ViewerJS is the best, if not the only one. Its source is on github https://github.com/kogmbh/ViewerJS
The only thing you say is that you need to convert from ppt (microsoft) to odt (open document). I think that in the latest versions of mspowerpoint it is possible to save in open format (odt).
If not, you can always use OpenOffice / LibreOffice Impress to create presentations in open odt format or to convert from ppt to odt.
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