Also, I notice that if you switch the format of the texture that you stream the video to to pc.PIXELFORMAT_R8_G8_B8, the cost of texImage2D falls dramatically. This will use twice the VRAM as pc.PIXELFORMAT_R5_G6_B5, but presumably, pixel conversions don’t have to be performed on the CPU (because the video pixel data is already 888).
However, notice that it’s still running at 30FPS (on my machine). The reason seems to be because the GPU is still having to do a lot of work. Investigating…