Sustainability of Digital Formats: Planning for Library of Congress Collections

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MPEG-4, Visual Coding, Main Profile

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name ISO/IEC 14496-2:2004. Information technology -- Coding of audio-visual objects -- Part 2: Visual. Main Profile (formal name); MPEG-4, Visual Coding, Main Profile (common name)
Description

See also MP4_FF_2 and MPEG-4_V. The Main Profile was created to serve broadcast services, permitting the highest quality, and supporting arbitrarily shaped objects using grayscale coding.

The Main Profile permits the use of the following visual object types:

  • Simple: rectangular video, uses intra (I) and predicted (P) video object planes (VOPs, the MPEG-4 term for frames).
  • Core: arbitrarily shaped video, uses a tool superset of Simple, adds bidirectional (B) video object planes (VOPs), binary shape coding, and supports temporal scalability based on sending extra P-VOPs.
  • Main: arbitrarily shaped video, adds to Core the coding of grayscale shapes, sprites (object in memory with all pixel information, e.g., the background of scene), and interlaced coding.
  • Scalable Texture: arbitrarily shaped still image with wavelet compression and incremental download.

Three compression levels are permitted; the highest accepts up to 32 objects (Simple, Core, or Main) for a maximum total bit rate of 38 Mbps.

Production phase Generally a final-state (end-user delivery) format.
Relationship to other formats
    Subtype of MPEG-4_V, MPEG-4, Visual Coding (Part 2)
    Used by MP4_FF_2_V, MPEG-4 File Format, V.2, with Visual Coding (All Profiles)

Local use Explanation of format description terms

LC experience or existing holdings  
LC preference  

Sustainability factors Explanation of format description terms

Disclosure Open standard. See MP4_FF_2.
    Documentation See MP4_FF_2.
Adoption Actual adoption not known to the compilers of this document.
    Licensing and patents See MP4_FF_2.
Transparency See MP4_FF_2.
Self-documentation See MP4_FF_2.
External dependencies See MP4_FF_2.
Technical protection considerations See MP4_FF_2.

Quality and functionality factors Explanation of format description terms

Moving Image
Normal rendering Good support.
Clarity (high image resolution) See MPEG-4 and MPEG-4_V. Potential for greater clarity at a given picture size, data rate, and encoding algorithm, than some other MPEG-4 profiles, e.g., Simple, Simple Scalable, Advanced Simple, and Core Profiles.
Functionality beyond normal rendering See MPEG-4.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension mp4
 
Internet Media Type See related format. 

See MP4_FF_2

Magic numbers See related format. 

See MP4_FF_2

File type brand (ISO Base Media File Format) See note.  Indicated in file wrapper and relates to "brands" defined in ISO_BMFF. Wrapping MPEG-4_V bitstreams in MP4_FF_1 would occasion the use of mp41; in MP4_FF_2, use mp42. See Part 15 of the standard, pp. 2-9, 13.
Indicator for profile, level, version, etc. See note.  Indicators for Main Profile, levels 2, 3, and 4 are 00110010, 00110011, 00110100, respectively. From Annex G of ISO/IEC 14496-2:2004, Table G.1

Notes Explanation of format description terms

General  
History  

Format specifications Explanation of format description terms


Useful references

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Last Updated: 02/21/2017