Created attachment 181396 [details] Sample slide (PPTX) with video Here we have a slide with a video playing (in an infinite loop) in the background and some elements in the forefront. Impress does not show these elements while the video plays nor after, though it does show them in edit mode. Version: 7.5.0.0.alpha0+ / LibreOffice Community Build ID: 41f02927b6d8470c298c8a2f407c98420a5ebe24 CPU threads: 8; OS: Linux 5.18; UI render: default; VCL: gtk3 Locale: en-US (en_US.UTF-8); UI: en-US Calc: threaded (Similarly for 6.4 - 7.3 I tested.)
Created attachment 181397 [details] Screenshot with PowerPoint in presentation mode
Confirmed using LO 7.5.0.0.alpha0+ (28daee8a3252e03a67484dc8d3dd26fd73af4826) / Ubuntu. In earlier versions, eg. 4.x the video doesn't even play, probably due to some codec or multimedia lib issue. We can probably assume this was never okay.
Created attachment 181501 [details] Alternate, more complex, sample document (PPTX) I wonder whether / believe that this, somewhat more complex, sample document with two slides including a background video is about the same issue - if possibly from a slightly different angle.