Is it possible to use system audio as producer?

I need to add individual audio to one channel, some from System Audio, some from line in (mixer–>computer line in), I don’t find a producer for system audio, is it possible, or any workaround for this?
This is used for live stream, all audio source are from micphones–>mixer–>computer line in

I use html with js to input audio from the computer line in ,you can try this web audio api

I just found that FFMpeg can handle system audio using dshow, but not sure if it is supported in CCG, need some test
I use this command , but not seeing my line in on the list
ffmpeg -list_devices true -f dshow -i dummy

play 1-1 dshow://audio="@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{DD1BBD40-C805-4AE1-B62D-C7F7FBE79C71}"

tested, and failed…
got errors

DShow sure used to work in older versions… but it may need a video device as primary input?

And something to keep in mind is that CasparCG can be pretty picky on where you put double quotes. Maybe try

play 1-1 "dshow://audio=\"@device_cm_{33D9A762-90C8-11D0-BD43-00A0C911CE86}\wave_{DD1BBD40-C805-4AE1-B62D-C7F7FBE79C71}\""

the reason I used device location instead of name is that my device are in Chinese which will be show as ???, seems not supported well

then I found that I can edit this name, so I tested again with English device name, it works

play 1-1 “dshow://audio=Line In (Realtek High Definition Audio)”

but I got a new problem
I add system sound output for sound monitor
I speak to the microphone, and then I hear my voice after like 1.5 seconds
Do you have any idea how to fix this delay problem

tested ffplay to play line in, same latency, so it’s not the problem of CCG

anyone have ideas to play system audio in CCG? thanks.

NDI Scan converter?

rrebuffo has a point, but my sugestion is just a different software OBS.
Audio in and mixed in OBS and output as a NDI