I have an Nvidia Shield TV that I use to stream BigBox to my Sony Bravia TV from my gaming PC via Nvidia GameStream. It works great with one exception. GameStream defaults to the 2560 x 1080 resolution of my ultra widescreen monitor. This causes unnecessary letterboxing that does not allow BigBox or any emulators that are launched by BigBox to use all of my TV screen real estate. In order to prevent this I had been manually changing the resolution to 1920 x 1080 before running BigBox. This was super annoying, so I contacted Unbroken Software support to find out if BigBox supported automatically changing the display's resolution allowing BigBox to run with a 16:9 aspect ratio on my TV. Unfortunately, the answer was no, but I knew there had to be a better way. Enter Google...
I found a great little utility for Windows called QRes. QRes supports changing desktop resolutions from the command line. With this utility and some helpful posts on StackOverflow.com, I managed to write a batch file to accomplish my goal:
Minimize the command window
Change the resolution to 1920 x 1080 via QRes
Wait for the BigBox process to terminate
Change the resolution back to 2560 x 1080 via QRes
I have attached my batch file and the QRes utility. Simply unzip both to your LaunchBox root directory. If your ultra widescreen monitor uses a resolution other than 2560 x 1080, edit the last line of the batch file to meet your requirements. Then add BigBox.bat as a GameStream game in Nvidia GeForce Experience.