Annodex.net: Differentiators

Open standards for annotating and indexing networked media

We are often asked how the Annodex technologies differ from other media standards. Here are a set of answers.

1. How does the CMWeb technology differ from SMIL?

SMIL is for authoring interactive multimedia presentations while Annodex is for providing Web searching and Web hyperlinking capabilities for clips of video or audio. SMIL does not integrate the media data for its presentation in one streamable file, but just references them from within the XML file. This also means that SMIL presentations cannot be cached by a Web proxy, while Annodex streams can. A recorded SMIL interaction can however be annodexed and made available for searching and surfing.

2. How does the CMWeb technology differ from MPEG-21?

MPEG-21 is building an open framework for multimedia delivery and consumption. It thus focuses on addressing how to generically describe a set of content documents (called a "digital item") that belong together from a semantic point of view, including all the information necessary to provide services on these digital items. As an example, consider a music CD album. When it is turned into a "digital item", the album gets described in an XML document that contains references to the cover image, the text on the CD cover, the text on an accompagnying brochure, references to a set of audio files that contain the songs on the CD, ratings of the album, rights associated with the album, information on the different encoding formats in which the music can be retrieved, different bitrates that can be supported when downloading etc. This description supports everything that you would want to do with a digital CD album: it allows you to manage it as an entity, describe it with meta data, exchange it with others, and collect it as an entity.

In comparison, the CMWeb is focusing on a much smaller task. It looks only at time-continuous data files, it allows to create meta information for clips of that data file, and it allows to incorporate this meta information in a time-synchronous manner into the bitstream. Its only aim is to integrate time-continuous data files into the existing World Wide Web by making clips accessible through URIs and searchable through textual search engines. So, the music CD example would be represented in the CMWeb as one large audio file on a Web server that consists of a concatenation of the songs of that album and has some XML markup interspersed into it at the relevant points where a new song starts. There will be textual meta information in the bitstream that describes the different songs allowing them to be searched through a Web search engine. This is considered as one Web resource. There may be hyperlinks in that file to other Web resources that represent the cover image and the accompagnying brochure, but they are not part of the Web resource. Therefore, it is not possible to describe the kind of entity that is represented in an MPEG-21 digital item through the CMWeb. But by focusing squarely on time-continuous data files only, by providing a markup language that is similar to HTML, by enabling the time-synchronous storage of that markup in the media bitstream and by extending the URI linking scheme to address clips of time-continuous data files, we can leverage of existing Web infrastructure. We expect that Annodex media will become part of the formats that MPEG-21 digital items can hold.

3. How does the CMWeb technology differ from MPEG-7?

MPEG-7 is an open framework for describing multimedia content. It provides a large set of description schemes to create markup in XML format. MPEG-7's markup is not restricted to textual information only - in fact it is tailored to allow for the description of audio-visual content with low-level image and audio features as extracted through signal processing methods. It also has basically no resemblance to HTML as it was not built with a particular aim on Web applications only.

Instead, the CMWeb technology provides for a HTML-like textual markup of time-continuous data files in its markup language CMML. It provides for an inclusion of its markup into the time-continuous data stream in its Annodex file format, which is not provided for in MPEG-7. It provides for the URI addressing of clips of time-continuous data files through an extension of the URI fragment addressing scheme. However, annotations created in MPEG-7 may be referenced from inside an Annodex format bitstream, and some may even be included directly into the CMML of an Annodex format bitstream through the "meta" and "desc" tags.

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