How can less than a full screen appear?

When this code, on an html page, is viewed, via mobile device, you can tap the screen and the mobile device recording full screen successfully appears:

<input type="file" name="Upload" id="fileToUpload" accept="video/*" capture="user" onchange="submitForm();">
<input type="submit" value="Upload" name="submit" id="go" style="display: none;"/>

how/what can I add so that the less than the full screen appears?

I know it’s disheartening when you get no reply. I have had a Google around, as you probably have and can’t find any answer.
I wonder if it can be done in Javascript?


@ChrisjChrisj What I understood from your query is, that you want to say you don’t want to be record the full screen ? am I getting it correctly ?