I have a streaming app which sending over websockets every 300ms images in base64 to a channel (room). Previously I've used a python server, but under high loads the server crashed. Now I using this config and it works, but I have a problem with echo messages. Every image from app after delivering to nginx sending back to an app, it's generates unnecessary traffic, what is bad for real time. How to avoid echo messages from publisher to itself?

location = /pubsub { 
       nchan_pubsub; 
       nchan_channel_id $arg_r; 
   }