Multichannel Publication using MPEG-21 DIDL and extensions

Steven Van Assche
Auguste Reyerslaan 52
Brussels, Belgium
Filip Hendrickx
Kapeldreef 75
Leuven, Belgium
Lode Nachtergaele
Kapeldreef 75
Leuven, Belgium


This poster discusses the multichannel publication of multimedia presentations using MPEG-21 DIDL and extensions. Different descriptions belonging to one MPEG-21 content item are combined and processed into a publication targeted at a specific channel and platform.


Multimedia, multichannel publication, device independent publishing, MPEG-21 DIDL


Nowadays, content creators are looking for ways to publish their content cost-efficiently in a multichannel environment, which means publishing content via multiple channels to various consumption platforms. This is only possible if the content (predominantly high quality audio-visual media in this example) is adapted to the specific target platforms, both from a technical (client capabilities, such as available downstream bandwidth and supported media formats) and a rhetorical viewpoint (the way the information is conveyed to the user). It is clear that content reuse is of prime importance when publishing in a multichannel environment. Ideally, all content is produced only once and straightforwardly converted to the appropriate formats for the target channels. This is called the ``create once, publish anywhere'' content production paradigm.

This poster demonstrates the use of MPEG-21 DIDL in multichannel publication. The generic hierarchical structure stimulates content reuse and extensibility. This is shown using an example.


The basic concept in the MPEG-21 DIDL model is the digital item, which is a structured digital object with its meta-data. Such an item is a grouping of sub-items and components that are bound to relevant descriptors. The descriptors contain information (meta-data) about the item. A component is the binding of a resource to a set of descriptors. The descriptors hold the information related to the specific resource instance. Examples of textual descriptors are descriptive, control, revision tracking or identifying information. A resource is an individually identifiable asset such as a video or audio clip, an image, or a textual asset. In our model we would call a resource a piece of essence.

Figure 1 shows an example MPEG-21 DIDL document. The document has a container with two items. There is one item holding two descriptors and two components. The components each have a resource and an asscociated descriptor and represent, for example, different compression quality versions of the same picture. The second item shows an item containing a sub-item.

Figure 1: The hierarchical structure of a MPEG-21 DIDL document. 1. Digital item with two components (for example, different quality versions) and two descriptors. 2. Digital item with a sub-item.

The MPEG-21 DIDL descriptor is a very generic concept, to which we add some more structure by attaching a version and type attribute. The version helps keep track of different versions or variants. It is a Uniform Resource Name (URN); the type attribute is free text. An example of a version attribute is www:xhtml1.1:2.0, which stands for a description variant for the web, using XHTML 1.1, and with running version 2.0. Example descriptor types are Layout and Synchronization. This extension is called XiMPF (eXtensible Interactive Multimedia Publication Format).


In order to demonstrate the multichannel publication capabilities, we elaborate on an example multichannel publication. We create a presentation of a photo album showing a series of pictures together with corresponding text. Figures 3,  4 and 5 show the MPEG-21 item with essence components and spatial or temporal positional descriptors.

Figure 2: SMIL (left), HTML-TIME (middle) and Java version (right) of the photo album.
Multichannel publication

Figure 3: Digital item representing an image. The item has two image versions: a PAL-version and a thumbnail version.
<Item id="photo_1">
  <Component ximpf:version="pal">
    <Resource ref="photo_1_720x576.jpg"/>
  <Component ximpf:version="thumbnail">
    <Resource ref="photo_1_100x80.jpg"/>

Figure 4: Synchronization descriptor of the sequential presentation. Each image will be shown during 5s.
  <Statement type="text/xml/smil-2.0">
      <ximpf:UseItem ximpf:referrer="img_1"
      <ximpf:UseItem ximpf:referrer="img_2"

Figure 5: Layout descriptor that adds a margin.
  <Statement type="text/css2">
    margin: 5px;

We then derive three final form presentations from the generic XiMPF description: a SMIL version, an HTML-TIME version and a Java version. Screenshots of these three publications are shown in Figure 2. The look and feel is the same in all three versions, except for the text in the SMIL version, because text in SMIL should be styled with another markup language.


The presented multichannel publication framework is based on MPEG-21 DIDL and some extensions. In the example, we demonstrated that the publication infrastructure is capable of handling multichannel publications. From the same content, publications were constructed for very different target platforms.


This work is a result of a joint collaboration between Vlaamse Radio en Televisie (VRT, public broadcaster of Flanders), IMEC and Vrije Universiteit Brussel (VUB). This is one of the E-VRT projects funded by the Flemish government.


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  3. Patrick Schmitz. Synchronized Multimedia Integration Language (SMIL) - HTML+SMIL Language Profile. W3C, jun 2000. Available at
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