Overlay one video on top of another.

It takes two inputs and one output, the first input is the "main" video on which the second input is overlayed.

It accepts the parameters: x:y.

x is the x coordinate of the overlayed video on the main video, y is the y coordinate. The parameters are expressions containing the following parameters:

main_w, main_h

main input width and height

W, H

same as main_w and main_h

overlay_w, overlay_h

overlay input width and height

w, h

same as overlay_w and overlay_h

Be aware that frames are taken from each input video in timestamp order, hence, if their initial timestamps differ, it is a a good idea to pass the two inputs through a setpts=PTS-STARTPTS filter to have them begin in the same zero timestamp, as it does the example for the movie filter.

Follow some examples:

# draw the overlay at 10 pixels from the bottom right
# corner of the main video.
overlay=main_w-overlay_w-10:main_h-overlay_h-10

# insert a transparent PNG logo in the bottom left corner of the input
movie=logo.png [logo];
[in][logo] overlay=10:main_h-overlay_h-10 [out]

# insert 2 different transparent PNG logos (second logo on bottom
# right corner):
movie=logo1.png [logo1];
movie=logo2.png [logo2];
[in][logo1]       overlay=10:H-h-10 [in+logo1];
[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]

# add a transparent color layer on top of the main video,
# WxH specifies the size of the main input to the overlay filter
color=red.3:WxH [over]; [in][over] overlay [out]

You can chain togheter more overlays but the efficiency of such approach is yet to be tested.