Hi Louis,
Our Suggestion is doing the YUV to RGB using the IPU CSC if you have a single layer overlay since it's done on the fly. however Please check sect.2.4.1 Color space conversion from YUV to RGB in your i.MX_6_Graphics_User's_Guide.pdf and sect.7.3.15 Video conversion Linux Guide of the Linux user bsp guide:
https://community.nxp.com/servlet/JiveServlet/download/833793-1-393244/i.MX_Linux_User's_Guide.pdf
For samples You can download gpu_sdk from nxp website:
Regards