I have four videos that I would like to tile in a 2x2 fashion to make a new video. Is there a way I can do this easily, preferably free and under Linux? I am willing to program a moderate amount, perhaps in order to interact with some library, but unwilling to write an entire video-processing program myself. You may assume that the input and output videos are in whatever commonly-occurring format is most convenient.
An analogue of the gm montage command (for images) would be fantastic.
I am currently using GStreamer for a similar project (lecture-capture) myself. You are probably looking for the videomixer element. Check out this example: Video 4-way split screen gstreamer pipeline (script is located here).
GStreamer works perfectly fine on Windows too. You may want to check out the GStreamer WinBuilds if you are interested.
Example
Here's a basic script that works for me on Windows (it doesn't have the backslashes because I use the gst_parse_launch call from C code to parse the pipeline description):
v0. ! queue
! decodebin
! ffmpegcolorspace
! videoscale
! video/x-raw-yuv,width=320,height=240
! videobox right=-320 bottom=-240
! ffmpegcolorspace
! vmix.sink_0
v1. ! queue
! decodebin
! ffmpegcolorspace
! videoscale
! video/x-raw-yuv,width=320,height=240
! videobox bottom=-240
! ffmpegcolorspace
! vmix.sink_1
v2. ! queue
! decodebin
! ffmpegcolorspace
! videoscale
! video/x-raw-yuv,width=320,height=240
! videobox right=-240
! ffmpegcolorspace
! vmix.sink_2
v3. ! queue
! decodebin
! ffmpegcolorspace
! videoscale
! video/x-raw-yuv,width=320,height=240
! ffmpegcolorspace
! vmix.sink_3
vmix. ! queue
! ffmpegcolorspace
! dshowvideosink
filesrc location="c:/test.mpg" name="v0"
filesrc location="c:/test.mpg" name="v1"
filesrc location="c:/test.mpg" name="v2"
filesrc location="c:/test.mpg" name="v3"
videomixer name=vmix
sink_0::xpos=0 sink_0::ypos=0 sink_0::zorder=0
sink_1::xpos=320 sink_1::ypos=0 sink_1::zorder=1
sink_2::xpos=0 sink_2::ypos=240 sink_2::zorder=2
sink_3::xpos=320 sink_3::ypos=240 sink_3::zorder=3