In your configuration example you refer to a channel list if the nvr can't retrieve that.
Is this list 0 based even if the first camera is indexed as 1 on nvr?
Example of a camera routed by the nvr:
mjpeg_url: "http://IP_NUMBER/cgi-bin/mjpg/video.cgi?channel=1&subtype=1"
This implementation is working fine but the channel list are starting at 1 not 0.