First, let's clarify connecting a NVR/DVR to Angelcam makes sense only if you don't have networking (IP) cameras (otherwise please do connect your cams directly without using NVR/DVR as a middleman, it should be possible in most cases).
For many reasons, it is difficult for us to automatically find a correct stream path. This is usually caused by an incorrect response being sent from a device to us. It results in either a message saying that "we currently don't know the RTSP address for your device", you can be receiving an "Incorrect password" error or you might even get an error code in the player.
In all those cases, it is highly likely that you can still connect your device manually, if you have a correct RTSP address.
The best way to gather your RTSP addresses is to send a request to your device supplier or manufacturer to provide you this information.
If it fails, you can try using the ONVIF Device Manager by following this guide or you can even try asking our support :)
For example, an address for a Dahua NVR looks like this:
You will need to specify the complete address when connecting the device directly (or, when using AngelBox, the bold parts only).
Let's have a look at the individual parameters used in the address above:
Specifies the communication protocol (RTSP is correct in most cases)
Username used for accessing the NVR/DVR
Separates username and password
Separates credentials and address of the NVR/DVR
Actual public (Private when using AngelBox) IP address or hostname of the NVR/DVR
Separates IP address and port
Public port (Private when using AngelBox). For most devices it is a RTSP port, usually 554.
Specific path for the stream. Each manufacturer uses its own.
Separates the path and individual parameters. Not all parameters are necessary in some cases. If you specify just the channel, you will automatically get a primary stream.
This parameter points to a channel number 1, for other channels use channel=2, channel=3 and so on...
Separates individual parameters in the path.
Parameter specifying primary or secondary stream subtype=0 is primary, subtype=1 is secondary (with lower resolution).
In some cases, the structure of the address is a bit different (different characters used as separators and username and password being a part of a parameter. For example:
Where /live=2.2 means a channel number two and a secondary stream, username and password follow as additional parameters.
Please note that addresses for individual IP cameras work in a very similar way.
Alternatively, you can try to find your RTSP address using ONVIF device manager.
Btw, you can avoid all these hassles by using any Angelcam ready brand/model.