How can I make obs set the canvas size to the size of a selected region in a window

[Donner]

How can I make obs record a selected region of a window and set the canvas size appropriately?

I want to record an area of e.g. a LibreOffice Writer window as I type. The dimension of the output video is to reflect the dimension of the area I selected exactly - no transformation should be applied.

How do I specify the region of interest. I figured out that I can change the size of the frame in the obs preview pane by holding the alt key while dragging the frame border/line. (The color of the frame changes from red to green.) Is that the correct way to do so?

Most importantly: How can I make obs change the size of the canvas to that selected area, as I don't want black areas around the region of interest. I want to record a window (part of it) because that window does not always have the focus or is in the background and I do not want to show what's in the foreground. So screen recording is what I want to avoid strongly.


&tldr;
My screen size is 1920x1080, the window size is smaller, the region I want to record is still smaller and the output video shall have that exact size.
In the screenshot below only the clear area shall be recorded. How can I achieve that?

Thank you :)

 

[bruce.]

I have the same question. This has been addressed also on 7 July 2021, 8 Dec 2020, 7 Oct 2019, 28 Nov 2018, and 13 Jan 2018 at least. It appears that this occurs when one's CANVAS resolution is bigger than the Windows Capture. I set the Base and Output resolutions to low values, but this has not changed the output, to my knowledge. I use the current version of OBS.
What would you suggest?