Sustainability of Digital Formats
 Planning for Library of Congress Collections

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Identification and description

Full name	Information technology -- Generic coding of moving pictures and associated audio information (formal name)MPEG-2, Main Profile
Description	Permits the use of Intra-coded (I) frames, predicted (P) frames, and bidirectionally predicted (B) frames. Conformance points for this bitstream exist at the following levels: Low, Main, High-1440, and High. At the Main Level, the broadcast-stream picture size is 720x576 pixels (non-square pixels), with color sampling of 4:2:0 and a maximum data rate of 15 Mb/s.
Production phase	Generally a final-state (end-user delivery) format; may be used as a middle-state (broadcast production) format.
Relationship to other formats
Subtype of	MPEG-2,

Local use

LC experience or existing holdings	See MPEG-2
LC preference	For file-based compressed video, conform to or approximate MPEG-2_422 (4:2:2 Profile) at Main Level (aka MPEG-2 422@ML) or MPEG-2_MP (this document; Main Profile) at Main Level (aka MPEG-2 MP@ML). Uncompressed or losslessly compressed copies are preferred to compressed (for future development).

Sustainability factors

Disclosure	Open standard. See MPEG-2
Documentation	See MPEG-2
Adoption	MPEG-2_MP (Main Profile) is used by broadcasters and cablecasters, who may also use MPEG-2_422 (4:2:2 Profile). Vanderbilt University is using MPEG-2_MP (Main Profile) as the "target" for its digitization of news broadcasts.
Licensing and patents	See MPEG-2.
Transparency	See MPEG-2.
Self-documentation	See MPEG-2.
External dependencies	See MPEG-2.
Technical protection considerations	See MPEG-2.

Quality and functionality factors

Moving Image
Normal rendering	Good support.
Clarity (high image resolution)	See MPEG-2. At a given picture size, data rate, and encoding algorithm, MPEG-2_MP (Main Profile) will produce greater clarity than MPEG-2_SP (Simple Profile) but less than MPEG-2_422 (4:2:2 Profile).
Functionality beyond normal rendering	See MPEG-2.

File type signifiers

Tag	Value	Note
Filename extension	mpg, mpeg	There is no explicit MPEG-2 file format; MPEG-2 content "ready to be delivered" is exchanged in files with these extensions.
Internet Media Type		See MPEG-2
Magic numbers		See MPEG-2

Notes

General
History

Format specifications

• See Disclosure under Sustainability factors.

Useful references