Add note about requesting multiple backchannel on Dahua Doorbell

README.md

@@ -231,7 +231,7 @@ streams:
   sonoff_camera: rtsp://rtsp:12345678@192.168.1.123/av_stream/ch0
   dahua_camera:
     - rtsp://admin:password@192.168.1.123/cam/realmonitor?channel=1&subtype=0&unicast=true&proto=Onvif
-    - rtsp://admin:password@192.168.1.123/cam/realmonitor?channel=1&subtype=1
+    - rtsp://admin:password@192.168.1.123/cam/realmonitor?channel=1&subtype=1#backchannel=0
   amcrest_doorbell:
     - rtsp://username:password@192.168.1.123:554/cam/realmonitor?channel=1&subtype=0#backchannel=0
   unifi_camera: rtspx://192.168.1.123:7441/fD6ouM72bWoFijxK
@@ -241,7 +241,7 @@ streams:
 **Recommendations**
 
 - **Amcrest Doorbell** users may want to disable two way audio, because with an active stream you won't have a call button working. You need to add `#backchannel=0` to the end of your RTSP link in YAML config file
-- **Dahua Doorbell** users may want to change backchannel [audio codec](https://github.com/AlexxIT/go2rtc/issues/52)
+- **Dahua Doorbell** users may want to change backchannel [audio codec](https://github.com/AlexxIT/go2rtc/issues/52). Make sure not to request backchannel multiple times by adding `#backchannel=0` to other stream sources of the same doorbell
 - **Reolink** users may want NOT to use RTSP protocol at all, some camera models have a very awful unusable stream implementation
 - **Ubiquiti UniFi** users may want to disable HTTPS verification. Use `rtspx://` prefix instead of `rtsps://`. And don't use `?enableSrtp` [suffix](https://github.com/AlexxIT/go2rtc/issues/81)
 - **TP-Link Tapo** users may skip login and password, because go2rtc support login [without them](https://drmnsamoliu.github.io/video.html)