Anaglyph is a rather old mechanism to make a 3D stereoscopic effect using color filters for the left and right eyes, e.g. red and cyan. Given two video cameras with proper eye distance which are two distinct v4l2 devices, the [v4l2] extension can be used with its support of loopback devices to make another third virtual anaglyph 3d camera which delivers the red/cyan mixture of the two real cameras. If you use red/cyan glasses when viewing that device's output, you'll see a stereoscopic image. Here is the script: ====== # Make anaglyph of a stereo camera and send # resulting frames into v4l2 loopback device package require v4l2 # Setup loopback device, use YUV here since # jitsi.org in FireFox does not support RGB. v4l2 loopback /dev/video2 YUYV 640 480 25 # Open loopback device for later writes set loop [v4l2 open /dev/video2 #no-image-callback] # Callback: image ready or error proc image_callback {dev ind} { if {$ind eq "error"} { puts stderr "acquisition error, exiting" set ::forever 0 } # Fetch image set n $::devs($dev) set ::imgs($n) [v4l2 image $dev] # When both images available, combine to anaglyph # and output on loopback device catch { lassign $::imgs(0) width0 height0 bpp0 img0 lassign $::imgs(1) width1 height1 bpp1 img1 v4l2 mbcopy $img1 $img0 0x00ff0000 if {$n == 1} { v4l2 write $::loop $img1 } } } # Initialize cameras proc init_cameras {} { set count 0 # Find cameras by friendly name foreach name [glob -nocomplain /dev/v4l/by-id/*Stereo_Vision*] { set dev [v4l2 open $name image_callback] # Use MJPEG, otherwise USB 2.0 bandwidth is insufficient v4l2 parameters $dev frame-rate 25 frame-size 640x480@MJPG set ::devs($dev) $count incr count if {$count > 1} { break } } if {$count != 2} { puts stderr "need two cameras" exit 1 } # Start both cameras foreach dev [array names ::devs] { v4l2 start $dev } } init_cameras # Need an event loop for operation vwait forever ====== What is it good for? By using the loopback device, I will hopefully be 3-dimensional in the next virtual [TUGM] meeting for which we use https://meet.jit.si%|%Jitsi%|%.