Matching cost computation

Theoretical basics

Theory is detailed in the exploring the field section (Matching cost computation).

Configuration and parameters

Table 6 Available parameters

Name	Description	Type	Default value	Available value	Required
matching_cost_method	Similarity measure	string	None	“ssd” “sad” “zncc” “zncc-optim-1” “zncc-optim-2” “zncc_python” “mc_cnn” “mutual_information”	Yes
window_size	Window size for similarity measure	int	5	> 0 and odd or 11 if “matching_cost_method” is “mc_cnn” or >1 if “refinement_method” is “optical_flow”	No
step	Step [row, col] for computing similarity coefficient	list[int, int]	[1, 1]	list[int >0, int >0]	No
subpix	Subpix parameter for computing subpixel disparities	int	1	[1,2,4]	No
float_precision	Precision used to compute cost volumes	string	“float32”	“float32”, “f4”, “f” for all methods “float64”, “f8”, “d” for “zncc” (including “zncc-optim-1” and “zncc-optim-2”) or “mutual_information”	No
spline_order	Spline order used for interpolation when subpix > 1	int	1	> 0 and < 6	No

Note

The order of steps should be [row, col].

Note

Many implementations of zncc are available for matching cost method: two in C++ and one in Python. By default, the C++ zncc is used when using the “zncc” matching cost method, it targets the first kind of optimization. To use either the second kind of optimization or the Python version, enter “zncc-optim-2“ or “zncc_python” respectively as the matching cost method in the configuration file.

Note

In C++, two versions of the “zncc” method are proposed. We recommend to use the first optimization “zncc-optim-1” when all pixels are computed (step is small) and when the disparity range is small. We recommend the second optimization “zncc-optim-2” when an important step is provided and disparity ranges are large.

Note

Current “zncc” version links to “zncc-optim-1”.

Note

To use mc_cnn as matching_cost_method, the MCCNN plugin must be installed first. Install it with:

pip install pandora-plugin-mccnn

See Pandora plugin documentation.

Warning

The subpix parameter can only take values 1, 2 and 4.

Example

{
    "input" :
    {
        // input content
    },
    "pipeline" :
    {
        //...
        "matching_cost":
        {
            "matching_cost_method": "ssd",
            "window_size": 7,
            "step" : [5, 5],
            "subpix": 4,
        },
        //...
    },
    "output":
    {
        //...
    }
}