Does NDI prevent multicast address and port conflicts when using a shared multicast IP pool?

The NDI sender chooses which multicast addresses it will use. Given the netprefix and netmask values, it randomly picks a set of addresses to use. This part is important. It does not pick a single address per sender. It picks multiple addresses.

Ideally, the range defined by the netprefix and netmask is large enough to accommodate usage across the whole network. For example, a network with 32 encoders and a multicast range of 32 addresses would not be sufficient.

NDI does not have a mechanism to avoid conflicts. There is an identifier within the multicast streams themselves, but if two NDI senders choose the same multicast address, the receiving side could potentially subscribe to both streams and then pick out the correct data. This is not ideal, since it would need to receive both streams in order to discard one.