Sample of an evening presentation without visuals, but with significant Q&A session.

Visual aids (powerpoint for example when available) are edited into the video.  With long presentations, some cruel editing of the material might be required, or perhaps on-screen help as to where we are in the sequence; or graphic overlays to aid clarity of the subject.

Here (in French), an evening of presentation 
is divided into
overview, details and responses to questions - by question.  
Above is the overview section of 15 minutes, 
the full program is available on the YouTube channel playlist - 
all sections are public.