One of many ways to do it:
This plugin will allow you to automate various tasks using "Macros". Macros consist of a list of conditions under which a list of actions will be performed. Examples and guides can be found in the wiki. Feel free to contribute! If you run...
obsproject.com
You'll have to fill in the transition that you want, and if you don't like 0.5 seconds, you can change that too, in both places shown here. Independent for each video.