I have A Dahua NVR4216 with the 3.200.0000.9.R firmware. In the setup for camera's under the Codec Tab I see the boxes for audio. This is grayed out and does not give me the ability to check the boxes. The camera is an Axis P3301 with the G726 encoding with a 32bit sample rate. If I go directly to the live view on the camera I can hear the audio perfectly. I have the same problems with a Sony VM601 camera. it seems that the NVR does not give me the ability to check the audio boxes to enable it.