Jpylyzer 2 release candidate

31 October 2019

We are happy to present you the release candidate for Jpylyzer 2.0.0. The final, stable release is foreseen for the last week of November. Unlike previous releases, jpylyzer 2.0.0 will be a major release that introduces some breaking changes with respect to previous versions. Below is a short overview of the main changes. Scroll to the bottom of this post for links to downloads and revised documentation.

Validation of raw codestreams

Jpylyzer is now capable of validating ‘raw’ JPEG 2000 codestreams. Codestream validation can be activated by setting the new --format switch to value j2c. When jpylyzer is used as a Python module, use the checkOneFile function’s new validationFormat argument and set it to j2c (e.g. myResult = jpylyzer.checkOneFile(myFile, 'j2c')). Although raw codestreams are pretty rare in the wild, having the ability to validate codestreams can be useful for validating individual JPEG 2000 encoded frames that are wrapped inside video containers. Note that the parsing of any video container formats is the responsibility of the user, as this is not supported by jpylyzer.

MIX output

It is now possible to report additional output in NISO MIX format using the new --mix option. The MIX functionality was developed by Thomas Ledoux of Bibliothèque nationale de France.

Support for additional codestream marker segments

This release adds support for the following (optional) codestream marker segments:

  • COC (Code style component)

  • QCC (Quantization component)

  • POC (Progression order change)

  • RGN (Region of interest)

  • CRG (Component registration)

These marker segments are now fully parsed and validated, and their associated properties are included in the output (previous versions would simply report the presence of these markers as empty elements).

Changes to the output format

The addition of the codestream validation option made it necessary to make some changes to jpylyzer’s output format that break compatibility with previous versions. Since there was no way to avoid some breaking changes anyway, we decided to take this as an opportunity to address some further inconsistencies in jpylyzer’s output format. The changes are:

  1. The isValidJP2 element is superseded by the new isValid element. This element has a format attribute which defines the validation format, which is either jp2 or j2c (in the case of a codestream).

  2. The top-level output element is now always <jpylyzer> (confusingly, previous versions would add a <results> element if either the --wrapper or --recurse options were activated). This top-level element contains one <toolInfo> element, and one or more <file> elements. Each <file> element then contains the usual <fileInfo>, <statusInfo>, <isValid>, <tests> and <properties> elements. The --wrapper option has been deprecated (since the output of each analysed file is now wrapped by default).

  3. The reported values of the precincts property have been changed to “default” (previously: “no”) and “user defined” (previously: “yes”). The old values falsely suggested that precincts were altogether absent in “default” case.

  4. Precinct size (precinctSizeX, precinctSizeX) values are now also reported for the “default” case (see above).

  5. If the --mix option is used, MIX output is written to a new propertiesExtension element inside the properties element.

For more details, have a look at the jpylyzer 2.0 XSD schema.

Backward compatibility

Since the new output format will break existing workflows that expect jpylyzer 1.x output, we added a --legacyout option that results in output that follows the old 1.x format. Note that codestream validation and the reporting of MIX output are disabled if this option is used!

Continuous integration improvements

In addition to the above changes, which are all directly visible to the user of the software, a lot of development effort has been dedicated to automating various components of the jpylyzer release process. This includes static code analysis and the addition of automated tests. In particular:

  • In order to better assess the quality of pull requests, code is now automatically checked for compliance against PEP 8 and PEP 257. Code is also analysed with Pylint. In addition to this, the existing code base has been been cleaned up in places to improve the compliance to these standards.

  • A basic framework was set up for running unit tests. This makes it possible to create automated tests using files from the jpylyzer-test-files corpus (the addition of any actual tests will follow in the near future).

Packaging

The packaging workflows for both the Windows binaries and the Debian packages have been given an overhaul.

Package downloads

Debian packages and Windows binaries for this release candidate are available from the link below:

https://software.openpreservation.org/releases/jpylyzer

Installation with pip

If you want to install this release candidate with pip, make sure to run pip with the --pre option (by default pip ignores pre-leases, and the --pre switch overrides this behaviour).

Documentation

Full documentation can be found here:

Feedback

Any feedback on this jpylyzer release candidate is greatly appreciated. Also, don’t hesitate to contact us if any of the (new) packages for some reason do not behave as expected (preferrably using the issue tracker).

Happy jpylyzing!