Improve scene change detection using selection area

[markmillerdev]

The fewer issues I have to read, the more new features I will have time to implement, so I ask that you please try these things first

• [X] Check out all the menus and keyboard shortcuts. Maybe the feature already exists?
• [X] Try with the newest version from GitHub
• [X] Read the documentation and FAQ, Known issues, Troubleshooting to see if the feature already exists
• [X] See if someone already suggested this under Issues or Discussions

Description

The "Detect Scene Change" function uses the entire image frame to evaluate change between two frames. This can result in false scene change detections when the subject is moving. To improve accuracy, the tool should allow the user to drag a rectangle over an area of the image to use for scene detection. In this manner, the user could choose an area which is visual distinct in each scene (as in cuts between two people talking). In would have a secondary benefit in speeding up the scene detection process.

[markmillerdev]

To clarify, the user would draw one single rectangle which would be used to evaluate scene change detection for the entire length of the video clip.