Parameters

Disparity pre-filtering

~prefilter_size (int, default: 9)

• Normalization window size, pixels.

~prefilter_cap (int, default: 31)

• Bound on normalized pixel values.

Disparity correlation

~correlation_window_size (int, default: 15)

• Edge size (pixels) of the correlation window for matching. Values must be odd, in the range 5 to 255 (but with an extra performance hit for values larger than 21). Larger values have smoother disparity results, but smear out small features and depth discontinuities.

~min_disparity (int, default: 0)

• Minimum disparity, or the offset to the disparity search window. By setting to a positive value, the cameras become more "cross-eyed" and will find objects closer to the cameras. If the cameras are "verged" (inclined toward each other), it may be appropriate to set min_disparity to a negative value. When min_disparity is greater than 0, objects at large distances will not be found.

~disparity_range (int, default: 64)

• The size of the disparity search window (pixels). Together with min_disparity, this defines the "horopter," the 3D volume that is visible to the stereo algorithm.

Disparity post-filtering

~uniqueness_ratio (double, default: 15.0)

• Filters disparity readings based on a comparison to the next-best correlation along the epipolar line. Matches where uniqueness_ratio > (best_match - next_match) / next_match are filtered out.

~texture_threshold (int, default: 10)

• Filters disparity readings based on the amount of texture in the correlation window.

~speckle_size (int, default: 100)

• Filters disparity regions that are less than this number of pixels. For example, a value of 100 means that all regions with fewer than 100 pixels will be rejected.

~speckle_range (int, default: 4)

• Groups disparity regions based on their connectedness. Disparities are grouped together in the same region if they are within this distance in pixels.

Synchronization

~approximate_sync (bool, default: false)

• Whether to use approximate synchronization. Set to true if the left and right cameras do not produce exactly synced timestamps.

~queue_size (int, default: 5)

• Size of message queue for each synchronized topic. You may need to raise this if images take significantly longer to travel over the network than camera info and/or the delay from disparity processing is too long.