In recent versions of Avidemux, most of the function buttons are missing compared to 2.6.6.
How do I preview the Output version?
(Menu views attached. I can't seem to display them inline here.)
right hand bottom corner of avidemux worksurface under A and B time indicators:
Quote[v] Play filtered
enable (preview) or disable (source video)
Avidemux 2.6.branch has been simplified unified (developers prerogative) some time ago.