The PBCore metadata standard, based on the Dublin Core

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What exists beyond the world of MARC: Metadata Standards Review 1 - PBCore and media
asset management
By
Tom Adamich
Metadata standards have become an important topic of discussion in libraries of all types
in recent years. As the number and complexity of resources to be accessed in libraries of all types
multiplies exponentially, so does the need to provide access to these materials (not only in the
virtual PC environment but in the mobile segment of the virtual world as well). Each format
developed (particularly those that are multimedia-based) have associated metadata-based
documentation requirements that accompany them.
It is these multimedia-based products that are becoming a large part of library collections.
In multimedia creation and broadcasting circles, the phrase “media assets management” has
become a buzzword to describe the overall management of these resources for use in the
Internet-based virtual library environment. According to Andries in “Media Data Centre – The
Path to Performance and Efficiency in the Media Workflow, media asset management involves a
variety of Internet and file-based media production and delivery protocols which include the
following:
IP network-based access and transport of the media;
� central disk-based media storage;
� server-based (non-linear) video editing or processing;
� software-based media management and media production systems.
Together with the appearance of some product formatting standards like MXF (Material
eXchange Format) and AAF (Altered Auditory Feedback), which provide a generic file container
for the media essence (and associated metadata), these changes have led to the file-based
paradigm of media essence (Andries, 2010, 1)
The next step is to take the media essence (which may be found in a number of forms, including
but not limited to high-resolution video - for broadcasting via satellite or online, low-resolution
proxy video and audio - for website-based streaming media or other Internet-based applications)
and house it in a media assets management system (which will enable the media essence to be
transcoded and archived as well) (Andries, 2010, 3).
In this installment of “Making and Managing Metadata” we’ll examine the first of several
metadata standards which have been developed over the last few years as a result of the need to
store and document motion media in ways that are markedly different from tradition library
materials. One of those metadata standards is the PBCore metadata standard.
What is PBCore, and how can it benefit libraries?
The PBCore metadata standard, based on the Dublin Core Metadata Standard (ISO 15836), is
used to describe media (video, audio, text, images, rich interactive learning objects). According
to Pinch in Tools for Collaboration: PBCore and More, PBCore was created by the Public
Broadcasting community in the United States in 2005 with 48 elements. (Pinch, 2011, 4)
Version 2.0 was released in February, 2011 and now contains 80 elements. PBCore enables both
Public Broadcasters and related communities to easily retrieve and share media assets among
colleagues, various software systems, institutions, community/ production partners, private
citizens, and educators. PBCore can also be used as a foundation for an archival or asset
management process at an individual PBS station or institution.
Another advantage in using PBCore, according to Pinch, is the ability to amortize the cost of
gathering metadata information from multiple sources in the media production process
(producers, directors, technicians, etc.) by using one common platform that all stakeholders use
to contribute, manage, and share metadata. Thus, each party can contribute/manage/share
metadata instantaneously at their participation point in the media process rather than having the
content interpreted following production (which is the traditional media cataloging method used
in the past – often identified as “end-of-product cataloging”).
Libraries may have the opportunity to examine traditional end-of-product cataloging workflow to
determine what advantages may be realized when metadata which accompanies media received
by the institution is extracted and sampled for quality control purposes to determine if automated
metadata generation processes are functioning properly. Again, awareness that a metadata
standard such as PBCore has been used (or its derivatives such as Dublin Core or the European
Broadcasting Union Core – EBUCore – a standard to be profiled in a future Making and
Managing Metadata column) would promote metadata generation efficiency across the metadata
creation process (as well as make metadata readily available for access and modification, if
needed).
Ultimately, the goal of the PBCore standard is to provide a pivotal identification point for the
achievement of the real power of digital technology to meet the mission of public broadcasting –
access to quality media for all U.S citizens. For libraries, providing access to quality media
being generated on behalf of the communities they serve
http://www.pbcore.org
Who created PBCore, and what does it look like?
As mentioned earlier, PBCore was created in 2005 by a metadata working group
consisting of 30 representatives of local and national television and radio organizations. The
group’s advisors included the University of Washington Information School, the Department of
Defense’s Academic CoLab, and the Rutgers University/The Association of Moving Image
Archivists. Other PBS stakeholders were also involved in many of the preliminary discussions
Additionally, executives from the PBS flagship station WGBH administered the project.
(Brooks, 2009)
The following is an example of PBCore metadata record creation rationale as it relates to media
being described:
PBS Tapes
Here is a generic example of how a single PBS program, identified as “ABCD 101,” might
be represented by multiple master and backup reels (MR1, MR2, etc.) in the PBS library
system. In our PBS Archives PBCore sample records, I have chosen to document the
“Version 1” and “Version 2”-level information only.
Add the expanded layer of the upcoming PBS containerization effort, and the underlying
media/file list for every program could increase exponentially. This may have serious
implications for future extensions to the PBCore element set.
Other applications which may exist include displaying PBCore using the XML Stylesheet
Language (XSLT) to produce web pages and combining PBCore+XSLT+CSS into an
HTML stylesheet
According to PBS Executive Glen Chatworthy:
It can be hard for laymen to visualize the concept of “metadata” and PBCore. I
realized early on that I needed to find a way to display our PBCore records as web
pages so that I could display the results in a meaningful way for casual viewers.
In the course of producing my automation system, I learned just enough about
XML Stylesheet Language Transformations (XSLT) and Cascading Style Sheets
(CSS) to produce XML files that would display as web pages in contemporary
browsers. Sample runs include appropriate links in the PBCore XML files as well as
XSLT and CSS stylesheets in related directories.” (Chatworthy, 2009)
Below is an example of PBCore metadata standard output in a traditional library
catalog environment:
Home Page
http://www.mnvideovault.org/index.php
PBCore as a media asset metadata standard for libraries
Ultimately, the goal of PBCore will continue to be to provide documentation standards
and protocols for the Public Broadcasting community. However, the structure of PBCore itself
(and its Dublin Core origins) has the potential to enable the standard to be easily adapted and
utilized by libraries and other organizations faced with managing multimedia resources in an
Internet-based media assets management environment.
PBCore also has the potential to encourage libraries to examine their traditional end-ofproduct cataloging processes (with respect to media productions as well as other materials) to
determine if the metadata ingest and workflow processes associated with Public Broadcasting
media asset metadata creation and management (using PBCore or a similar metadata standard)
have the potential of being utilized/modified by the library community to promote efficiency,
save dollars, provide quick access to quality media resources, and act as an element of efficient
and effective media asset archiving and governance.
References:
Andries, Luc. 2010. Media Data Centre – the path to performance and efficiency in the media
workflow. In “EBU Technical Review”, 2010 Q4, 2.
Brooks, Marcia. 2009. Electronic mail correspondence, July 30, 2009; Accessed May 21, 2011.
Chatworthy, Glen. 2009. Electronic mail correspondence, July 15, 2009; Accessed May 21,
2011.
Jacobs, Bruce. 2009. Electronic mail correspondence, July 30, 2009; Accessed May 21, 2011.
Pinch, Peter. Tools for Collaboration: PBCore and More. Presented at the 2011 Integrated Media
Association Conference (Austin, TX : March 10-15, 2011). Available at:
http://pbcore.org/news/pbcore-presentation-at-ima-2011/ . Accessed May 31, 2011.
Additional Resource: Motion Media Glossary
Source of terms (used with permission)
Dan Rayburn
StreamingMedia.com
http://www.streamingmedia.com/glossary
Animation
A series of still images displayed quickly to simulate motion. Some key examples of Web
animation include Shockwave, Flash, and animated GIFs.
ASF
Most streaming media files encoded for use on the Windows Media platform have a .asf
extension. This is an actual audio/video file, as opposed to an ASX file.
ASX
A metafile which points to a Windows Media audio/video presentation.
AVI
(Audio/ Video Interleaved) - A Microsoft-specified format for saving audio and/or video clips,
referred to by Windows as "Video for Windows." You can play the files through the Media
Player in Windows or through many popular browser plug-in multimedia players.
Bit rate
The speed at which data travels from one place to another on a computer network, such as the
Internet.
Capture
Process of digitizing audio and video content from an analog format.
Digital Video
Digital video is the key to content when streaming media. Digital video is an alternative way of
storing or distributing video. Digital video is usually converted from an analog video source. A
digital video signal is represented in '1's and '0's, whereas an analog video signal is represented
by a fluctuating voltage signal that is stored on magnetic tape. This difference is similar to the
difference between analog audio and digital audio.
Digitizing
Process of capturing or "bringing in" audio and/or video (usually analog source tapes such as
Beta SP, 3/4, VHS, etc.) into a computer. Digitizing is made possible by video hardware, a
computer hardware card, cables, and a software application that all work together to convert the
original signal into digital media. This digital media can then be edited and transferred back to
numerous formats for Internet streaming, CD-Rom, DVD, and other forms of distribution.
Submitted by: Brian Tane
Frame Rate
The number of frames of video displayed during a given time -- usually measured in seconds.
Standard television video is almost 30 Frames Per Second (fps).
Flash
Vector-based animation format released by Macromedia often used for narrative productions on
the web.
Interframe method
Interframe method is a type of video compression used by MPEG which compresses three types
of frames: I-Frames, P-Frames and B-Frames.In I-Frames, the entire scene is compressed. PFrames are compressed with reference to a Past-I or P-Frame. B-Frames provide the highest
amount of compression but require both a past and a future frame as a reference. The image
sequence in MPEG is flexible, depending on application specific parameters.
Interstitial
Any web-based advertisement which occurs before, after, or during a narrative content
presentation. For example, if streaming media terminology were applied to regular television,
standard television commercials would be called interstitials, since they interrupt programming
ISDN
(Integrated Services Digital Network). A set of standards for transmitting digital information
over ordinary telephone copper phone lines and other media. With an ISDN adapter (both at your
computer and at your Internet service provider), you can send and receive transmissions much
faster than using a conventional modem.
M3U
A metafile which points to an MP3 stream.
MP3
MP3 is the MPEG audio layer 3 standard. Layer 3 is one of three coding schemes (layer 1, layer
2 and layer 3) for the compression of audio signals defined by the MPEG committee. Layer 3
uses perceptual audio coding and psychoacoustic compression to remove the redundant parts of a
sound signal. It also adds a MDCT (Modified Discrete Cosine Transform) that implements a
filter bank, increasing the frequency resolution 18 times higher than that of MPEG audio layer 2.
MPEG
MPEG is a digital video and audio compression format that was defined by the Moving Pictures
Experts Groups which is part of the International Standards Organization (ISO). MPEG is a lossy
compression method which uses Interframe compression. Interframe compression assumes that
although action is happening, the background in most video frames remains the same. This
means that it is not necessary to compress each entire frame, but only the differences between
them. The Interframe method compresses three types of frames: I-Frames, P-Frames and BFrames
MPEG-4
MPEG-4 defines how multimedia streams – video, audio, text, data – are transmitted as
individual objects. MPEG-4 is a compression/decompression technology that aims to achieve
interactivity, efficiency and stability in narrow-band transmissions. On a broader level, MPEG-4
aims to pave the way toward a uniform, high quality encoding and decoding standard, that would
replace the many proprietary streaming technologies in use on the Internet today. MPEG-4 is
also designed for low bit-rate communications devices, such as mobile receivers or wristwatches
that can display video. These devices are usually wireless and can have different access speeds
depending on the type of connection and traffic. To overcome this problem, MPEG-4 supports
scalable content. Content is encoded once and automatically played back and transmitted at
different rates, depending on the available network connection.
Multicast
A process which allows a server to send one stream to multiple recipients. This is different from
traditional streaming media, where each user connects separately to a server.
Narrowcast
To send data to a specific list of recipients. On the Internet, narrowcasting has also come to refer
to programming developed for "niche" interest groups.
Packet
A chunk of data organized in a block for transmission over an IP network. Usually contains
header information with origin and source address, and employs error-correction.
Pointer files
Text files that point to the actual location (server and filename) of a streaming file. Almost all
systems use pointer files.
Progressive Download
A method of delivering audio/video data over the Internet that involves playing the downloaded
portion of a file while the download is still in progress. Also referred to as "Pseudo-Streaming".
protocol
A uniform set of rules that enable computers to connect to one another. Protocols determine how
data is transmitted between computing devices and over networks. As such they define issues
such as error control and data compression methods.
QuickTime
Multimedia architecture used by software tool vendors and content creators to store, edit and
play synchronized graphics, sound, video, and music.
RAM
A metafile which points to a RealMedia file.
RealMedia
Brand name describing file formats, server software, player software, and protocols used by
streaming media systems from RealNetworks, a leading streaming media platform vendor.
RealAudio©, RealVideo©, and RealFlash© are examples.
Rich Media
Media that has been enhanced with animation or video. Rich media ads are animated, and often
streamed, so that they appear more like television commercials, as opposed to ads containing
static images and text. They can be embedded in Web pages and inserted into or between video
clips. Using SMIL, they can be streamed concurrent to audio programming.
RTP
(Real Time Protocol) – An Internet protocol that defines the transmission of real-time data, such
as audio and video. RTP provides mechanisms for the sending (server) and receiving (client)
applications to support streaming data.
RTSP
Real-Time Streaming Protocol: a standard method of transferring audio and video and other
time-based media over Internet-technology based networks. A descendent of UDP.
Simulated live
Describes a completed audio/video program which is presented on the web as though it were
live. Audience members must tune in to the program. If the scheduled start time has already
passed, audience members will join the program in progress (also referred to as video on
demand – VOD).
SMIL
Synchronized Multimedia Integration Language. A text-based mark-up language used to
synchronize disparate media elements (such as text, animations, audio and video) within one
streaming media presentation.
streaming media
Streaming media technology enables the real time or on demand distribution of audio, video and
multimedia on the internet. Streaming media is the simultaneous transfer of digital media (video,
voice and data) so that it is received as a continuous real-time stream. Streamed data is
transmitted by a server application and received and displayed in real-time by client applications.
These applications can start displaying video or playing back audio as soon as enough data has
been received and stored in the receiving station’s buffer. A streamed file is simultaneously
downloaded and viewed, but leaves behind no physical file on the viewer's machine.
UDP
User Datagram Protocol. A method of communicating between computers which does not
guarantee that ever bit arrives at its end destination. Favored for time-sensitive data such as
streaming media.
Unicast
A process which forces each individual user to make an individual connection to a server to
receive a stream (as opposed to Multicast, which allows multiple, simultaneous access to a
stream).
Video Compression
The process through which a complete video file is reduced in size. Video Compression
algorithms take advantage of the fact that there is minimal difference from "one" frame to the
next. The first frame is encoded and then the sequence of differences between frames. This is
also known as "inter-frame" coding or "3D coding"
Video On Demand
Describes video content which may be viewed by the end-user from beginning to end, at any
time.
WAV
(Wave Form Audio) - Files with the .wav extension are digital representations of sound and
typically take up a good deal of space to store (typically 50MB for a 5 minute song, for instance).
If you use software to rip files from an audio CD, it is usually stored in .wav format. Standard
Windows sounds are also stored in .wav format.
Webcasting
A live broadcast format over the World Wide Web (WWW).
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