Sustainability of Digital Formats: Planning for Library of Congress Collections

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High-Throughput JPEG 2000 File Format

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name JPEG HTJ2K File Format [From ISO/IEC 15444-15:2019 Information technology — JPEG 2000 image coding system — Part 15: High-Throughput JPEG 2000]

The High-Throughput JPEG 2000 container format (with the JPH file extension) is specified by the ISO/IEC 15444-15:2019 Information technology — JPEG 2000 image coding system — Part 15: High-Throughput JPEG 2000 and identical ITU–T Rec T.814 standards. JPH files contain the HTJ2K or High-Throughput JPEG 2000 encoding, described in HTJ2K with support for modern color spaces, supporting High Dynamic Range (HDR) with better precision, and allows for the representation of raw color. The JPH file format updates JPEG 2000 formats, including JP2_FF and JPX-FF.

Comments welcome.

Production phase May be applied in initial-state picture creation, but often used most often for middle- and final-state archiving or end-user delivery. Comments welcome.
Relationship to other formats
    Subtype of ISO_BMFF, ISO Base Media File Format
    Contains HTJ2K, JPEG 2000 Part 15, High Throughput (HTJ2K)
    Modification of J2K_C, JPEG 2000 Part 1, Core Coding System
    Affinity to JP2_FF, JPEG 2000 Part 1 (Core) jp2 File Format
    Affinity to JPX_FF, JPEG 2000 Part 2 (Extensions) jpf (jpx) File Format

Local use Explanation of format description terms

LC experience or existing holdings The Library of Congress does not have any JPH files inventoried in its collections.
LC preference Neither JPH or the associated HTJ2K encoding are listed in the Library of Congress Recommended Formats Statement (RFS). See the RFS for the Library of Congress format preferences for Still Image or Moving Image in its collections.

Sustainability factors Explanation of format description terms


Fully disclosed. This is an ISO published standard, specified in ISO/IEC 15444-15: Information technology — JPEG 2000 image coding system — Part 15: High-Throughput JPEG 2000 and co-published as ITU-T T.814.


ISO/IEC 15444-15: Information technology — JPEG 2000 image coding system — Part 15: High-Throughput JPEG 2000

Also co-published as ITU-T T.814 : Information technology - JPEG 2000 image coding system: High-throughput JPEG 2000.


Per the HTJ2K whitepaper, there are several proposed usage scenarios for HTJ2K including management of cinema content, high resolution image capture, and web server image delivery. Consult the white paper beginning on page 8 for a more detailed description of the usage scenarios including tracing each usage scenario through the encoding architecture.

Distribution, archival and management of cinema and video assets. JPEG 2000 is a widely used distribution format for video content that can be transcoded into a variety of other streaming video formats. The Society for Motion Picture Television Engineers (SMPTE) has already defined this specification for the Interoperable Master Format for content delivery but this workflow can now be improved by HTJ2K. SMPTE has added HTJ2K to MXF (link). Per the white paper, "this should make it easy to adapt HTJ2K to D-Cinema, IMF and other MXF-based applications."

Energy efficient image capture and preview. Encoding to HTJ2K requires very low energy in software, GPU, or hardware. The HTJ2K encoding and JPH file format are highly desirable as image capture formats for mobile phones, digital camera, and more advanced devices. Because of the resolution scalability feature of HTJ2K, the JPH file can be interactively previewed with extremely low energy, unlike JPEGs.

Live performance, view finding, and telepresence systems. Because of HTJ2K’s high encoding and decoding throughput and low latency, high quality 4K content can be streamed over conventional IP and wireless links.

High resolution video capture. As stated in the white paper, "most mobile devices do not have sufficient CPU power to compress high resolution video streams." HTJ2K circumvents this problem by allowing compressed streams to be produced in real time. HTJ2K encoded video can be decoded with very high throughput with modest demand on hardware resources."

Cache management for interactive rendering. HTJ2K provides a more energy efficient way to handle applications of JPEG 2000 that renders content multiple times, especially large images that viewed interactively. Per the JPEG white paper, "If the original media uses the J2K code blocker, code-blocks that are being repeatedly accessed can be transcoded to an equivalent HT representation and stored within an intelligent content ache, where re-rendering becomes much less expensive."

Optimized image delivery in webservers. HTJ2K provides a great opportunity to address the goals of the "responsive images initiative" which refers to the need to adapt image resolution to better match the device display. Resolution scalability and cropping combinations can all be served from one JPH file, which reduces the web server’s workload. An example of HTJ2K decoding in a web browser can be found here.

Comments welcome.

    Licensing and patents

See HTJ2K.


See HTJ2K.


See JP2_FF.

External dependencies None.
Technical protection considerations

See JP2_FF.

Quality and functionality factors Explanation of format description terms

Still Image
Normal rendering Good support.
Clarity (high image resolution) See JPH_FF for characteristics of the image encoding.
Color maintenance

Per the JPEG HTJ2K primer white paper, "The HTJ2K standard defines a wrapping file format known as JPH, which extends the JP2 file format with support for modern parameterizable color spaces, images without any color space, and custom color mappings suitable for raw sensor compression."

As documented in Annex D of the ITU-T T.814 specification for High-Throughput JPEG 2000, the JPH file formats support additional color specification method (METH) values. The ISO/IEC 15444-1 JPEG 2000 encoding defines a method for embedding profiles in JP2 files, which is further expanded upon in ITU T.814.

  • Values 0-2 refer to METH values specified in ISO/IEC 15444-1 and ITU-T T.8000
  • Value 3 refers to the color Specification box indicates that the codestream can be embedded with any input ICC profile, contrary to the restricted ICC method defined for J2K_C.
  • Value 5 refers to the parametrized colorspace specified in Rec. ITU-T H.273 and ISO/IEC 23001-8.

JPH file formats only support a single alpha channel, unlike JP2 file formats. However, JPH files support multiple channels associated with the same color.

Additional information on the color specification box can be found on page 54 of Annex D of the T.814 specification.

Comments welcome.

Support for vector graphics, including graphic effects and typography

See HTJ2K.

Support for multispectral bands

See HTJ2K.

Functionality beyond normal rendering

See HTJ2K.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension jph
Defined via Annex D of the Rec. ITU-T T.814 specification.
Internet Media Type image/jph

See IANA registration

Internet Media Type image/jphc
Refers to content that consists of a single HTJ2K codestream. See ITU T.814 Annex E.
Wikidata Title ID See note.  No Wikidata Title ID for the JPEG HTJ2K High Throughput encoding at this time.
Pronom PUID See note.  There is no PRONOM PUID for the JPEG HTJ2K High Throughput at this time.

Notes Explanation of format description terms


See HTJ2K.


See HTJ2K.

Format specifications Explanation of format description terms

Useful references


Last Updated: 11/23/2022