How to minimise size of .ppt presentations without losing Pictures and Audio in LibreOffice/WPS-office?

I am trying to decrease the size of my .ppt presentations by converting them to .odp/.wps-format, since they take several GBs memory because of - big pictures and - audio content in slides. I would like to store the presentations in smaller space without losing quality i.e. picuters and audio. WPS Office --- WPS office > Save as > jpg of every slide; which does a very good work in extracting the images; I have not found yet any terminal tool for the task of many .ppt files; the 2-month-old release is alpha but much more stable than the previous ones (> 100 Mb .ppt files) and can render much better .ppt files than LibreOffice presentation. I already contacted the company about the task with a link to this thread. I already sent a related question in their Linux Community of the application but they have not approved it yet here . LibreOffice --- I do when I have soffice in my PATH but get masi@masi:~/$ ppt2odp test.ppt > Failed to connect to /usr/lib/libreoffice/program/soffice.bin (pid=10643) in 6 seconds. > Connector : couldn't connect to socket (Success) > Error: Unable to connect or start own listener. Aborting. > masi@masi:~/$ OS: Debian 8.5 64 bit Linux kernel: 4.6 Hardware: Asus Zenbook UX303UA