catppt doesn't output contents of LibreOffice documents saved in .ppt format

[skierpage]

catppt does output the text of the really basic Windows PowerPoint file /media/Windows/Windows/System32/MSDRM/MsoIrmProtector.ppt , but it doesn't output anything from files saved by LibreOffice Impress in "PowerPoint 97-2003 (.ppt)" format.

The Linux file utility reports

test_LO_file.ppt: Composite Document File V2 Document,
 Little Endian,
 Os: Windows,
 Version 1.0,
 Code page: -535,
 Title: ...

That code page -535 looks bad, but file tests/test_LO_file.doc reports the same and works.

[skierpage]

Seems WPS office files also fail, at least the baloo_test_WPS.ppt file attached to KDE bug 438455 outputs only "Office Theme", "1_Office Theme", .. "12_Office Theme", and not the text on the slide.