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<h1>W3C Video on the Web Workshop <span class="baseline">12-13 December 2007, San Jose, California and Brussels, Belgium</span></h1>
</div>
<div id="navigation">
<ul>
<li><a href="http://www.w3.org/Consortium/">About W3C</a></li>
<li><a href="/2007/08/video/">Call for Participation</a></li>
<li><a href="papers">Papers</a></li>
<li class='current'>Report</li>
<li><a href="agenda">Agenda</a></li>
</ul>
</div>
<div id="main">
<p class="logo" style="float:right;margin-left:1em;"><a href="/"><img src="/Icons/WWW/w3c_home_nb" alt="W3C" height="48" width="72" /></a></p>
<h2 id="report" style="clear:left;">Workshop Report</h2>
<!-- content beg -->

<div class='report'> <p>W3C organized a workshop on Video on the Web
in December 2007, hosted by Cisco Systems, in order to share current
experiences and examine the technologies. <a href='papers.html'>42
position papers</a> were submitted for the Workshop and <a href='minutes.html'>37
organizations</a> attended the event from a wide range of applications:
content producers, network companies, research institutes, hardware
vendors, video platforms, browser vendors, users, etc. The meeting was
hosted in San Jose, California and Brussels, Belgium, with both
locations linked with high definition video.</p>

<div class="subtoc">
<h3>Table of Contents</h3>
<ol>
  <li><a href="#Summary">Summary</a></li>
  <li><a href="#Introduction">Introduction</a></li>
  <li><a href="#Metadata">Metadata</a></li>
  <li><a href="#Video_codec_for_the_Web">Video codec for the Web</a></li>
  <li><a href="#Deep_linking_into_Video_content">Addressing into Video
    content</a>
    <ol>
      <li><a href="#Temporal_Addressing">Temporal Addressing</a></li>
      <li><a href="#Spatial_Addressing">Spatial Addressing</a></li>
    </ol>
  </li>
  <li><a href="#DRM">Digital Rights Management</a></li>
  <li><a href="#Other_Topics">Other Topics of Interest</a>
    <ol>
      <li><a href="#Accessibility">Accessibility</a></li>
      <li><a href="#HTML_video_tag">HTML <code>video</code> tag</a></li>
      <li><a href="#API">APIs for Controlling Video</a></li>
      <li><a href="#Content_Delivery">Content Delivery and Network
      Traffic</a></li>
    </ol>
  </li>
  <li><a href="#Next_steps">Next steps</a>
  <ol>
    <li><a href='#step1'>8.1 Codecs and containers</a></li>
    <li><a href='#step2'>8.2 Metadata</a></li>
    <li><a href='#step3'>8.3 Addressing</a></li>
    <li><a href='#step5'>8.4 Best practices for video and audio content</a></li>
    <li><a href='#step4'>8.5 Cross-group coordination</a></li>
  </ol>
  </li>
</ol>
</div>

<h2 id="Summary">1. Summary</h2>

<div class="image noprint">
<p class="img" style="width: 274px"><a href='http://www.flickr.com/photos/rwfreund/2115753881/'><img src="/2008/01/camera.jpg" title="Camera"
alt="Camera" /></a>
<br />
<span class="source">Photo credit: <a
href="http://www.flickr.com/photos/rwfreund/">Bob Freund</a></span></p>
</div>

<p>Online video content and demand is increasing rapidly and the trend will
continue for at least a few years. Workshop participants gathered to discuss
and to share current experiences and to examine the technologies. Some of the
key issues participants discussed related to:</p>
<ul>
  <li><strong>Metadata</strong>: searching and discovering video is difficult
    with the volume of online video. Having <em>data about data</em>, whether those are
    automatically generated or manually added, is important, especially when
    considering the value added by metadata provided by users.</li>
  <li><strong>Video codec</strong>: several W3C Working Groups are struggling
    with the issue of recommending a baseline video codec for the World Wide
    Web. W3C should continue to investigate the existing video codecs.</li>
  <li><strong>Addressing</strong>: in order to make video a first-class
    object on the World Wide Web, one should be able to identify spatial and
    temporal clips. Having global identifiers for clips would allow
    substantial benefits, including in linking, bookmarking, caching and
    indexing. None of the existing solutions is fully satisfactory or
    provides a unique resource identifier for clips.</li>
  <li><strong>Content protection</strong>: many content producers feel that
    the success of video online is tied to the ability to manage digital
    rights associated with the media. While W3C will not investigate the
    issue of enforcement, it should look into metadata for digital
  rights.</li>
</ul>

<p>The Workshop was informative and energetic, and it is anticipated that the
W3C Team will work with the Membership to propose a new W3C Activity to
continue studying video on the Web, including, for example, Guidelines for
publishing and deploying online video.</p>

<h2 id="Introduction">2. Introduction</h2>

<div class="image noprint">
<p class="img" style="width: 167px"><a href='http://www.flickr.com/photos/roessler/2109755736/'><img src="/2008/01/chris_takes_a_picture_2.jpg"
alt="W3C Video Workshop Telepresence" title="W3C Video Workshop Telepresence"
/></a>
<br />
<span class="source">Photo credit: <a
href="http://www.flickr.com/photos/49504282@N00/">Chris Lilley</a></span></p>
</div>

<p>Online video has become omnipresent on the Web in the recent years.
YouTube, launched in 2005, represented 4% of traffic on high-Internet lines
on the Comcast network by the end of 2006. Online video appeals to the Web
audience as it lets people go beyond the capabilities of traditional
television: more people can distribute video ("the long tail") and social
networking allows others in the community to comment, and even reply with
other video. The number of user generated video uploads per day is expected
to go from 500,000 in 2007 to 4,800,000 in 2011 (<a href='http://www.ripcode.com/prodForm.php'><cite>Transcoding Internet and Mobile Video: Solutions for the Long Tail</cite></a>, IDC, September 2007). The demand for
online video content also keeps increasing. Recent studies indicate that the
number of U.S. internet users who have visited a video-sharing site increased
by 45% in 2007, and the daily traffic to such sites has doubled (<a
href="http://www.pewinternet.org/PPF/r/232/report_display.asp"><cite>PEW Internet Project Data Memo</cite></a>, PEW/Internet, January 2008).
Expectations are quickly evolving to the point where people want videos to
publish and view at any time and from any device. These rapid changes are
posing challenges to the underlying technologies and standards that support
the platform-independent creation, authoring, encoding/decoding, and
description of video. To ensure the success of video as a "first class
citizen" of the Web, the community needs to build a solid architectural
foundation that enables people to create, navigate, search, and distribute
video, and to manage digital rights.</p>

<p>W3C has been involved in the area of Video on the Web since 1996,
and organized two workshops around this in the past: <cite><a
href="http://www.w3.org/AudioVideo/RTMW96.html">Real Time Multimedia
and the Web</a></cite> (October 1996) and <cite><a
href="http://www.w3.org/Architecture/1998/06/Workshop/">Television and
the Web</a></cite> (June 1998). SMIL (Synchronized Multimedia
Integration Language), first published in June 1998, provides support
for embedding audio and video content. W3C continues to work on the
integration of video with other media, synchronized video content in
graphics with SVG (Scalable Vector Graphics), and direct support for
video and audio in Web browsers with the proposal for a video element
in HTML 5.</p>

<h2 id="Metadata">3. Metadata</h2>

<p>Workshop participants expressed great interest on the subject of
metadata for video and audio content. This was the topic that
generated the most discussion and interest at the Workshop, with use
cases coming from several perspectives.  The major use cases for
adding metadata were content labeling, search, and
discovery. Anticipating the increase in online video and audio in the
upcoming years, participants observed that it will become
proportionally more difficult for viewers to find the content. It was
noted that metadata comes from several places: content creator,
publisher, third-party, or users. Some of the metadata will be
automatically produced (face, text or object recognition) and others
will be manually added. Some of the metadata will be part of the
content (in the format container) or external to the content. Adding
user-generated metadata can increase tremendously the value of the
content.  Of course, the quality of such metadata will highly vary,
especially in non-trusted environments. There was a wide range of
interest for adding specific metadata: title, author, year, cast,
city, digital rights, ratings, tagging, etc. It was pointed out that
multiple video formats can be available for the same video, at
different data rates. Also, the availability of the metadata will
depend on the delivery chain and the player used. For example,
transcoding often means that the metadata will get dropped.</p>

<p>Several more or less complex solutions exist in this domain: MPEG 7, SMIL,
iTunes XML, Yahoo! MediaRSS, CableLabs VOD Metadata Content, etc. Not many
online video distributors are making use of metadata or facilitating the use
of by others, either in the professional world or in the world of user
generated video. Despite the general interest in metadata, no clear direction
came from the workshop. Given its Semantic Web activity, the W3C should
continue to investigate in this area, while taking into account the existing
solutions.</p>

<h2 id="Video_codec_for_the_Web">4. Video codec for the Web</h2>

<div class="image noprint">
<p class="img"><img src="/2008/01/video-container_2.png"
title="Format container and codecs" alt="Format container and codecs" />
</p>
</div>

<p>The issue of video codec has been around for a few years — for example,
the SMIL 3 specification attempts to recommend a baseline video codec based on SMIL 1 and 2
experience — but surfaced more preeminently in relation to HTML 5. The <a
href="http://www.w3.org/TR/html5/">HTML 5 Working Draft</a>, which includes a
proposal for embedding and controlling <a
href="http://www.w3.org/TR/2008/WD-html5-20080122/#audio">audio</a> and <a
href="http://www.w3.org/TR/2008/WD-html5-20080122/#video">video</a> content,
has attracted a lot of attention on the choice of video codec. The HTML
Working Group seems inclined to recommend a baseline video codec, there is
not yet consensus on which codec to recommend. The Group has elaborated a
number of requirements, such as <q>compatibility with the open source
development model</q> or <q>no additional submarine patent risk</q> (see
section 3.14.7.1, <cite><a
href="http://www.w3.org/TR/2008/WD-html5-20080122/#video0">Video and audio
codecs for video elements</a></cite>, HTML 5), some of which may be
incompatible.</p>
<!-- forward reference to thml video tag section -->

<p>Several existing video codecs were discussed by the Workshop
participants. H.264 has been adopted a lot of the industry. The mobile
industry has adopted H.264, at least in 3GPP/3GPP2 standards. Adobe
recently announced support for H.264 in their Flash product. However,
the H.264 has licensing requirements that are incompatible with open
source requirements and is not a royalty-free codec (which makes it
incompatible with the <a
href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Licensing">goals</a>
of the W3C Patent Policy). Until recently, the HTML 5 specification
was indicating that browser implementations suggested that browser
implementations support the Theora codec. There are currently
uncertainties about the IPR requirements surrounding the Theora codec,
and organizations are concerned about taking additional submarine
patent risks. Of course, one can claim that not all risks are known
for the H.264 video codec either. It should also be noted that several
patents around these video technologies expire every year. Other codec
candidates to consider are Dirac, VC-1, or older codecs such as H.261
or H.263. Video codecs keep evolving and today's codec will be
different from tomorrow's codec. The BBC submitted the intra-only
portion of Dirac (“Dirac 1.0.0”) to SMPTE and it is expected to become a
standard in the upcoming few months, as “VC-2”. BBC claims that it is
<a href='http://dirac.sourceforge.net/specification.html'>suitable for
professional applications</a>. The BBC also released the full version
of Dirac (“Dirac 2.1.0”) on 24 January 2008, which includes motion
compensation and is <a
href='http://dirac.sourceforge.net/specification.html'>suitable for
broadcasting and streaming</a>. The Joint Video Team (JVT) of ISO/ITU
released a scalable profile of H.264 in the spring last year and
started the work on H.265.</p>

<p>For large video content producers, the end user experience is more
important than the goal of a single baseline codec. The end user experience
includes widely available players, codecs whose functionality provides a good
viewing experience, and other issues related to ease of use. Most will take
Flash Video for granted in fact, or will deploy their own video player, using
a codec that fits the desired quality of the content (such as the VP7 On2
codec). Individual content producers — the home video crowd — still
suffer from the lack of a universally supported set of codecs, which makes it
challenging to publish video on the Web and to be sure that almost anyone can
view it in commonly available browsers. One should be able to publish a video
the same way one publishes an image nowadays. The sentiment shared among
several participants was that W3C should gather the relevant parties and
continue to explore the issue. The participants of the Workshop did not
discuss issues associated with audio codecs, mostly due to the predominant
concerns with video codecs. Analogous audio codec issues also merit
investigation.</p>

<h2 id="Deep_linking_into_Video_content">5. Addressing into Video content</h2>

<p>In order to make video and audio real first-class objects on the
Web, one should be able to link from and to media, the same way
authors can make hyperlinks between Web pages. It also allows other
use cases, such as video highlights, search results, mashing, or
caching. It also provides an identifier that can then be reused to
attach metadata. The discussion covered spatial and temporal
addressing, as well as a combination of the two.</p>

<h3 id="Temporal_Addressing">5.1 Temporal Addressing</h3>

<div class="image noprint">
<p class="img"><img src="/2008/01/timbl_movie_2.png" title="Movie tape"
alt="Movie tape" />
</p>
</div>

<p>Temporal addressing provides the ability to reference a time point,
or a segment of time, in video and audio content: a normal play time
(or time offset), a framed-based time, or an absolute time.  It allows
the media player to jump to the specified time or frame, or only to
play a segment of file. RFC 2326 (RTSP) defines the notion of normal
play time, the stream absolute position relative to the beginning of
the video. SMPTE time codes (SMPTE 12M-1999 Television, Audio and Film
— Time and Control Code) defines the notion of frame-level
accuracy. Absolute time uses UTC.</p>

<p>Temporal addressing approaches in <a
href="http://www.w3.org/TR/SMIL/">SMIL</a>, <a
href="http://www.chiariglione.org/mpeg/standards/mpeg-7/mpeg-7.htm">MPEG-7</a>,
<a
href="http://www.chiariglione.org/mpeg/standards/mpeg-21/mpeg-21.htm">MPEG-21</a>
and <a
href="http://www.annodex.net/TR/draft-pfeiffer-temporal-fragments-03.html">temporal
URI</a>.</p>

<p>Both SMIL and MPEG-7 require an indirection: one needs to get the
XML description containing the temporal information before fetching
the video content. It should be noted, thought it was not mentioned at
the Workshop, that even HTML 5 includes the notion of time offset and
time segment.</p>

<p>On the other hand, the MPEG-21 and Temporal URI approaches rely on
defining a URI syntax and thus don't rely on an additional XML description.
However, these approaches also have limitations:</p>
<ul>
  <li><p>They lack the ability to represent complex fragments, especially
    when combining temporal and spatial addressing.</p>
  </li>
  <li><p>When using the fragment identifier component syntax of a URI, it is
    dependent on the media type of the retrieved representation (see section
    3.5, Fragment, RFC 3986). For example, the MPEG-21 URI syntax is tied to
    the MPEG container. Thus, it would be difficult to apply one generic
    fragment identifier to the existing video or audio codecs.</p>
  </li>
</ul>

<h3 id="Spatial_Addressing">5.2 Spatial Addressing</h3>

<div class="image noprint">
<p class="img" style="width: 250px"><a href='http://www.flickr.com/photos/rwfreund/2116534410/'><img src="/2008/01/beth_2.jpg"
title="Beth, the audience, Belgium, her pitch, and herself"
alt="Beth, the audience, Belgium, her pitch, and herself" /></a>
<br />
<span class="source">Photo credit: <a
href="http://www.flickr.com/photos/rwfreund/">Bob Freund</a></span></p>
</div>

<p>Spatial addressing provides the ability to reference a region in a video
frame. Information can then be attached to the particular region or, when
combined with timed-based addressing, objects can then be tracked in the
video.</p>

<p>Three solutions were mentioned at the workshop: SVG, SMIL and
MPEG-7. All solutions require an indirection for accessing the region
in the video.</p>

<h2 id="DRM">6. Digital Rights Management</h2>

<p>Several of the participants at the Workshop were interested in the topic
of Digital Rights management, an issue particularly important in the music
and the motion picture and television industries. This topic touched on two
subjects mentioned above: video codec and metadata. A baseline video codec
and format container for online video content would only satisfy some of the
content producers if it is associated with a digital rights management (DRM)
solution. No one suggested that W3C should develop a DRM system but future work
at W3C needs to keep DRM issues in mind. It was noted that the choice of
video codec doesn't need to be tied to the choice of DRM system, since both
technologies are independent in general. There was also some interest in
investigating further the area of metadata for digital rights (copyright and
licensing).</p>

<h2 id="Other_Topics">7. Other Topics of Interest</h2>

<p>Other topics of interest listed in this section were mentioned or
discussed at the workshop.</p>

<h3 id="Accessibility">7.1 Accessibility</h3>

<p>W3C has a mission to ensure that the Web is accessible to people
with disabilities; naturally this includes video content. A vast
majority of online video and non-professional content lacks
captioning, sign language, or video description. The Web Content
Accessibility Guidelines 1.0 were published in May 1999 and there are
several solutions for captioning/video description currently
available. Extensions have been made to support captioning using the
W3C Timed Text (DXFP) format in combination with the Flash player, but
DXFP itself is not yet a W3C Recommendation. The Flash Player 9
adopted 3GPP TS 26.245 as its Timed Text format. SMIL 3.0 introduced
SMILText, which can also be used to captioning/subtitling.</p>

<h3 id="HTML_video_tag">7.2 HTML <code>video</code> tag</h3>

<p>The HTML <code>video</code> tag was mentioned several times during the
Workshop. The primary focus of the discussion was around the baseline video
codec but several participants were concerned with the introduction of
yet-another-tag for embedding and controlling video content, especially since
the SYMM Working Group has already published a specification that addresses
timing and synchronization. The HTML Working Group introduced the notion of
cue range in their specification and care should be taken to ensure the
compatibility between the two models. No in-depth discussion happened at the
Workshop on this issue and the best recommendation at this time is to ensure
that the SYMM and HTML Working Groups coordinate their actions.</p>

<h3 id="API">7.3 APIs for Controlling Video</h3>

<p>The control of video content using APIs was a use case in several
presentations and the . Both SMIL and HTML specifications are
providing solutions to start, stop, or pause a video. Work is still
happening in the HTML specification to extend the media API. A more
extended API, the <a
href='http://wiki.xiph.org/index.php/OggPlayJavascriptAPI'>draft
API</a> for the Ogg Play Firefox plugin, was presented at the
workshop. </p>

<h3 id="Content_Delivery">7.4 Content Delivery and Network Traffic</h3>

<p>The major issue of delivering video content over the Internet and the Web
is network traffic scalability. While it's easy to deploy a Web server to
deliver HTML pages and images, video content and its bandwidth requirements
introduced an entirely new dimension. Progressive HTTP, Content Delivery
Networks, streaming media servers, or P2P technologies are among the
solutions with different cost of deployment and bandwidth. P2P technologies
have a significant impact on the network of existing ISPs, forcing them to
rethink the way they allocate the bandwidth among their users.</p>

<h2 id="Next_steps">8. Next steps</h2>

<p>
  Five major areas of possible work emerged from the Workshop (the
  first three discussed in detail): video codecs, metadata,
  addressing, cross-group coordination and best practices for video
  content.
</p>

<h3 id='step1'>8.1 Codecs and containers</h3>

<p>
The W3C team will work with interested parties to evaluate
the situation with regards to video codecs, and what, if anything, W3C
can do to ensure that codecs, containers, etc. for the Web encourage
the broadest possible adoption and interoperability.
</p>

<h3 id='step2'>8.2 Metadata</h3>

<p>Talks at the Workshop highlighted a number of metadata standards in
the space (and the number is part of the problem).  Still, there was
high interest in this area. One direction would be to create a Working Group
tasked to come up with:</p>
<ol>
<li>a <em>simple</em> common ontology between the existing standards;</li>
<li>defines a mapping between this ontology and existing
standards;</li>
<li>defines a roadmap for extending the ontology, including information
related to copyright and licensing rights.</li>
</ol>

<h3 id='step3'>8.3 Addressing</h3>

<p>W3C should also consider creating a Group to investigate the
important issue of addressing. The goal would be to:</p>
<ol>
<li>provide a URI syntax for temporal and spatial addressing;</li>
<li>investigate how to attach metadata information to spatial and
temporal regions when using RDF or other existing specifications, such
as SMIL or SVG.</li>
</ol>

<h3 id='step5'>8.4 Best practices for video and audio content</h3>

<p>A Group working on guidelines and best practices for effective
video and audio content on the Web could be useful, and would look at
the entire existing delivery chain from producers to end-users, from
content delivery, to metadata management, accessibility or device
independence.</p>

<h3 id='step4'>8.5 Cross-group coordination</h3>

<p>Several existing W3C Working Groups are working on video-related
issues and there is a need for coordination (controls, layouts,
etc.):</p>
<ol>
<li>Video and CSS (layout and layering);</li>
<li>Video and SMIL, SVG or HTML (effects, transforms, codecs, playback, API);</li>
<li>Video and WAI (accessibility)</li>
<li>Video and browsers and plugins (for device independence and
managing plug-n-play specialized codecs that match various end-user
experience needs within the browser)</li>
</ol>

</div>

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<div id="footer">
<address>For more information, contact <span class="vcard"><a class="url fn" href="http://www.w3.org/People/LeHegaret/">Philippe Le Hégaret</a>, W3C Contact</span><br />
<small>$Date: 2008/04/08 20:43:53 $</small></address>
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