VLC HowTo/Make a mosaic

This page describes how to set up a mosaic of a few videos or stream like a TV portal.

Other "how to" pages

VLC mosaic howto

This is a small example about how to use VLC media player to create a mosaic. What we basically want is a video mosaic mixing 3 video channels (channels 1, 2 and 3) on a background image (background.png) and streaming the resulting video on the network. Note that we will also be streaming the 3 sound tracks from channels 1, 2 and 3 in the same MPEG-TS stream.

Starting with VLC 0.8.5-test2, the HTTP interface features a "Mosaic wizard". You might want to use it if you have no knowledge of VLC command line usage.

Other neat examples :

• 12 video mosaic
• 20 video mosaic
• 20 video mosaic

Step 0

Read the VLC streaming howto^[fr] (chapters 3^[fr] and 5^[fr] concerning command line and VLM usage in VLC) : www.videolan.org/doc

Step 1

Get VLC 2 or newer and install it on your computer.

Step 2

You now have to get a background for the mosaic.

An image is the easiest way to have a background that can be played as long as necessary. The image should be the same size as the video you want to create. Many image formats are supported (JPEG, PNG …).

It is also possible to use a video as a background for the mosaic, and superimpose other videos.

The frame rate of the background video or image will be the frame rate of the mosaic video. This is important since the default frame rate for image files is 10fps.

For videolan 1.x and earlier, use the fake: access method. The frames per second cannot be changed.

You should test it with VLC to see if it displays locally :

./vlc file:///full/path/to/background.png --image-duration=-1 --image-fps=10

Step 3

You now need to configure VLC to get the 3 source streams and blend them on the background image.

The VLM configuration file looks like :

new channel1 broadcast enabled                                                       
setup channel1 input udp://@239.255.2.60:1234                                        
setup channel1 output #duplicate{dst=mosaic-bridge{id=1,height=144,width=180},select=video,dst=bridge-out{id=1},select=audio}                                                         
                                                                                
new channel2 broadcast enabled
setup channel2 input udp://@239.255.10.200:1234
setup channel2 output #duplicate{dst=mosaic-bridge{id=2,height=144,width=180},select=video,dst=bridge-out{id=2},select=audio}                                                         

new channel3 broadcast enabled
setup channel3 input udp://@239.255.6.9:1234
setup channel3 output #duplicate{dst=mosaic-bridge{id=3,height=144,width=180},select=video,dst=bridge-out{id=3},select=audio}                                                         

new background broadcast enabled
setup background input /full/path/to/background.png
setup background output #transcode{sfilter=mosaic,vcodec=mp2v,vb=10000,scale=1}:bridge-in{delay=400,id-offset=100}:standard{access=udp,mux=ts,url=239.255.12.42,sap,name="mosaic"}

control background play
control channel1 play
control channel2 play
control channel3 play

Since VLC 2.0, the mosaic options must be passed in the command line, and not in the VLM file.

Alternatively, one can setup a mosaic directly from files using a VLM configuration file as the following :

new channel1 broadcast enabled                                                       
setup channel1 input file:///path/to/movie.mp4
setup channel1 output #duplicate{dst=mosaic-bridge{id=1,height=366}} 
                                            
new channel2 broadcast enabled                                                       
setup channel2 input file:///path/to/movie.mp4
setup channel2 output #duplicate{dst=mosaic-bridge{id=2,height=366}}

new channel3 broadcast enabled                                                       
setup channel3 input file:///path/to/movie.mp4
setup channel3 output #duplicate{dst=mosaic-bridge{id=3,height=366}}

new channel4 broadcast enabled                                                       
setup channel4 input file:///path/to/movie.mp4
setup channel4 output #duplicate{dst=mosaic-bridge{id=4,height=366}}
                                 
new mosaic broadcast enabled
setup mosaic input file:///path/to/background1600.png
setup mosaic output #transcode{sfilter=mosaic,vcodec=mp4v,VB=20000,acodec=none,fps=15,scale=1}:display

control mosaic play
control channel1 play
control channel2 play
control channel3 play
control channel4 play

To write the resulting stream to a file, the mosaic output line may also be replaced by :

setup mosaic output #transcode{sfilter=mosaic,vcodec=mp4v,VB=20000,acodec=none,fps=15,scale=1}:standard{access=file,mux=ogg,dst="output_file.ogg"}

Note that the source streams are network streams, which is likely to be the case if you're considering doing a mosaic.

Step 4

And now, the right command to launch VLC :

./vlc --color -I telnet --vlm-conf --mosaic-width=360 --mosaic-height=288 --mosaic-keep-picture --mosaic-rows=2 --mosaic-cols=2 --mosaic-position=1 --mosaic-order=1,2,3,4 ../mosaic.vlm.conf --ttl 12 --udp-caching 800

Other examples

Dual webcam with alphamask

See also: Documentation:Modules/alphamask

new isight broadcast
setup isight input v4l2:///dev/video0:width=320:height=240:audio-method=0
setup isight option v4l2-brightness=90
setup isight output #mosaic-bridge{chroma=YUVA,vfilter=alphamask{mask=../mask.png},width=320,height=240}
setup isight enabled

new logitech broadcast
setup logitech input v4l2:///dev/video1:width=640:height=480:audio-method=0
setup logitech output #transcode{vcodec=mp4v,vb=1024,sfilter="mosaic:marq{marquee='VLC dual webcam setup',position=8}"}:bridge-in:display
setup logitech enabled

new audio broadcast enabled
setup audio input v4l:///dev/dsp1
setup audio output #transcode{acodec=mp4a,ab=128}:bridge-out

control isight play
#control audio play
control logitech play

You can then launch it with :

vlc --vlm-conf ../dual-webcam.conf --no-media-library --plugin-path modules -v --no-video-title --mosaic-keep-picture

The mask.png file is used to set transparency values on the isight camera (uses the png alpha plane). An example file to use is available at people.videolan.org/~dionoea/mosaic.

See also

• Diagram that might help
• VLC mosaic-related resources
• Example set-up of conference web-streaming with two grabber cards

Appendix

• Documentation:Modules/mosaic
• Documentation:Modules/mosaic-bridge
• Documentation:Modules/bridge-out
• Documentation:Modules/bridge-in

Mosaic specific video filters

• Documentation:Modules/alphamask
• Documentation:Modules/bluescreen