Memory layout of VK_FORMAT_G8_B8_R8_3PLANE_420_UNORM

Question

I am trying to figure out which memory layout VK_FORMAT_G8_B8_R8_3PLANE_420_UNORM has in Vulkan. What I think I understand:

• each component has 8bits
• the normalized unsigned value for each component is then 0-255

So I would have expected components to be something like G0G1B0R0G2G3B2R2.

Which would satisfy 4:2:0:

• offset of 4
• 2 values for first line at least for G. Though not for B and R.

Getting RGB, planes and 420 combined seems too much for my brain.

Could someone explain how this is supposed to be interpreted.

Answer 1

It is multi-plane image, so basically each component is its own separate image (resp. aspect).

The G plane is image size. The B and R planes are each half width and height.