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Motivation

Hyperlinking to time offsets: The temporal URI specification W3C Video Workshop Silvia Pfeiffer Dec 2007 Annodex Association, Xiph.Org, Vquence. Motivation. Hyperlinking to video offsets or segments directly (“deep hyperlinking”) Without transferring irrelevant part of resource Use cases:

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Motivation

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  1. Hyperlinking to time offsets: The temporal URI specificationW3C Video WorkshopSilvia PfeifferDec 2007Annodex Association, Xiph.Org, Vquence

  2. Motivation • Hyperlinking to video offsets or segments directly (“deep hyperlinking”) • Without transferring irrelevant part of resource • Use cases: • Playlists of video highlights (e.g. news bulletin) • Search results • Mashups without touching/changing original • Caching Web proxies

  3. Temporal URI examples • Time offset addressing: http://www.foo.bar/video.anx?t=85.28 • Time segment addressing: http://www.foo.bar/video.anx?t=85.28/102.20 • Named event addressing: http://www.foo.bar/video.anx?id=wedding

  4. Deep Hyperlinking • Difference to indirect hyperlinking through XPointer in a XML description container (e.g. MPEG-7, SMIL, MPEG-21) • Method of WWW: URIs (RFC 3986)

  5. Restrictions of RFC 3986 • http://www.ietf.org/rfc/rfc3986.txt • “… any operation associated with a URI reference is defined by the protocol element, data format attribute, or natural language text in which it appears.” • Want to use http • Data offset operation is data format specific

  6. Types of Addressing • Addressing a time offset • Addressing a time segment • Adressing a named event Keep them uniform

  7. What format? • “making use of a URI in order to retrieve a representation of its associated resource” foo://example.com:8042/over/there?name=ferret#nose \_/ \______________/\_________/ \_________/ \__/ | | | | | scheme authority path query fragment • Query or fragment to specify subcomponent

  8. Query or Fragment? • Fragment: “indirect identification of a secondary resource” • Query: “serves to identify a resource” • “Fragment identifiers have a special role in information retrieval systems as the primary form of client-side indirect referencing, allowing an author to specifically identify aspects of an existing resource that are only indirectly provided by the resource owner.” • I.e. fragments are resolved on client-side only

  9. Temporal URI spec • Use both: fragment and query • Semantics: • Fragment: client-side offsets / filtering • Query: server-side resource composition • Specific data format: Annodex files (ogg + skeleton + cmml)

  10. Annodex • Ogg files: Ogg is container format • Skeleton: logical bitstream that identifies contained tracks • CMML: annotation track that names sections

  11. Temporal URI examples • Time offset addressing: http://www.foo.bar/video.anx?t=85.28http://www.foo.bar/video.anx#t=85.28 • Time segment addressing: http://www.foo.bar/video.anx?t=85.28/102.20http://www.foo.bar/video.anx#t=85.28/102.20 • Named event addressing: http://www.foo.bar/video.anx?id=weddinghttp://www.foo.bar/video.anx#id=wedding

  12. Time specs in URI queries Accessing a time interval of an Annodex file: • temporal URI query parameter (CGI conformant) t=[time-scheme:]time-interval • http://www.foo.bar/csiro.anx?t=85.28 • http://www.foo.bar/csiro.anx?t=smpte-25:00:01:25:07 • http://www.foo.bar/csiro.anx?t=npt:85.28-105/290-300 • http://www.foo.bar/csiro.anx?t=clock:20040114T153045.25Z

  13. Annodex Web server Web Client ANX ANX URI URI Web Server http://www.foo.bar/fish.anx?t=7

  14. Time query processing Annodex file on server http://www.foo.bar/fish.anx?t=7 * retain BOS pages * retain secondary header pages * copy active clip tags * retain EOS pages

  15. Annodex Server Module • MIME types: application/annodex • Apache module: mod_annodex • module provides temporal and clip URI query handling by recomposing valid ANX resource

  16. Caching Web Proxy fish.anx?id=clip2 fish.anx?id=clip3 Caching Web Proxy fish.anx?id=clip1 ANX 2 3 Origin Web Server fish.anx?id=clip1

  17. Caching Web Proxy Caching Web Proxy ANX clip1 clip2 Origin Web Server clip3 fish.anx

  18. Summary • Challenges to address: • Get syntax right • Definition is data format specific • Semantics on server • Other implications on Web infrastructure

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