Reporting Width and Height of Compressed Texture Surfaces
When the DirectX runtime requests that a driver create a DXTn compressed texture surface whose width and height are less than 4x4, the driver actually allocates a 4x4 block of memory for the texture surface. However, the driver reports the width and height of the texture surface as the values that the runtime requested. For example, if a 2x2 DXT1 compressed texture surface is requested, the driver allocates a 4x4 block but reports that the block is 2x2 by leaving the requested texture size unchanged. To request a specific DXTn compressed texture size, the runtime sets the dwWidth and dwHeight members of a DDSURFACEDESC or DDSURFACEDESC2 structure that represents the texture surface. The driver does not alter these size settings even if it allocates a 4x4 texture surface when the request is for a texture surface whose width and height are less than 4x4.