Mixer command on server start


Hi there,

I am running content to an LED screen. The output from Caspar is going straight into the LED processor and there is no scaler in the chain, so we need to scale the content down to match the LED.

We can do this in caspar using a Mixer Fill command - mixer 1-1 fill 0 0 0.25 0.25, but I am wondering if it is possible to have this command run on server startup?

I’ve seen in 2.1 NRK there is the mixer section in the config file, but am unsure if/how it can run the fill command.
I also see there is producers section that can play a video on a layer on start. I’ve tried putting the fill command in this but unfortunately does not work.

casparcg.config options
    <blend-modes>          false [true|false]</blend-modes>
    <mipmapping-default-on>false [true|false]</mipmapping-default-on>
    <straight-alpha>       false [true|false]</straight-alpha>
    <producer id="0">AMB LOOP</producer>
    <producer id="10">DECKLINK DEVICE 2</producer>

Thanks in advance,


In 2.0.7 you can do this by redirecting a file of commands to your server:

casparcg.exe < startup.txt

Remember to end with a blank line.

In later versions this doesn’t work, because EOF is now interpreted as EXIT and so it reads your commands then quits.

in windows the more complicated line works:

TYPE startup.txt CON 2>NUL | casparcg.exe

Again remember to end your startup.txt with a blank line.


Bare in mind that when casparcg.exe exits, TYPE is still running and so this may require special handling in scripts.


In this launcher you have the option to send commands to the server on startup.