Try one of SDL2's YUV pixel formats.
They have several planar and packed variants:
SDL_PIXELFORMAT_YV12
: planar mode: Y + V + U (3 planes)
SDL_PIXELFORMAT_IYUV
: planar mode: Y + U + V (3 planes)
SDL_PIXELFORMAT_YUY2
: packed mode: Y0+U0+Y1+V0 (1 plane)
SDL_PIXELFORMAT_UYVY
: packed mode: U0+Y0+V0+Y1 (1 plane)
SDL_PIXELFORMAT_YVYU
: packed mode: Y0+V0+Y1+U0 (1 plane)