I am working on a project using TI 365 DSP. There is an annoying issue of OSD transparency working in YUV422 mode. YUV422 is a packed format and the OSD transparency implementation knocks out only Y field by the provided transparency value, so if you want to have a rectangle drawn on such surface - the borders of it look ugly.
Have anyone dealt with this and maybe have a solution?
I avoided using YUV422 for the OSD due to the transparency requirements that I had. You could try seeing if using an Attribute window helps in your situation.
Also, I had a lot of per-pixel alpha that didn't look right without blending, so I eventually settled on using the RGB888 mode that has 3 bits of alpha. I don't know how much of the screen that you'll need for your OSD window, but I saw memory bus issues when it was 1280x720. Luckily, I only needed a small portion of the screen, and the RGB888 mode worked well for that.