DATE: December 18, 2001
REVISED:
NAME: Coding Electronic Formats for Different Media in Field 007 of the MARC 21 Bibliographic and Holdings Formats
SOURCE: MARC Advisory Committee
SUMMARY: This paper discusses coding electronic formats in field 007 of the MARC 21 bibliographic and holdings formats.
KEYWORDS: Computer Files (BD, HD); Field 007 (BD, HD); Sound Recordings (BD, HD); Videorecordings (BD, HD)
RELATED: 98-6 (January 1998); 2001-08 (June 2001)
STATUS/COMMENTS:
12/18/01 - Made available to the MARC 21 community for discussion.
01/21/02 - Results of the MARC Advisory Committee discussion - Some participants agreed that field 007 is too complex to accurately code and promote effective information retrieval. Other participants, however, stated that field 007 prevents coding ambiguity through its consistent and controlled vocabulary. There was consensus that controlled vocabulary is useful, although not necessarily in coded form. Because of the rapid changes in technology and vocabularies, it may be more practical to use words rather than codes for this type of information. Consensus favored broadening code s (Electronic) in field 008/23 (Form of item) for Books, Music, Serials, and Mixed Materials and position 008/29 for Maps and Visual Materials.
Discussion Paper 2002-DP01: Coding Electronic Formats for Different Media in Field 007
1.1 Coding Electronic Formats in MARC 21
Electronic resources are coded in several different places in MARC 21. Leader/06
(Type of record) is used to indicate the type of record and the 008 field (Fixed-length
data elements) is used for information about the content of the material. If
in electronic form, the item is coded for its content rather than its physical
carrier. Field 006 (Fixed-length data elements - Additional material characteristics)
may be added for additional characteristics that should be recorded and field
007 (Physical description fixed field) may be added for coded information about
its physical format.
Proposal 2001-08
(Coding DVDs in Field 007 for Videorecordings in the MARC 21 Bibliographic and
Holdings Formats) suggested adding a new code to the Videorecording 007/04 field
to identify a DVD. During the discussion, many participants questioned whether
field 007 would effectively accommodate the current and future proliferation
of new electronic formats. Because many of the new formats contain both sound
and video data (i.e., DVD-As and enhanced CDs both contain music videos), MARC
users may have difficulty discerning the primary content models for these items.
Adding codes for new formats that emerge, however, may not be possible because
certain character positions have almost reached their size capacity. For example,
the Videorecording 007/04 (Videorecording format) character position currently
contains 18 codes representing different videorecording formats. Because of
these factors, it is important for the MARC community to assess the need for
using defined codes for physical format information.
Over the last few years, there has been a huge increase in the availability of different electronic formats for visual, audio and storage data. Because libraries collect and maintain items in many of these new formats, it may be important to code for them in MARC 21. See the Appendix for a list of the most popular formats.
2.1 Coding Future Electronic formats in the MARC Formats
2.1.1 Sound Media
Field 007 for sound recordings contains special coded information about the
physical characteristics of a sound recording. Fields 007/01 (Specific material
designation) and 007/13 (Capture and storage technique) are two positions that
differentiate digital formats from other media. For example, 007/01 specifies
that a DVD-A is a sound disc (code "d") and 007/13 (code "d")
indicates that it provides digital storage.
Potentially useful descriptions of digital formats are sampling and bit rates.
Bit rate provides an approximate bandwidth figure at which a stream may
be played over the Internet and is thus an indication of how fast a connection
must be to stream a file without interruptions. Bit rate is usually measured
in kilobits per second (Kbps). Sampling rate measures the precision with
which a digital file describes the analog sound it represents. It is the number
of times per second that the original sound source was sampled during recording
and is measured in kilohertz (KHz). To further identify and differentiate new
digital sound media, two new character positions could be defined for bit rate
and sampling rate in field 007.
Because audio files also contain different bit depths (or sample sizes), it
may be advantageous to define a character position for bit depth in the Sound
recordings 007 field. The character position could resemble the Computer file
007/06-08 field (Image bit depth) that uses either a three-character number
or alphabetic code to indicate the bit depth of an image. Alternatively, the
Computer file 007/06-08 field could be expanded to include bit depth measurements
for both image and audio files.
A new character position could also be added in field 007 for "Sound recording
format" that resembles Videorecording field 007/04 (Videorecording format).
It could contain codes for each type of media, such as a code for DVD-A, a code
for CD, and code for Minidisc, etc. Although this character position may be
helpful in differentiating between audio formats, it is restricted to only 25
codes (including a fill character ( | )). With the huge proliferation of new
audio media, 25 codes may not be enough to accurately describe them.
Because a lot of the new audio media allow for multichannel playback, which
includes surround sound playback, a code may be added in field 007/04 (Configuration
of playback channels) for it. Alternatively, code "q" (Quadraphonic)
could be redefined as "Quadraphonic, multichannel, or surround" which
is consistent with the definition in Videorecording 007/08 (Configuration of
playback channels).
Because MP3 refers to a compression format and not to a specific audio sound
format (although many MP3 files contain audio), it may not be useful to code
the Sound recording 007 field when cataloging them. A Computer file 007 field
could be used, but there is currently no element in it to code for compression
scheme or file format type. In the expansion of this field, compression scheme
was considered too changeable and not useful information. It is possible, however,
to add a Computer file 007 field to indicate the device needed for the MP3 file
to assist in resource management activities. For example, some MP3 files are
downloaded onto optical discs (007/01 code "o") or may be accessed
remotely (007/01 code "r"). One may provide additional information
about the specific file format or peripheral equipment needed (such as a MP3
player) in note fields, such as 500 (General note) or 538 (System details note).
2.1.2 Video Media
Field 007 for videorecordings contains special coded information about the
physical characteristics of a videorecording. Unlike the Sound recordings 007
field, it provides format-specific information. Position 007/04 (Videorecording
format), for example, is a one-character code that indicates the recording format
for videotapes or videodiscs. In June 2001, code "v" (DVD) was defined
in 007/04 to include the DVD-V medium. Additional codes for Video CD (this could
also include Super VideoCDs), Digital cassettes (this could also include DV,
DVC and D1 - D9 formats), Digital Betacam 8, CD-i, CDV, D-VHS and VCD formats
could also be defined in field 007/04. Defining these codes would leave no codes
remaining (codes "#" and "n" are obsolete) for future media,
however. To prevent depleting the codes, one could use code "z" (Other)
in field 007/04 to indicate new electronic formats and record their specific
names in note fields.
During the discussion of Proposal
2001-08 (Coding DVDs in Field 007 for Videorecordings in the MARC 21 Bibliographic
and Holdings Formats), it was suggested that field 007/07 (Dimensions) be expanded
to include diameter values to enable users to code for optical discs (the field
currently is defined only for width measurements). Although there are standard
sizes of optical discs, the sizes remain somewhat fluid and thus, coding for
diameter in 007/07 may not provide useful descriptive information. For example,
smaller 3 inch diameter DVD discs may be produced commercially instead of the
usual 4 3/4 inch diameter discs.
2.1.3 Data Storage
Electronic formats for data storage may be coded based on the contents of
the data stored. For example, audio files stored on a DVD-ROM would be coded
as sound recordings. The 008 for Computer files may be used if a storage medium
contains the following classes of material: computer software (including programs,
games, fonts), numeric data, computer-oriented multimedia, and online systems
or services.
To provide further description for data storage media, the definition of code
"o" (Optical disc) in Computer file 007/01 may also be expanded to
include DVD-ROM, DVD-RAM, DVD-R, DVD-RW and DVD+RW. Because re-writability is
important to note in data storage formats, adding another character position
for it may also be useful for description and resource management activities.
Codes could include values for "Read-only," "Write once"
and "Write multiple times."
2.2 Code "s" (Electronic) in Field 008
Proposal 98-6 (Definition of Value "s" (Electronic) in 008 Character Positions) proposed adding a code in the 008 field to indicate that the carrier of an item is electronic. Although coding field 007 is mandatory when the physical form of a resource is a computer file, the MARC Advisory Committee felt that the 008 field should be used to ensure that electronic materials are properly identified. As a result, value "s" (Electronic) was added to 008/23 (Form of item) for Books, Music, Serials, and Mixed Materials and a new character position 008/29 was defined for Maps and Visual Materials (with the same codes as in 008/23). The definition of code "s" is:
Code "s" indicates that the item is intended for manipulation by a computer.
The item may reside in a carrier accessed either directly or remotely, in some
cases requiring the use of peripheral devices attached to the computer
(e.g., a CD-ROM player). This code is not used for items that do not
require the use of a computer (e.g., music compact discs, videodiscs).
With new electronic formats, the distinction between those that require the use of a computer and those that do not is not always clear since many formats may be played either on a computer or on media-specific devices. For example, most new computers contain DVD players that play CDs, CD-ROMs, and many different types of DVDs (DVD-A, DVD-V, DVD-ROM, DVD-RAM, etc.) One may also play these media on specific devices, such as DVD-players for video and DVD players found on modern audio stereo units. Moreover, MP3 files may be accessed remotely from the Internet (thus, requiring a computer) or may have previously been downloaded onto a compact disc or another medium. In the current rules, remotely-accessed MP3 music files would be coded "s" (Electronic) in the Music 008/23 (Form of item) field, but would be coded fill ( | ) if it had been previously downloaded onto a compact disc. Because of this ambiguity, consideration may be taken to update the definition of code "s" to include all electronic media.
2.3 Expanding the Computer File 007 Field
It should be considered whether some of the digital aspects of these formats could be added in an expanded Computer file 007 field with or without adding a Sound recording or Videorecording 007 field in the record. The 007 for computer files currently includes fourteen different character positions, many of which may be useful in differentiating between digital sound and video recordings. For example, it includes character positions for both "Level of compression" (007/12) and "Image bit depth" (007/06-08). Character positions for re-writability, bit rate, sampling rate, and playback type could also be defined to accommodate several other electronic resource characteristics. When the field was expanded for reformatted computer files, however, it was decided that the use of the shortened Computer file 007 (/00-/06) indicated a non-reformatted file. How to expand the field, but allow for coding a shorter one is questionable.
2.4 Usefulness of Coded Fields
There has recently been discussion on the MARC electronic discussion list about the usefulness of the MARC 21 fixed fields for data description and resource discovery. Several people expressed concern that fixed fields, such as fields 006, 007 and 008, are either not supported or used by some library systems or libraries do not consistently code them. Many responded that they preferred using note fields instead of coding fixed fields. Because of limitations to the fixed-length fields, and the constant flux in digital formats, the MARC community should consider their usefulness. Coding format names (such as DVD) in note fields in a consistent way would ensure accurate information retrieval and allow for more in-depth descriptions. Field 538 (System details note), for example, has been used to record the type of digital medium and other physical details for electronic formats. Moreover, the physical description data for electronic formats may also be placed in field 300 (Physical description).
DVD-R (DVD-Recordable) is a write-once medium that is similar to the CD-R medium. It records data sequentially and is compatible with other DVD drives and players. There are two types of DVD-Rs: DVD-R General and DVD-R Authoring. DVD-R stores about 4.7 gigabytes of data and is used primarily for archiving.
DVD-RAM (DVD-Re-writable) is an erasable, re-recordable version of DVD-ROM. It is suited for use in computers because of its hardware-based defect management features. DVD-RAM may hold 4.7 gigabytes of data and provide random access to recorded data. It may be rewritten more than 100,000 times and records at 22.16 Mbps.
DVD-ROM is the base format from which the re-writable DVDs originate. It is a popular read-only digital medium for data storage. It resembles the CD-ROM and is found on many desktop, notebook and ultra portable computers. DVD-ROM is backwards compatible with CD-ROMs, CD-Is, and video CDs and because of its popularity, many CD-ROM drive manufacturers plan to cease their CD-ROM products in favor of the DVD-ROM. A DVD-ROM may hold 4.7 to 17 gigabytes of data and have access rates of between 600 Kbps to 1.3 Mbps.
DVD-RW (DVD Re-recordable) is a re-writable version of the DVD-R. It is a phase-change erasable format that is playable in most DVD players and intended to be used in authoring and consumer video and audio recording. It records data sequentially and holds about 4.7 gigabytes of data per disc. DVD-RW discs can be rewritten about 1,000 times.
DVD+RW is a competing format with both DVD-RAM and DVD-RW and is incompatible with them. It is supported by Sony, Philips and Hewlett-Packard, however, the DVD-Forum (the membership organization that defines DVD standards) does not support it. DVD+RW can be rewritten one thousand times.
Electronic Formats for Sound Media
DVD-A (DVD-Audio) is a logical DVD format. It provides in stereo and multi-channel surround sound in a wider range of specifications than other digital sound media. It may also contain a limited amount of video and may be played in Video-Capable Audio Players (VCAPs). DVD-A supports a significantly higher quality of PCM (Pulse Code Modulation) audio than is possible with CDs and DVD-Vs and also includes copyright protection and watermark features.
Minidisc was developed by Sony as a replacement for cassette tapes. It is a digital audio playback and recording system that use 64 mm erasable magneto-optical discs. The Minidisc is a cross between a CD and an audio cassette with a sound quality equal to CDs. The Minidisc uses ATRAC audio compression. It stores about 74 to 80 minutes of sound and is re-writable. The Minidisc is no longer sold to consumers.
MP3 is a compression format for audio files developed by the Moving Picture Experts Group (MPEG). MP3 files resemble WAV files, but are much smaller. Because of their size, MP3 files have been used prevalently for creating, downloading, storing and playing audio files from the World Wide Web. Many electronic book companies also offer books in the MP3 format. Playing MP3 files requires either a Pentium or PowerPC processor, or an MP3 player. MP3 players are usually portable, however, future stereo systems may also include them.
SACD (Super Audio CD) was created as a competitor to the DVD-A format. Unlike CDs and DVDs that use PCM (Pulse Code Modulation) technology, SACD uses Direct Stream Digital (DSD) recording technology and accommodates more than four times more audio data than CDs. It may also store text and images and copyright protection information.
Electronic Formats for Video Media
CD-i was developed as a specialized, interactive application of CD for custom players that connect to televisions. It also includes a digital video feature based on MPEG-1 compression.
CDV (Video Single or CD-Video) is a hybrid between CDs and laserdiscs. CDVs contain 20 minutes of digital audio that is playable on CD players, DVD players or CD-compatible laserdisc players. It also contains 5 to 6 minutes of analog video and digital audio in laserdisc format that is playable only on CDV-compatible systems.
Digital Betacam provides professional video quality that is backwards compatible with analog Betacam versions. It uses a digital VTR (Video Tape Recording) recording format and mild data compression. Digital Betacam also has single frame insert editing capabilities.
DVC/DV (Digital Video Cassette or Digital Video) includes the DVCAM and DVC PRO formats. It is made up of 1/4 inch metal evaporated tape and records high quality digital video. It is considered a "prosumer" product because it is used by consumers, video enthusiasts, and professionals. DVC/DV uses the same sample rate as D-1, D-5 or Digital Betacam formats and is compressed with Discrete Cosine Transform (DCT) encoding specifications.
DVD-V is a logical DVD format that has been used since 1996. It is based on a plastic, reflective disc, usually 4.7 inches in diameter, that provides more than two hours of high-quality digital video. DVD-V uses a digital technique called PCM (Pulse Code Modulation) to represent video information. Interactive features, such as menus, can also be included on it. DVD-V is usually known as simply "DVD" and usually holds video-recorded movies.
D-VHS (Digital (or Data) VHS) is oriented more to the consumer market than other digital video formats and is backward-compatible with VHS. It does not, however, convert or record digital data, but only records and reads bit streams.
VCD (Video CD) stores visual or sound data that are controlled using different playback screens. It uses the same CD technology as audio CDs and CD-ROMs, however, it is optimized for the playback of audio and video media. The VCD uses MPEG-1 compression and also provides cross-platform compatibility with PCs, Macs, dedicated VideoCD players, and CD-i systems. The SVCD (Super Video CD) stems from the VCD technology and is used predominately in Asian countries. Its quality is consistently between that of VCDs and DVDs. The SVCD uses MPEG-2 encoding specifications.
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