Subtract

Show the difference between two clips. Where the clips are equal, the output is 50% grey.
See filters with multiple input clips for the resulting clip properties.

Syntax

Subtract(clip clip1, clip clip2)

Examples

Show the difference between two clips, and make the difference blatantly obvious:

Subtract(A, B).Levels(65, 1, 255-64, 0, 255, coring=false)

Show the difference between adjacent frames:

Subtract(A, A.Trim(1, 0))

About offset of luma range

For YUV formats the valid Y range is 16-235, and Subtract takes this into account. This means that the following script

Subtract(A, B)

...will result in a "50% grey" clip with luma=126.

If you require a mathematically correct subtract function for 0-255 RGB or YUV data, use Overlay:

Overlay(A, B, mode="difference", pc_range=false)

...which results in a "50% grey" clip with luma=128.