Generates flow vectors in X and Y direction in S10.5 format at quarter pixel precision for 8-bit contents. The vectors are provided for 4x4 grid size.

Please give insight on following:

  1. S10.5 format
  2. 8-bit content.Does this mean 8bit per channel that is R8G8B8A8?
  3. 4x4 grid size.Does this mean 16 neighbouring pixels?

Hi.

  1. S10.5 is fixed pointer representation of a 16-bit number used to represent our motion vectors. MSB specifies the sign bit of the flow vector, Next 10 bits specify the integer value of the flow vector.
    And Last 5 bits represents fractional value of the flow vector. Note that, though we are using 5 bits for fractional value, we only support quarter pixel precision. It means, of the 5 available bits, only 2 bits are used.
    A simple article explaining fixed-point representation and conversion: http://www-inst.eecs.berkeley.edu/~cs61c/sp06/handout/fixedpt.html

  2. 8-bit content means: each channel has a bit depth of 8 bits. This applies to all input formats supported by NVOF API. Just FYI, NVOF API supports Y8, NV12 and A8B8G8R8.

  3. 4x4 grid size means a square block of 4x4 pixels. Assume the below image to have 16x16 pixels. Each square is a grid(of size 4x4).

Thanks.