This is a topic that was raised before about 2 years ago (https://patchmypc.com/forum/index.php?topic=2811.msg7391#msg7391) but as far as I can tell it has not been resolved. The subject line pretty much says it all. Avidemux keeps reinstalling and will not install silently. Dialogue boxes come up and the installation will not proceed without options being selected.
Sorry about this but Avidemux no longer has a silent switch so we will have to removed it soon from Patch My PC.