Sustainability of Digital Formats: Planning for Library of Congress Collections
Sustainability of Digital Formats: Planning for Library of Congress Collections |
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| Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact | |
| Full name | ISO/IEC 11172. Information technology -- Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s (formal name), MPEG-1 (common name) |
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| Description | Compression encoding for video that may be accompanied by audio, identical to ITU-T (International Telecommunications Union-Telecommunication Standardization Sector) recommendation H.261. Low bandwidth, originally developed to store video on media like CDs; later widely used in online environments. |
| Production phase | Generally a final-state (end-user delivery) format. |
| Relationship to other formats | |
| Has subtype | MP3_ENC, MP3 audio encoding |
| Used by | QTV_MPEG, QuickTime MPEG |
| Has subtype | MPEG_layer_2_audio, MPEG-1 and MPEG-2 Layer II Audio Encoding |
| LC experience or existing holdings | Used extensively for access copies of American Memory reformatted moving image content, ca. 1990-2010. |
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| LC preference | For preservation reformatting, the Library of Congress' Packard Campus for Audio-Visual Conservation has chosen MPEG-2, Main Profile (lossless JPEG 2000 wrapped in MXF operational pattern 1a). |
| Disclosure | Open standard. Developed through ISO technical program JTC 1/SC 29 for coding of audio, picture, multimedia and hypermedia information by Working Group 11 (WG11) aka the Moving Picture Experts Group (MPEG). |
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| Documentation | ISO/IEC 11172; first approvals in 1991. Five parts have been published; parts 1, 2, and 3 are central. See list of ISO documents in Format specifications below. |
| Adoption |
Widely adopted for filemaking and World Wide Web access. Many software tools exist for encoding and decoding. |
| Licensing and patents | None known |
| Transparency | Depends upon algorithms and tools to read; will require sophistication to build tools. |
| Self-documentation |
Technical (coding) information is contained in the MPEG-1 bitstream in various headers. Image height and width, for example, are embedded within the sequence header. The lack of metadata of the type called descriptive by librarians motivated the MPEG group to develop MPEG-7, a separately standardized structure for metadata to support discovery and other purposes. |
| External dependencies | None |
| Technical protection considerations | None |
| Moving Image | |
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| Normal rendering | Good support. |
| Clarity (high image resolution) | Moderate. Typical files have a picture size of 352x240 pixels (non-square pixels) and a data rate of 1.5 Mb/s, which means that only field of each video frame is captured. One commentator (http://www.faqs.org/faqs/mpeg-faq/part1/) reports that the source input format (SIF) for MPEG-1 "is CCIR-601 [component video] decimated by 2:1 in the horizontal direction, 2:1 in the time direction, and an additional 2:1 in the chrominance vertical direction. And some lines are cut off to make sure things divide by 8 or 16 where needed." Outcome will depend on the type and extent of compression, and the encoder used. |
| Functionality beyond normal rendering | None |
| Sound | |
| Normal rendering | Good support. |
| Fidelity (high audio resolution) | Moderate, given that this is a format for compression. Audio layer three encoding in the standard is also known as MP3_ENC. Outcome will depend on the type and extent of compression, and the encoder used. |
| Multiple channels | MP3 supports five main channels and an optional LFE (Low Frequency Encoding or Effects) channel, i.e., 5.1 surround sound. |
| Functionality beyond normal rendering | None. |
| Tag | Value | Note |
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| Filename extension | mpg mpeg |
There is no explicit MPEG-1 file format; MPEG-1 content "ready to be delivered" is exchanged in a de facto file format that may carry one of these extensions. |
| Internet Media Type | video/mpeg |
From IETF (Internet Engineering Task Force) RFC 2046 |
| Internet Media Type | video/mpv video/mp1s |
From IETF (Internet Engineering Task Force) RFC 3555; these subtypes are glossed as "MPEG-1 or -2 Elementary Streams" and "MPEG-1 Systems Streams." |
| Internet Media Type | video/mpg video/x-mpg application/x-pn-mpg video/x-mpeg |
Additional examples selected from The File Extension Source. |
| Magic numbers | Hex: 00 00 01 Bx ASCII: .... |
From Gary Kessler's File Signatures Table. |
| Pronom PUID | fmt/649 |
See http://www.nationalarchives.gov.uk/PRONOM/fmt/649 for MPEG-1 Elementary Stream. |
| Pronom PUID | x-fmt/385 |
See http://www.nationalarchives.gov.uk/PRONOM/x-fmt/385 for MPEG-1 Program Stream. |
| Wikidata Title ID | Q336284 |
See https://www.wikidata.org/wiki/Q336284. |
| General | |
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| History | MPEG stands for the Moving Picture Experts Group, which began developing video compression standards in the 1980s. The group was founded by two men described by one commentator as "the fiery Leonardo Chiariglione (CSELT, Italy)" and "the peaceful Hiroshi Yasuda (JVC, Japan)." MPEG's initial development was partly inspired by the H.261 video coding standard published by the ITU (International Telecom Union). |
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