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Representing Internet Streaming Media Metadata using MPEG-7 Multimedia Description Schemes Eric Rehm Singingfish.com 18 West Mercer Street, Suite 300 Seattle, Washington 98119 1 (206) 691-0565

rehm @sin_clinqfish.com searchable schema for an implementation Corporations' eXcelon [4] X M L data server.

ABSTRACT Singingfish.com uses MPEG-7 description schemes to model the metadata characteristics of lnternet streaming media. Further it has used MPEG-7 description schemes as the basis for a number of internal experiments, processes, as well as interchange with commercial content partners. This paper describes our selection of description schemes from the MPEG-7 Multimedia Description Schemes (MDS) Working Drafts, their ability (or lack thereof) to represent Internet streaming media metadata, and our experiences (successes and failures) in using MPEG-7 DS's in various applications critical to building an Internet streaming media search engine.

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A later version of MPEG-7 MDS working draft [5] was used as the logical data model for lnternet streaming media and drove our initial RDBMS schema development. Currently, the main roles for the MPEG-7 MDS in our technology continue as the "guiding" data model lbr our RDBMS schemas and as the adapter schema for third party multimedia content metadata delivery. This paper is organized as follows: in section 2 we describe related work. In section 3 we describe what are the requirements to stream most audiovisual media in a web environment. In the subsections we describe in detail the different types of information we found essential to effectively describe streaming media and identify which description schemes in MPEG-7 best capture this information. As a result of our work we found that some description schemes needed to be extended (Section 4). We present the extensions we adopted and consequently proposed to the MPEG-7 standardization effort. Section 5 describes our implementations and finally section 6 presents our conclusions.

Keywords MPEG-7, streaming media, multimedia, and search engine.

1. INTRODUCTION In the Fall of 1999, Singingfish.com, an lnternet startup company in Seattle, Washington, began the construction and population of a searchable database of Internet streaming media. The database is available via a full-text search interface to Internet portals, destination sites and other Internet properties that purchase access.

2. RELATED WORK There has been significant development of MPEG-7 experimental model (XM) [22] by researchers involved with the MPEG-7 standard process. The author is aware of any publication describing the use of MPEG-7 Multimedia Description Schemes outside the MPEG-7 standard development process in a commercial application. So far a few research labs are using MPEG-7 to create proof of concept demos, (e.g., a demonstration by Sharp on MPEG-7 video summaries) but to our knowledge these efforts are not currently available as a product or used in real commercial applications.

lnternet streaming media, from our perspective, includes any multimedia data type where playback can begin before a download completes. This includes not only streaming via protocols such as HTTP [1] and RTP/RTSP [2], but also HTI'P file transfers at bit rates sufficient to keep pace with playback. Currently, the Singingfish.com database contains links to Microsoft Windows Media Formats, Apple QuickTime, MP3, and the following RealNetworks formats: RealVideo, RealAudio and RealFlash. Support for Macromedia Flash4 [23] and ActiveSky [24] are under development.

3. STREAMING AV DS

A prototype used portions of an early MPEG-7 MDS working draft [3] (in the form of an XML DTD) as the data model and

The Streaming AV Description Scheme (StreamingAV DS) is our top-level entity and describes a piece of Internet-accessible streaming multimedia content.

Pem~ission to make digital or hard copies of all or part of this work tbr personal or classroom use is granted without tee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. ACM Multimedia Workshop Marina Del Rey CA USA Copyright ACM 2000 1-58113-311-1/00/11...$5.00

Originally, the Multimedia Descriptions Group of MPEG-7 created a top-level entity called the "Generic AV DS"[6] to describe the visual as well as the audio content o f a single A V document. Guided by this Generic AV DS, we set out to describe the content of an Internet streaming media object (see Figure 1).

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S M I L : The SMIL implementation from RealNetworks [8] allows you to manage the player "frame" spatially via tiling (no overlap) and temporally (overlap between spatially distinct subsegments, but no temporal overlap within a spatial subsegment or "region"). A SMIL element (e.g., , tags) may reference other SMIL objects. In general, we only are concerned with the "main" presentation (audio or video with audio), and we currently only form a single level SegmentDecomposition. Future development plans include decoding spatially distinct RealText elements ( tag) into a TextSegment. Such text is often relevant to the audiovisual content.



ASX: Microsoft Windows Media metafiles allow you to represent a single level temporal decomposition. [9]

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M3U/PLS: These are popular MP3 audio playlist formats that simply list the U R L ' s of such MP3 audio files. We model these as a single level temporal SegmentDecomposition with subsegments without gap or overlap.

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Figure 1. Streaming AV Description Scheme We round that at least the following data and relationships had to be modeled:

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Overall Structure: single content item, playlist, SMIL [7] authored content, etc.

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Media Information: URL link(s) to stream, bit rate, media tormat (e.g., RealMedia, Windows Media, QuickTime), duration, MIME type, media type (audio, video, animation), etc.

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Creation Information: Title, Author, Copyright, Artist, Album, Record label, Language, etc.

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Classification: Category, and Genre. Categories are the root nodes of our taxonomy. Genre represents a path from a root node using a controlled vocabulary.

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Related Material: Referring page URL(s), title, anchor text, HTML meta tags (e.g., description, keywords)

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Usage Information: Copyright, Content Owner

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Spoken Text: Transcript from speech recognition

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Summary Information: Key frame(s)

A Segment DS is actually an abstract class. Subclasses of the Segment DS, the VideoSegment, AudioSegment, and TextSegment DS's were designed to contain information about the audio, video, and text in an AV content item.

3.2 Media Information The MPEG-7 Medialnformation DS contains descriptions that are specific to the storage m e d i a . . The Media Information DS contains one or more Media Profile DS's. !"'~,.~,o~;~,r;'-i

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The MPEG-7 Segment DS and Segment Decomposition DS allow us to model any hierarchical playlist format we have encountered on the lntemet.

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Each Media Profile represents one of possibly many variations that can be produced from a master media depending of the values chosen for the coding, storage format, etc. Intemet streaming media content is often encoded in more than one commercial format (RealMedia, Windows Media, QuickTime), each at several distinct bit rates, with each variation at a separate URL. We encode the commercial format with the Media Format's System element.

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If two identical instances of a particular stream exist on the Internet (quite common with MP3s), they can be simply represented with multiple Medialnstance descriptions.

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Overall, we found that the Media Information DS is able to represent these l:n relationships quite nicely. A more detailed description is presented in Section 3.

3.3 Creation Information The Creation Metalnformation DS (Figure 4) binds together creation and classification information about an AV content item as well as other material related to the AV content item. We acquire this information in a variety of ways, including: •

Automatic extraction from the header of an Internet stream.



Automatic extraction from the referring Web page that contains the link (URL) to the Internet stream.



XML delivery of metadata from Internet streaming media encoding firms and content producers. We can process any XML and transform it to the Streaming AV DS schema via XSL. [10]

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The CreationDescription is an instance of the Structured Annotation DS, which provides the so-called 6W descriptors (who, what event, what object, when, where, why). It allows us to group controlled vocabulary terms about the streams that are available directly from content producers or which can be automatically assigned via expert system rules or machine learning algorithms.

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We use the role element of the Creator DS to identify primary creation roles such as author and artist.

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Figure 4. CreationMetalnformation DS The creation information available from Internet streaming media is typically quite limited: •



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The screen shot of RealProducer TM (see Figure 5) illustrates the typical creation information available as part of the Intemet streaming media encoding processfl Typically, only the title, author, and copyright are completed.

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The controlledTerm descriptor allows us to organize and distinguish various controlled vocabularies. For example:

1D3vl meta tags [11], the defacto MP3 metadata standard, include title, artist, album, year, genre and a comment feld. ID3v2 meta tags have a much richer syntax, but are not widely encoded. [12]

J RealNetworks provides command line tools allowing the scripting/automation of creation information ("Clip Information") after encoding. See



W h o : Company name, Stock ticker symbol, Sports competitor, Sports team name



W h a t Event: Sports competitive class, event type (regularly scheduled, one-shot, etc.)



W h e n : Release date



W h e r e : Sports team location

The TextAnnotation element is used for any searchable free-text element such as an abstract, keywords, and album description.

http:llservice.real.comlhelp/library/guides/producer/htmfiles/co mmand.htm.

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3.4 Classification

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The Classification DS is used as part of the larger CreationMetalnformation DS, to categorize Internet streams into a proprietary taxonomy. This allows our customers to provide tabs or a directory-like browse feature for their search engine users.

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Our high level categories (Music, News, Sports, Radio, Television, Finance, and Other) are represented by the PackagedType element. Subcategories are represented by the Genre element, which has been enhanced to be hierarchical.

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We use the Related Material DS, also part of the CreationMetalnformation DS, to hold information about Web page(s) that contain links to streaming media. Most lnternet search engines have found that such data increases search precision and/or recall. [14] [15] Analogously this data has proved to be useful for automated classification [16].

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The Related Material DS nicely echoes the overall structure of the Streaming AV DS, containing a CreationMetalnformation DS, a Medialntbrmation DS, and a Usagelnformation DS. This makes tbr efficient XSL processing and database structures.

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4. MPEG-7 MDS DEFICIENCIES AND ENHANCEMENTS

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We encountered some challenges with representing media and content information with the ultimate goal of search. Here we discuss some of those challenges and propose several solutions.

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4.1 Media Information

For Web pages, we encode the Media Locator D with the referring page URL, the Title DS in the Creation DS with the referring page title, and the CreationDescription DS with the HTML anchor text and meta tags (e.g., description, keywords).

As tbllows we present some difficulties we found representing media information.

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Currently we do no actively segment any video or audio, i.e., the only segments are those distinct Intemet-accessible URLs, which are described in their entirety. Most streams only need a single high-level segment that represents the entire duration of the content. For audio-visual content, (e.g., a RealVideo stream of a newscast), it would be more sensible and efficient for us to have a single AudioVisualSegment DS containing the relevant subDS's. However, MPEG-7's "class" hierarchy requires that video information be placed under a VideoSegment, and audio information under an AudioSegment.

3.6 Usage Information We simply use the Rights DS within the UsageMetalnformation DS to capture the copyright.

3.7 Spoken Text Spoken text is extracted via speech recognition tools, closed caption decoding, or transcripts provided by the content producer. Spoken text is captured as a text string in our own simple Spoken Text DS as part of the AudioSegment DS. (See Figure 2.)

While the AudioSegment and VideoSegment DS's identify the media type, a more useful location for such identification would be an element in Medialnformation DS. Currently the Medialnformation DS (or Medialdentification DS within the Medialnformation DS) does not have a simple enumerated media type (e.g., {audio, video, text, animation 3D}). The Medialdentification DS's VisualDomain and AudioDomain are intended to "inform about the source, acquisition and/or use", rather than provide a definitive media type. Although such information could be inferred from some other MediaFormat elements (e.g., CompressionFormat), we find that less direct than we would like.

3.8 Summary Information The MPEG-7 SequentialSummary DS is used only when we need to represent multiple key frames extracted from a single Internet streaming video.

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We have enhanced the MediaFormat DS by adding:

5.1 eXcelon Prototype Implementation



FileCreationDate element is often distinct from the content creation date and may be different for each MediaProfile element.



Boolean "Live" element MediaFormat length and inconsequential.

to indicate that Segment duration

The eXcelon X M L server allowed us to simply "drag and drop" X M L files into a data store and use XQL queries against collections of these documents. 2 This system allowed very rapid development of an X M L database and full-text queries.

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After about 20,000 records, performance was not acceptable. No further investigation was performed to determine the cause of the performance degradation.

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We have enhanced the MediaCoding DS by adding: Scalable element. Currently this is a Boolean, which indicates that a single URL provides multi bit rate support. Some customers wish to feature these streams (e.g., Real's "Multi-rate SureStream, as shown in Figure 5). A more complete implementation would allow list or range of supported bit rates. We expect this to become more important as scalable MPEG-4 implementations become commercially available. •



5.2 XML Schema-driven RDBMS Implementation Using Java, we wrote a tool that generated Java classes and an Oracle RDBMS schema from an XML Schema. The resulting RDBMS schema was fully normalized, and contained over 50 tables and 50 classes, each with Get/Set methods lbr each property. Additionally, iterators were generated to for any l:n relationships.

Boolean Seekable element. This indicates whether the user can adjust the playback position. This is always false Ibr live streams, but is occasionally false for ondemand streams (e.g., advertisements).

One particular difficultly we had was representing arbitrary IDIDREF relations. IDs and IDREFs are not typed in XML. Relational queries cannot handle navigation through 1DREFs without a join for each referenced type. [ 19]

Audio Emphasis element. MP3 audio may be encoded with 4 different audio emphasis values. [ 17]



Encryption is a controlledTerm element.



DRMScheme is a controlledTerm anticipating a variety of commercially digital rights management schemes. As this directly affects the coding, and may be different for each MediaProfile, it belongs in the MediaCoding DS rather that the UsageMetalnformation DS.

The complexity of the MPEG-7 schema and the nabvet6 of our class and RDBMS schema generator resulted in an unwieldy implementation, and was quickly jettisoned before significant development occurred with the generated Java classes. We did not have the opportunity to implement the results of any recent research regarding efficient mapping of XML into an RDBMS schema. [20], [21]

Internet streaming media URLs typically point to a text metafile rather than the actual AV content item. The metafile contains a URL that points to a streaming media server file using a real-time streaming protocol (e.g., RTSP). The HTFP MIME type of the metafile is typically media format-dependent so that an Internet browser can launch the correct media player. Thus Internet streaming media typically has two URLs associated with each streaming instance: a metafile URL and a streaming media server URL. We represent the streaming media server URL using the Medialnstance DS's InstanceLocator. We have added the "LinkToStream" as a second linking element in the MediaInstance DS. It is also of type "InstanceLocator".

5.3 Data Model The Streaming AV DS guides the development manually designed RDBMS schemas.

5.4 Stream Delivery Network We have developed an automated system to receive and process Intemet streaming media metadata from a network of streaming media encoding firms and audio-visual content providers. The goal is to minimize the development time required to bring a new "content partner" on board. We encourage our content partners to provide us their data in an X M L format. If they have no in-house XML DTD or schema, we encourage them to use the StreamingAV DS, which we have publicly available as an X M L Schema and as an XML DTD.

The Medialnformation DS's do not do a good job at describing multimedia material inside a hierarchical transport such as an MPEG-2 transport stream. To solve this problem, we suggest that a Media Profile DS be enabled to contain a Media Profile. See [18] for details.

Many X M L developers prefer the DTD version of the StreamingAV DS. Conversion from X M L Schema is relatively straightforward except for the use of polymorphism by the Person (Individual, PersonGroup and Organization) and Segment (VideoSegment, AudioSegment, and TextSegment) DS's. This requires some extra work and documentation for in the DTD version.

4.2 Creation Information To reduce our database complexity, we use the CreationDescription DS ' W h o ' fields to encode data that might otherwise encoded in CreationMetaInformation and UsageMetalnformation Person and Place DS's, for example, distributor, producer, creation location, etc. Losing structure that does not improve search simplifies the implementation.

For each proprietary schema we encounter, we write an XSL stylesheet to transform the data conforming to the proprietary X M L schema into an MPEG-7 StreamingAV description. We

5. IMPLEMENTATIONS We have used MPEG-7 Multimedia Description Schemes in a variety ways at Singingfish.com.

2 eXcelon includes basic full-text indexing and full-text search extensions to XQL.

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have developed over a dozen such XSL stylesheets. Each takes approximately 2-3 hours to develop and fully test.

[ 12] Nilsson, M. "ID3 tag version 2.3.0", 3 February 1999, http://www.id3.org/id3v2.3.0.html.

6. C O N C L U S I O N S

[ 13] "RealProducer Plus Production Guide", Chapter 3, RealNetworks, Inc., March 2000, http://www.service.real.com/help/library/guides/producerpl us7/htmfiles/use.htm.

We have described how MPEG-7 Multimedia Description Schemes are used to model the metadata of Interact streaming media. We have briefly described how the MPEG-7 MDS is used in two internal experiments, processes, as well as how it is used to exchange metadata with commercial content partners. Several weaknesses and additions to existing description schemes were provided.

[ 14] Brin, S., and Page, L., "The Anatomy of a Large Scale Hypertextual Web Search Engine", Proceedings of the Seventh International World Wide Web Conference, 1998, http://www7.scu.edu.au/programme/fullpapers/1921/corn 19 21 .htm.

7. A C K N O W L E D G M E N T S My thanks to the MPEG-7 MDS group for having patience with my intermittent ability to contribute to the effort. Special thanks to Dulce Poneeleon, IBM Almaden Research Center for encouraging me to write this paper.

[15] Chakrabarti, S., Dom, B., Raghavan, P., and Rajagopalan, S., "Automatic Resource Compilation by Analyzing Hyperlink Structure and Associated Text", Proceedings of the Eighth International Worm Wide Web Conference, 1999, http ://www.ahnaden.ibnl.com/cs/people/pragh/www9 8/4 3 8. html.

8. R E F E R E N C E S [ l ] Stern, J., and Lettieri, R., "RTSP vs. HTTP Streaming", QuickTime Pro 4: Visual QuickStart Guide, Peachpit Press, p.249, (1999).

[16] Attardi, G., Gulli, A., and Sebastiani, F., "Theseus: Categorization by Context", WWW8 Poster Paper, http://www.di.unipi.it/-attardi/Paper/wwwS/www8.hm~.

[2] Liu, C., "Multimedia Over IP: RSVP, RTP, RTCP, RTSP", http ://www.in g.puc.cl/~jnavon/II C35 82/Present/3/mmip.ht

[ 17],"Information technology - Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbits/sec - Part : Audio", ISO/IEC 11172-3, 1993-0801.

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[3] "MPEG-7 Generic AV Description Schemes (V0.7)", ISO/IEC JTC1/SC29/WGI 1 N2966, October 1999, Melbourne.

[18] Rehm, E., "System vs. Component Format/Coding in the Media Profile DS", ISO/IEC JTC1/SC29/WG11 M5478, December 1999, Maui.

[4] eXcelon is an XML data server built on top of the ObjectStore OODBMS. See http://www.exceloncorp.com for more details.

[19] Shanmugasundaram, J., Gang, H., Tufte, K., Zhang, C., DeWitt, D., and Naughton, J., "Relational Databases for Querying XML Documents: Limitations and Opportunities". Proceedings of the 1 9 9 9 VLDB Conference, September 1999, http://www.cs.wisc.ed u/niagara/papcrs/jay99.pd f.

[5] "MPEG-7 Multimedia Description Schemes WD (Version 1.0) ", 1SO/IEC JTC1/SC29/WG11 N3113, December 1999, Maui. [6] Ibid. [7] World Wide Web Consortium, "Synchronized Multimedia Integration Language", http://www.w3.org/AudioVideo.

[20] Florescu, D., Kossmann, D., "Storing and Querying XML Data using an RDMBS", IEEE Data Engineering Bulletin 22(3), 1999.

[8] "SMIL Quick Reference", RealNetworks, Inc., December 1998, http://service.real .com/hclp/librarv/guides/prod uction/htmfil es/smilref.htm.

[21 ] Zhang, C., Luo, O., DeWitt, D., Naughton, J., and Tian, F., "On the Use of a Relational Database Management System for XML Information Retrieval", February 2000, http://www.cs.wisc.edu/niagara/papers/czhang00.pdf.

[9] "All About Windows Media Metafiles", Microsoft Corporation, April 13, 2000, http://msdn.microsoft.com/workshop/inaedia/windowsmedia /crcontent/asx.asp

[22] "MPEG-7 Software integration guidelines & Workplan for DS integration", ISO/IEC JTC1/SC29/WG11 M5692, March 2000, Noordwijkerhout. [23] OpenSWF.org, "A Concise Guide to the SWF File Format", http://www.openswf.org/toc l_4.html.

[ 10] World Wide Web Consortium, "XSL Transformations (XSLT) Version 1.0", W3C Recommendation 16 November 1999, http://www.w3.org/TR/xslt.

[24] See http://www.activesky.com.

[11] Nilsson, M. "ID3 made easy", July 2000, http:/lwww.id3.org/id3v 1.html. 9B