The document discusses the implementation of the Media Fragments URI specification, which allows for the identification of media fragments such as video and images using URIs. It outlines requirements for temporal, spatial, track, and named fragments, and provides several recipes for processing these fragments effectively. Additionally, it mentions support for various user agents and servers, along with issues related to compatibility and rendering.

1. Implementing the Media
Fragments URI
Specification
Raphaël Troncy <raphael.troncy@eurecom.fr>,
Davy Van Deursen, Erik Mannens
Silvia Pfeiffer,
Yves Lafon

2. Use Case
 Aidem received on her Facebook
wall a status message containing a
Media Fragment URI
 Use a ‘#’ !
 Highlight a video
sequence
 Highlight a region
to pay attention to
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3. Media Fragments URI
Provide URI-based
mechanisms for uniquely
identifying fragments for
media objects on the Web,
such as video, audio, and
images.
Photo credit: Robert Freund
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4. Requirements
 r01: Temporal fragments:
 a clipping along the time dimension from a start to an end time that
are within the duration of the media resource
 r02: Spatial fragments:
 a clipping of an image region, only consider rectangular regions
 r03: Track fragments:
 a track as exposed by a container format of the media resource
 r04: Named fragments:
 a media fragment - either a track, a time section, or a spatial region -
that has been given a name through some sort of annotation
mechanism
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5. Side Conditions
 Restrict to what the container format (encapsulating the
compressed media content) can express (and expose),
thus no transcoding
 Protocol covered: HTTP(S), FILE, RTSP, RTMP
http://www.w3.org/TR/media-frags-reqs/
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6. Media Fragments processing
 General principle:
 Smart UA will strip out the fragment definition and
encode it into custom http headers ...
 (Media) Servers will handle the request, slice the media
content and serve just the fragment while old ones will
serve the whole resource
 Four recipes proposed
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7. Recipe 1: UA mapped byte ranges
 The User Agent knows how to map a custom unit into bytes and
sends a normal Range request expressed in bytes
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8. Recipe 1: UA mapped byte ranges
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9. Recipe 2: Server mapped byte ranges
 The UA sends a Range request expressed in a custom unit (e.g.
seconds), the server answers directly with a 206 Partial Content
and indicates the mapping between bytes and the custom unit
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10. Recipe 2: Server mapped byte ranges
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11. Recipe 3: Proxy cacheable variant
 The UA sends a Range request expressed in a custom unit (e.g.
seconds), the server answers first with just a Head and the
mapping between the custom unit and bytes so that the UA issues
another normal
Range request
expressed this
time in bytes
making the
answer
cacheable.
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12. Recipe 3: Proxy cacheable variant
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13. Recipe 4: Serving playable resources
 The UA sends a Range request expressed in a custom unit (e.g.
seconds), the server provides a multipart message body reply
(multipart/byte-ranges) containing not only the bytes
corresponding to requested media fragment but also the media
header data making the resource playable.
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14. Recipe 4: Serving playable resources
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15. Implementation
 Media Fragment server (4 recipes supported):
 Ninsuna: http://ninsuna.elis.ugent.be/MediaFragmentsServer
 Media Fragment user agents:
 Ninsuna Flash player:
http://ninsuna.elis.ugent.be/MediaFragmentsPlayer
Supports recipe 1
 Silvia Pfeiffer's experiment with HTML5 + JS:
http://annodex.net/~silvia/itext/mediafrag.html
Supports recipe 1 (for .ogg files and time dimension)
 Firefox pluggin
development in order to
support all recipes
(HTML5 +
XMLHttpRequest)
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16. Issues
 Communicating with the media player
 HTML5 browser: patch submitted for Firefox
 Flash: need to build a custom player
 Media Fragments rendering
 Spatial dimension?
 Names/Tracks discovery
 Media Multitrack (JS) API:
http://www.w3.org/WAI/PF/HTML/wiki/Media_MultitrackAPI
 Get involved?
http://www.w3.org/TR/media-frags/
http://lists.w3.org/Archives/Public/public-media-fragment/
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