ITU-T Recommendation T.851:

ITU-T T.81 (JPEG-1)-based still-image coding
using an alternative arithmetic coder

Reference software implementation


In an effort to accelerate the adoption of ITU-T Recommendation T.851, ASIC North, with the encouragement of IBM, in conjunction with the Independent JPEG Group, has generated example software of the alternative arithmetic coder. IBM proposes that the provided patch, in conjunction with IJG's version 6b, be adopted as an appendix to Recommendation T.851 to serve as reference software. This appendix can be revised when an improved update version is available.

The current provided version is an early "alpha" version and supports baseline, sequential, and progressive modes. "Alpha" version means that basic functionality is provided but robustness and stability is known to be lacking, and failures occur in some conditions. Subsequent versions will address these issues.


Download Source Code

Version 6b of the IJG code:

Version 1c of the T.851 patch code:


Installation Instructions

Untar/unzip the IJG 6b package: 

    tar xzf jpegsrc.v6b.tar.gz
This will create a folder "jpeg-6b" in the current location.
Copy the AN_T.851_v1c.patch.gz file into this folder: 
    cp AN_T.851_v1c.patch.gz jpeg-6b
Change into the "jpeg-6b" folder and unzip the AN_T.851_v1c.patch.gz file: 
    cd jpeg-6b
    gunzip AN_T.851_v1c.patch.gz
Patch the IJG version 6b code with version 1c of the T.851 code: 
    patch < AN_T.851_v1c.patch
Configure and build the software: Follow the instructions in install.doc.

Note: Only the automatic "configure" script was updated for the T.851 code. If you wish to configure the software by hand, use the makefile.cfg as a template for modifying the Makefile for your platform.


Copyright and no-warranty notice for the software patch contained within AN_T.851_v1c.patch

In no event shall ASIC North, Inc. be liable for any damages whatsoever (including, without limitation, damages for loss of profits, business interruption, loss of information, or any other pecuniary loss) arising out of or related to the use or inability to use this software. ASIC North, Inc. disclaims all warranties, express or implied, including but not limited to, warranties of MERCHANTABILITY and FITNESS FOR A PARTICULAR PURPOSE.
This software is provided "AS IS", and you, its user, assume the entire risk as to its quality and accuracy.

This software patch is

copyright (C) 2005-2006, ASIC North, Inc. &
copyright (C) 2006, Independent JPEG Group.
ASIC North, Inc. hereby grants permission to use, copy, modify, and distribute this software (or portions thereof) for any purpose, without fee, subject to the conditions given in the IJG README file.


Intellectual Property Rights notice of ITU-T Rec. T.851 (09/2005)

ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.

As of the date of approval of this Recommendation, ITU has received a notice from IBM of intellectual property, protected by patents, which may be required to implement this Recommendation. These patents are royalty-free for this Recommendation. No other patents have been brought to the attention of the ITU. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.


Compression comparison results

Compression comparison results with various entropy encoders and settings are listed in the following document:


Feedback & Support contact

Further development of the software will be maintained by the Independent JPEG Group.
For requests, comments, and questions regarding this software implementation please contact guido at jpegclub period org.

Page last modified 6 Jun 2006 by Guido Vollbeding.