New DjVu Version 25 Has Compatibility Issues
a news report by PlanetDjVu, July 15, 2003

Important Update - July 16:

We have just learned that DjVu Solo, DjVu Editor, DjVu ActiveX Control for MS Office, and the Any2DjVu conversion server all contain a "magic number" of "25", which causes them to refuse to decode a DjVu file with Version 25 or above.  This was originally compiled into these applications by AT&T Labs, long ago. It is possible that LizardTech was not even aware of this "magic number" feature.  It was not anticipated when the software was written that DjVu Version numbers would increment so quickly. It was only anticipated that version numbers would increase when the format upgrade was not backwards compatible. The Version 24 and Version 25 updates to the file format numbering this year were, in fact, probably not necesssary.

I would seem that an easy fix to this problem would be an update to the DjVu 4.1 plugin that saves DjVu pages as Version 24 (or even Version 23), and not Version 25.

This is an "honest problem", and not any attempt by LizardTech to make the DjVu format more proprietary.

- PlanetDjVu

If you save a DjVu file using the new Version 4.1 DjVu Browser Plug-in, and you use the "Save Page As" option, it is saved as a Version 25 DjVu. If you use the "Save Document As" option, the DjVu file is saved with the existing Version number intact.

Note that when the DjVu file is a single-page document, the "Save Document As" option is disabled and only the "Save Page As" option is available. When the DjVu file is a multi-page document, both the "Save Document As" and "Save Page As" options are available. Again, only the "Save Page As" option creates a Version 25 DjVu file in this 4.1 plug-in update.

As you may recall, LizardTech introduced Version 24 in March, to add support for the Leadtools Annotations library.

This format upgrade is completely undocumented - it is not even mentioned in the Readme file of the installation.  Version 24 was also undocumented, but at least we understood why it was done (the introduction of annotations).

The first compatibility problem with Version 25 DjVu files is that it is only the Windows plugin, and no other DjVu applications, that are currently writing Version 25 files. As a result, all other DjVu viewers will now display an upgrade message, such as this one from the DjVu Browser Plugin Versions 3.6 and 4.0:

Slowview Compatibility Issue

In Slowview 1.0, there is a controlled error message when a non-AT&T DjVu file is displayed:

Now, when a new Version 25 file is opened, the application crashes with the following error:

DjVu Solo Compatibility Issue

In DjVu Solo 3.1, the following upgrade message appears (which also has appeared when editing DjVu Versions above Version 21).

Now, with a Version 25 DjVu file, and unlike previous versions, a new message appears:

Then, the DjVu document is blanked out (not decoded for display).

DjVu Editor Compatibility Issue

Similarly in DjVu Editor (the earlier version that shipped with DjVu Workgroup), when you open a Version 25 file you get the following message,( which also has appeared when editing DjVu Versions above Version 21):

Now, with a Version 25 DjVu file, and unlike previous versions, a new message appears:

DjVu ActiveX Control for Microsoft Office Compatibility Issue

When you try to embed a DjVu file in a Microsoft Office document, and the version of the DjVu file is Version 25, you get the following error message, and the DjVu file is not decoded:

There is no problem embedding DjVu versions prior to Version 25.

Any2DjVu Conversion Server Compatibility Issue

We tried to OCR this Version 25 DjVu file with the Any2DjVu Conversion server. It produced the following error message:

Now running OCR on the document...
Processing page 1 file://localhost/home/djvuzone/ FAILED DjVu Decoder: Cannot decode DjVu files with version >= 25 *** Decoding failed on page 0 *** (djvurtk.cpp:562) *** int main (int, char **)

Unix and Mac

We did not test Version 25 files using the DjVuLibre compiled binaries. We have a report that Verison 25 files display (decode) OK in the DjVuLibre browser plugin for Unix (with the usual upgrade message).

We have also not tested the Mac plugins.


You can get around this problem by opening the Version 25 DjVu file in the DjVu Browser Plugin 4.0, then use "Save Page As". This will save it as a Version 24 file. Or open it in DjVu Browser Plugin 3.6.2, then use "Save Page As". This will save it as a Version 23 file. Version 24 and Verison 23 DjVu files can be edited in Solo, Editor and Any2DjVu with no problems.

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