unoconv PPT failed transfter to PDF but Blank pages

[hacker-looper]

I was use unoconv to transfer PPT files to PDF, it's good for many, but few was failed with blank, I was confused because it was successfully running without any error log, see below:

root@iZ23cy8d37aZ:/mnt# sudo unoconv -vvv -f pdf -p 2000 1.ppt
Verbosity set to level 3
Using office base path: /usr/lib/libreoffice
Using office binary path: /usr/lib/libreoffice/program
DEBUG: Connection type: socket,host=127.0.0.1,port=2000;urp;StarOffice.ComponentContext
DEBUG: Existing listener not found.
DEBUG: Launching our own listener using /usr/lib/libreoffice/program/soffice.bin.
LibreOffice listener successfully started. (pid=6917)
Input file: 1.ppt
Selected output format: Portable Document Format [.pdf]
Selected office filter: [impress_pdf_Export]
Used doctype: presentation
Output file: 1.pdf
DEBUG: Terminating LibreOffice instance.
DEBUG: Waiting for LibreOffice instance to exit.

Original PPT:
1.ppt

Generated PDF:
1.pdf

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I've found an interesting thing is after saving this ppt file to pptx, it as successful transferred.
And I have to support both ppt and pptx.
Please Help !

[regebro]

Sorry that nobody was maintaining this and didn't answer your question. The files are no longer accessible, so I can't test this.