OBS Tip: Use bounding boxes for your capture sources
When watching Twitch streams, I occasionally see streamers manually moving, aligning and scaling (or even stretching) their videogame capture sources repeatedly, every time they capture something different. There is an OBS feature called Bounding Box that can take care of that for you.
In your stream layout you might have a nice space prepared for the game source, or even if you don’t, you probably want it properly maximized instead of at the resolution and position it has when you create the source. You only need to set up a bounding box for that once, and the source will automatically scale itself into the configured space.
Go to the transform settings of a source (right-click, Transform, Edit Transform) and set the Bounding Box Type to Scale to inner bounds. With this setting, the outline of the source you see in the OBS scene is not the content of the source itself anymore, but the bounding box, into which the content will scale and align itself automatically. Under Alignment in bounding box you can also set whether to center, left-align etc. the content.
If you want to use the same bounding box settings for more than one source, you can copy the transform settings with right-click, Transform, Copy/Paste Transform. Even better is to prepare a placeholder element that you can position and size appropriately, and then copy from that. Just make a color source, give it a nice bright color, position and size it to represent your bounding box, then change the transform settings to give it a bounding box with the alignment you want, and then you can copy the transform settings from that placeholder to any source you want to position there.
Another tip that is semi-related to the bounding boxes: The transform settings also contain cropping values. If you need to crop away e.g. the visible parts of an emulator window or something like that, you might set the crop there, but it’s easily lost. Instead, you can add a crop filter to a source. It will not be modified if you change or reset the transform settings, and you can add multiple crop filters to a source, e.g. for different emulators, and enable only the one you currently need. Filters can also easily be copied to other sources, so they’re reusable after configuring them once.
