World Wide Web Consortium WD WD-getusermedia-
2012xxxx, XXX 2012, <http://www.w3.org/TR/2012/WD-
getusermedia-2012xxxx>.
Appendix A. Acknowledgements
The authors would like to thank the members of the W3C Media Capture
Task Force and WebRTC Working Group, the members of the IETF RTCWEB
Working Group, and the people who gave specific early review and
feedback: Cullen Jennings and Travis Leithead.
Author's Address
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Daniel C. Burnett
Voxeo
189 South Orange Avenue #1000
Orlando, FL 32801
USA
Email: dburnett@voxeo.com
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