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|HTJ2K Encoding [From ISO/IEC 15444-15:2019 Information technology — JPEG 2000 image coding system — Part 15: High-Throughput JPEG 2000]
The High-Throughput JPEG 2000 (HTJ2K) encoding provides a modification to the JPEG 2000 Part 1 encoding by introducing a new HT block coder, which serves as a drop-in replacement for the original JPEG 2000 block coder, known as J2K_C and is standardized in ISO/IEC 15444-15:2019.
Per HTJ2K's "High Throughput JPEG 2000 (HTJ2K): Algorithm, Performance and Potential" white paper, this new encoding provides an order of magnitude increase in throughput to JPEG 2000, "approximately 10x for moderate to high compressed bit rates and more than 30x for lossless coding." Because HTJ2K serves as a drop in replacement for the J2K-1 algorithm, the HT block coder can be used with all technologies described in the JPEG 2000 family of standards. In that case, HTJ2K preserves all features of JPEG 2000 Part 1 encoding besides quality scalability but includes support for resolution scalability, multi-spectral and hyper-spectral content, and non-iterative rate control among others. See J2K_C and JP2_FF for a review of the features associated with JPEG 2000 Part 1. HTJ2K also provides for reversible transcoding to and from J2K-1.
Because of HTJ2K’s efficiency and high throughput, it supports needs of professional video capture, mobile and satellite imaging applications, efficiency image capture, preview, and browsing. See JPH_FF for more details on the usage scenarios for HTJ2K and the JPH file format.
See Notes for more information about the encoding and testing.
|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
|J2K_C, JPEG 2000 Part 1, Core Coding System
|JPH_FF, JPH (HTJ2K) File Format
|MXF, Material Exchange Format (MXF)
|MXF_GC_UNC, MXF Generic Container Mapped to Uncompressed Images
|LC experience or existing holdings
|The Library of Congress does not have any JPH files inventoried in its collections.
|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.
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.
As of June 2019, the International Telecommunications Union’s (ITU) prepared the above-mentioned ISO standard as the ITU-T T.814 standard. This standard is specified in the ITU-T T. 814 Information technology – JPEG 2000 image coding system: High-throughput JPEG 2000.
As stated in the ISO/IEC 15444-15 standard, "Recommendation ITU-T T.814 (2019) is a common text with ISO/IEC 15444-15:2019, both in their first edition."
As of October 10, 2022 this ISO standard is in published status. Per the defined scope language in ISO/IE 15444:15, "specifies an alternate block-coding algorithm that can be used in place of the block-coding algorithm specified in ISO/IEC 15444-1. This alternate block-coding algorithm offers a significant increase in throughput at the expense of slightly reduced coding efficiency, while a) allowing mathematically lossless transcoding to and from codestreams that use the block-coding algorithm in ISO/IEC 15444-1, and b) preserving codestream syntax and features specified in the JPEG 2000 Part 1 Codec."
The Kakadu SDK supports HTJ2K and the JPH_FF file format in conjunction with supported features from the following JPEG 2000 standards; Part 1, Part 2, Part 3, and Part 9. See Notes for links to related ISO specifications.
There are also a variety of open source implementations of HTJ2K including but limited to:
|Licensing and patents
Per HTJ2K's "High Throughput JPEG 2000 (HTJ2K): Algorithm, Performance and Potential" white paper, the HTJ2K encoding on the JPEG 2000 is a royalty free standard. Kakadu LTD, as owner of the intellectual property behind the technologies of the HT block coding algorithm and the FBCOT framework, has made royalty free declarations to the ITU and ISO. Kakadu’s objective is to maintain the royalty free status for the entirety of JPEG 2000 standards.
Depends upon algorithms and tools to read; will require sophistication to build tools.
|Technical protection considerations
|Clarity (high image resolution)
|Excellent support. See J2K_C.
|Support for vector graphics, including graphic effects and typography
|No support for vector graphics.
|Support for multispectral bands
|Functionality beyond normal rendering
|Includes features for error resiliency. Also see J2K_C.
|This description is for the HTJ2K codestream encoding. See related file format JPH_FFfor filename extension.
|Internet Media Type
|See related format.
|Wikidata Title ID
|No Wikidata Title ID for the JPEG HTJ2K encoding at this time.
|There is no PRONOM PUID for the JPEG HTJ2K encoding at this time.
Joint publication of HTJ2K specifications by ITU and ISO/IEC. The JPEG High-Throughput encoding is published as ISO/IEC 15444 Part 15 and as ITU T.814. Per the defined scope language in ISO/IE 15444:15, "this alternate block-coding algorithm offers a significant increase in throughput at the expense of slightly reduced coding efficiency, while a) allowing mathematically lossless transcoding to and from codestreams that use the block-coding algorithm specified in Rec. ITU-T T.800 | ISO/IEC 15444-1, and b) preserving codestream syntax and features specified in Rec. ITU-T T.800 | ISO/IEC 15444-1."
ITU published an equivalent technical report as T.814 Information technology – JPEG 2000 image coding system: High-throughput JPEG 2000. The summary of T.814 includes, "Rec. ITU-T T.814 | ISO/IEC 15444-15 specifies a high-throughput (HT) block-coding algorithm that can be used in place of the block-coding algorithm specified in Rec. ITU-T T.800 | ISO/IEC 15444-1. The HT block-coding algorithm increases decoding and encoding throughput and allows mathematically lossless transcoding to and from the block-coding algorithm specified in Rec. ITU-T T.800 | ISO/IEC 15444-1. This is achieved at the expense of some loss in coding efficiency and substantial elimination of quality scalability."
Additional related specifications:
Regarding HTJ2K.com. The HTJ2K site provides a high level overview of the encoding and related file format while also consolidating resources for interested researchers and users. The site is owned and maintained by Kakadu Software Pty, who own the property rights over the HT block coding algorithm that is the key component of the new encoding.
Regarding encoding. As stated in the "High Throughput JPEG 2000 (HTJ2K): Algorithm, Performance and Potential" white paper, the HT block coding algorithm is faster than traditional J2K-1 implementations. The J2K-1 algorithm is based upon the Embedded Block Coding with Optimized Truncation (EBCOT) algorithm used in conjunction with the Discrete Wavelength Transform (DWT). The HTJ2K encoder uses the Fast Block Coding with Optimized Truncation (FBCOT) algorithm to achieve targeted compression size but also works in conjunction with DWT to produce sub-bands and LL sub-band. The HT algorithm, like J2K-1, adopts a coding pass structure (see page 12 and 13 of the white paper), with Cleanup, SigProp, and MagRef coding passes. Based on the end to end encoding and decoding system, the new HTJ2K code-stream can be almost 10 times faster than the J2K-1 algorithm with much larger speedups, "on the order of 30x for lossless compression and decompression." (see page 4 of the white paper). The new HT block coding algorithm can be used with many of technologies described in the JPEG 2000 standards family while retaining most existing features, while also supporting completely lossless transcoding to and from code-streams that have been generated using the original J2K-1 algorithm.
For a diagram of the overall architecture, see Figure 2 on page 4 of the JPEG primer white paper or Figure 2 on page 12 of the May 2020 High Throughput JPEG 2000 white paper. The HTJ2K compression and decompression system preserves the existing architecture and syntax of JPEG 2000. The white papers describe in more detail the components of the HTJ2K architecture and the process of input images to the decompressed images.
Regarding testing. The following summarizes JPEG’s 2022 published case study on High-Throughput JPEG 2000’s performance on laptops and desktops. A 2018 15-inch MacBook Pro with 16GB RAM and Intel i9 processor was used for speed testing with four primary software applications.
As indicated in Figure 1 and Figure 2 from the JPEG 2022 case study, HTJ2K performed comparably to Apple ProRes, which surpassing ProRes in distortion efficiency. This summary won’t dive into the mathematical specifics of the rate-distortion performance, but further details can be found in the case study on page 4.
The following list summarizes the development work of the ISO/IEC 15444-15 standard from the initial Call for Proposal (CfP) in 2017 to its submission to ISO in early 2019. This list summarizes the ISO/IEC JPEG meetings that occur four times a year to discuss and develop related standards.