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JPEG Lossless Compression (ISO/IEC 14495)

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name ISO/IEC 14495-1:1994 and -2:2003. Information technology -- Lossless and near-lossless compression of continuous-tone still images: Baseline and Extensions (formal name); Improved lossless JPEG (common name)
Description

Compression encoding for continuous-tone images with both lossless and near-lossless modes. Its baseline algorithm consists of two independent and distinct stages called modeling and encoding, based on the LOCO-I algorithm, which relies on prediction, residual modeling and context-based coding of the residuals. Most of the low complexity of this technique comes from the assumption that prediction residuals follow a two-sided geometric distribution and from the use of Golomb-like codes that are very good for geometric distributions. JPEG-LS was intended to provide a low-complexity, high quality image compression standard that could offer greater efficiency than JPEG_orig_LL, and that would provide superior decorrelation of the prediction residuals that are central to this encoding method. Meanwhile, the extensions in part 2 of the standard introduce such elements as arithmetic coding. Besides lossless compression, JPEG-LS also provides a lossy mode ("near-lossless") where the maximum absolute error can be controlled by the encoder. The relevant specifications are ambiguous as to whether the file formats (JFIF and SPIFF) listed in this description's Relationships may be used to wrap JPEG-LS data; Comments welcome.

JPEG-LS has been assigned PRONOM PUID fmt/150; the PRONOM Web page (consulted January 26, 2012) states that JPEG-LS "has faster compression than JPEG 2000 and is considered better than the original lossless JPEG standard."

Production phase May be applied in initial-state picture creation; often used for middle- and final-state archiving or end-user delivery.
Relationship to other formats
    Subtype of JPEG, JPEG Image Encoding Family
    Used by JFIF_1_02, JFIF JPEG File Interchange Format, Version 1.02
    Used by JFIF File Interchange Format, Versions 1.00 and 1.01, not described at this Web site at this time
    Used by SPIFF, SPIFF Still Picture Interchange File Format

Local use Explanation of format description terms

LC experience or existing holdings See JPEG
LC preference See JPEG

Sustainability factors Explanation of format description terms

Disclosure Fully disclosed. Developed by the Joint Photographic Experts Group (JPEG), formally known as ISO/IEC JTC 1/SC 29/WG 10.
    Documentation ISO/IEC 14495-1:1999 and -2:2003, Information technology -- Lossless and near-lossless compression of continuous-tone still images: Baseline and Extensions. Same as ITU-T Rec. T.87:1998.
Adoption Not known to the compiler of this description; Comments welcome. The CharLS JPEG lossless library site reports, "The biggest drawback of the JPEG-LS format is that it has so far not been widely adopted. If your application writes files to be read by other applications, it is unlikely that JPEG-LS will be supported by them."
    Licensing and patents See JPEG.
Transparency Depends upon algorithms and tools to read; will require sophistication to build tools.
Self-documentation Not investigated for this format description.
External dependencies None.
Technical protection considerations None.

Quality and functionality factors Explanation of format description terms

Still Image
Normal rendering Should be good but not known to the compiler of this description; Comments welcome.
Clarity (high image resolution) Should be very good, but source data is limited to 8-bits-per-channel. The CharLS JPEG lossless library site reports, "When you need to choose between JPEG-2000 and JPEG-LS, you should consider JPEG 2000 if you want to use multi-resolution images (say for images exceeding 10000 x 10000 pixels)."
Color maintenance Not investigated for this format description.
Support for vector graphics, including graphic effects and typography No support for vector graphics.
Support for multispectral bands See JPEG.
Functionality beyond normal rendering Not investigated for this format description.

File type signifiers Explanation of format description terms

Tag Value Note
Filename extension See note.  ISO/IEC 14495-1 and PRONOM (see PUID: fmt/150) associate this encoding with the "jls" extension, which may be applied as the extension for image data wrapped in JFIF_1_02, SPIFF, and JPEG_EXIF; Comments welcome.
Internet Media Type Not applicable.  See JFIF_1_02, SPIFF, and JPEG_EXIF.
Magic numbers Hex: 0xFF 0xD8
Start of Image (SOI) marker; see JPEG
Indicator for profile, level, version, etc. Hex: 0xFFF7
Start of Frame (SOF) marker for improved lossless baseline; see also JPEG. Note that the Web documentation of the JHOVE JPEG module states "JPG7 (0xF7), also known as SOF55, [indicates] a JPEG-LS file."
Indicator for profile, level, version, etc. Hex: 0xFFF9
Start of Frame (SOF) marker for improved lossless extended; see also JPEG

Notes Explanation of format description terms

General In addition to the Useful references in this description, see also the references cited in JPEG.
History  

Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: 12/09/2013