Restrict 'width' and 'height' to the 0..65535 range, instead of being unbounded integers. This is in accordance to XEP-0084 and XEP-0221 for instance.
0.4.12022-09-05lnj
Update xmlns in schema (was not updated when bumping)
0.42015-08-26ljts
Changed format to use generic 'uri' attribute to allow for 'https:' and 'http:' URIs in addition to BoB 'cid:' URIs.
Indicated that multiple thumbnails may be present.
Expanded scope of use cases to be Jingle content in general, not just file transfer.
0.32009-04-27ml
Fixed typo in author's name :).
0.22009-04-06ml
Add paragraph in security section about protecting against malicious thumbnail dimensions in offer. Fixed a typo.
0.12009-04-02psa
Initial published version.
0.0.32009-03-10ml
Split use-case section into "Introduction", "Requirements", and "Use case".
0.0.22009-02-25ml
Removed service disovery.
Added missing namespace on thumnail elements.
0.0.12009-02-23ml
First draft.
When offering a Jingle session, it can be helpful to provide a small preview of the offered content to help the session responder decide whether to accept or reject the session.
This is particularly useful for file transfer content (especially image files), but can also be used for things such as video (e.g. using a still frame from the stream as the preview thumbnail), and even audio by using a small image of album cover art.
This documents defines a way to include a thumbnail image as an additional metadata in a Jingle content description.
When a client wishes to supply a thumbnail in a content offer, it can do so by including an extra <thumbnail/> element as shown in the following example:
image/jpeg
image.jpg3032449552da749930852c69ae5d2141d3766b1This is a test. If this were a real file...
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Thumbnails MAY be included for Jingle content other than file transfer. For example, with Jingle RTP video a thumbnail could be included to show who is calling (either by capturing a still frame from the input stream or by using an existing profile image):
128
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Multiple <thumbnail/> elements MAY be included to provide thumbnails of different sizes, media types, or URIs.
If the provided URI has the scheme 'cid', then the thumbnail data MAY be requested using Bits of Binary (XEP-0231)XEP-0231: Bits of Binary <https://xmpp.org/extensions/xep-0231.html>..
The following attributes are defined for the <thumbnail/> element.
Attribute
Description
Inclusion
uri
A URI where the thumbnail data can be accessed (typically by using a URI scheme of 'cid:', 'https:', or 'http:'). If the URI scheme is 'cid:' then the identifier MUST refer to a bit of binary data as described in Bits of Binary (XEP-0231)XEP-0231: Bits of Binary <https://xmpp.org/extensions/xep-0231.html>.
REQUIRED
media-type
The value of the 'media-type' attribute MUST match the syntax specified in RFC 2045RFC 2045: Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies <http://tools.ietf.org/html/rfc2045>.. That is, the value MUST include a top-level media type, the "/" character, and a subtype; in addition, it MAY include one or more optional parameters. The "type/subtype" string SHOULD be registered in the IANA MIME Media Types RegistryIANA registry of MIME media types <http://www.iana.org/assignments/media-types>., but MAY be an unregistered or yet-to-be-registered value.
RECOMMENDED
width
The intended display width of the thumbnail image. Used as a hint for the receiving client to prepare the appropriate UI, such as a dialog window.
OPTIONAL
height
The intended display height of the thumbnail image. Used as a hint for the receiving client to prepare the appropriate UI, such as a dialog window.
OPTIONAL
The inclusion of an image thumbnail may leak information about a transfer
otherwise taking place on an e2e encrypted file transfer stream. A client MAY
wish to not include a thumbnail.
A client MUST NOT rely on the values specified for the width and height of a thumbnail to allocate a bitmap data buffer for the thumbnail, to prevent possible DoS attacks. Also a client SHOULD apply implementation-specific limits on the thumbnails, if using these values to pepare a UI element for the thumbnail image, e.g. with dimensions of 128x128 pixels, values exceeding these would then be truncated and the thumbnail image scaled down when received.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA)The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>..
This specification defines the following XML namespace:
urn:xmpp:thumbs:1
The XMPP RegistrarThe XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>. includes this namespace in the registry located at <https://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function (XEP-0053)XEP-0053: XMPP Registrar Function <https://xmpp.org/extensions/xep-0053.html>..
If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.
The protocol documented by this schema is defined in
XEP-0264: http://www.xmpp.org/extensions/xep-0264.html
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