Implementing the Media Fragments URI Specification

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

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -2

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -3

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -4

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/ 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -5

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -6

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -7

Recipe 1: UA mapped byte ranges 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -8

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 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA -9

Recipe 2: Server mapped byte ranges 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 10

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. 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 11

Recipe 3: Proxy cacheable variant 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 12

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. 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 13

Recipe 4: Serving playable resources 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 14

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) 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 15

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/ 29/04/2010 - Implementing the Media Fragments URI Specification - WWW 2010, Raleigh, USA - 16

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Implementing the Media Fragments URI Specification

by Raphael Troncy

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